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6. November 2013

 

Now we are going to look quickly at using a camera, something we haven’t used in any of the prior tutorials.  Using a camera has a couple of advantages.  It gives you an easier way of dealing with device resolution as LibGDX will scale the results up to match your device resolution.  It also makes it easier to move the view around when your scene is larger than a single screen.  That is exactly what we are going to do in the code example below.

 

I am using a large ( 2048x1024 ) image that I obtained here.

 

Alright, now the code:

package com.gamefromscratch;

import com.badlogic.gdx.ApplicationListener;

import com.badlogic.gdx.Gdx;

import com.badlogic.gdx.graphics.GL10;

import com.badlogic.gdx.graphics.OrthographicCamera;

import com.badlogic.gdx.graphics.Texture;

import com.badlogic.gdx.graphics.Texture.TextureFilter;

import com.badlogic.gdx.graphics.g2d.Sprite;

import com.badlogic.gdx.graphics.g2d.SpriteBatch;

import com.badlogic.gdx.input.GestureDetector;

import com.badlogic.gdx.input.GestureDetector.GestureListener;

import com.badlogic.gdx.math.Vector2;

public class CameraDemo implements ApplicationListener, GestureListener {

private OrthographicCamera camera;

private SpriteBatch batch;

private Texture texture;

private Sprite sprite;

@Override

public void create() {

   camera = new OrthographicCamera(1280, 720);

   batch = new SpriteBatch();

   texture = new Texture(Gdx.files.internal("data/Toronto2048wide.jpg"));

   texture.setFilter(TextureFilter.Linear, TextureFilter.Linear);

   sprite = new Sprite(texture);

   sprite.setOrigin(0,0);

   sprite.setPosition(-sprite.getWidth()/2,-sprite.getHeight()/2);

   Gdx.input.setInputProcessor(new GestureDetector(this));

}

@Override

public void dispose() {

   batch.dispose();

   texture.dispose();

}

@Override

public void render() {

   Gdx.gl.glClearColor(1, 1, 1, 1);

   Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT);

   batch.setProjectionMatrix(camera.combined);

   batch.begin();

   sprite.draw(batch);

   batch.end();

}

@Override

public void resize(int width, int height) {

}

@Override

public void pause() {

}

@Override

public void resume() {

}

@Override

public boolean touchDown(float x, float y, int pointer, int button) {

// TODO Auto-generated method stub

return false;

}

@Override

public boolean tap(float x, float y, int count, int button) {

// TODO Auto-generated method stub

return false;

}

@Override

public boolean longPress(float x, float y) {

// TODO Auto-generated method stub

return false;

}

@Override

public boolean fling(float velocityX, float velocityY, int button) {

// TODO Auto-generated method stub

return false;

}

@Override

public boolean pan(float x, float y, float deltaX, float deltaY) {

   // TODO Auto-generated method stub

   camera.translate(deltaX,0);

   camera.update();

   return false;

}

@Override

public boolean zoom(float initialDistance, float distance) {

// TODO Auto-generated method stub

return false;

}

@Override

public boolean pinch(Vector2 initialPointer1, Vector2 initialPointer2,

Vector2 pointer1, Vector2 pointer2) {

// TODO Auto-generated method stub

return false;

}

}

 

Additionally in Main.java I changed the resolution to 720p like so:

package com.gamefromscratch;

import com.badlogic.gdx.backends.lwjgl.LwjglApplication;

import com.badlogic.gdx.backends.lwjgl.LwjglApplicationConfiguration;

public class Main {

   public static void main(String[] args) {

      LwjglApplicationConfiguration cfg = new LwjglApplicationConfiguration();

      cfg.title = "camera";

      cfg.useGL20 = false;

      cfg.width = 1280;

      cfg.height = 720;

      new LwjglApplication(new CameraDemo(), cfg);

   }

}

When you run it you will see:

SS

 

Other then being an image of my cities skyline, its pan-able. You can swipe left or right to pan the image around.

 

The code is mostly familiar at this point, but the important new line is:

camera = new OrthographicCamera(1280, 720);

This is where we create the camera.  There are two kinds of cameras in LibGDX, Orthographic and Perspective.  Basically an orthographic camera renders what is in the scene exactly the size it is.  A perspective camera on the other hand emulates the way the human eye works, by rendering objects slightly smaller as they get further away.  Here is an example from my Blender tutorial series.

 

Perspective:

Perspective

Orthographic:

Orthographic

 

Notice how the far wing is smaller in the perspective render?  That’s what perspective rendering does for you.  In 2D rendering however, 99 times out of 100 you want to use Orthographic.

 

The values passed to the constructor are the resolution of the camera, the width and height.  In this particular case I chose to use pixels for my resolution, as I wanted to have the rendering at 1280x720 pixels.  You however do not have to… if you are using physics and want to use real world units for example, you could have gone with meters, or whatever you want.  The key thing is that your aspect ratio is correct.  The rest of the code in create() is about loading our image and positioning it about the origin in the world.  Finally we wire up our gesture handler so we can pan/swipe left and right on the image.

 

The next important call is in render():

batch.setProjectionMatrix(camera.combined);

This ties our LibGDX camera object to the OpenGL renderer.  The OpenGL rendering process depends on a number of matrix to properly translate from the scene or world to screen coordinates during rendering.  camera.combined returns the camera’s view and projection matrixes multiplied together.  If you want more information about the math behind the scenes you can read here.  Of course, the entire point of the Camera classes is so you don’t have to worry about this stuff, so if you find it confusing, don’t sweat it, LibGDX takes care of the math for you. 

Finally in our pan handler ( huh? ) we have the following code:

camera.translate(deltaX,0);

camera.update();

 

You can use translate to move the camera around. Here we move the camera along the X axis by the amount the user swiped. This causes the view of the image to move as the user swipes the screen/pans the mouse. Once you are done modifying the camera, you need to update it. Without calling update() the camera would never move.

There are a number of neat functions in the camera that we don’t use here.  There are functions to look at a point in space, to rotate or even rotate around ( orbit ) a vector.  There are also functions for projecting to and from screen to world space as well as code for ray casting into the scene.  In a straight 2D game though you generally won’t use a lot of this functionality.  We may take a closer look at the camera class later on when we jump to 3D.

Programming


3. November 2013

There was a new LibGDX release today, new features include:

  • 3D API.  This one has been in the works for some time and brings 3D to LibGDX built over OpenGL 2.0 ES.  Click here for more information on 3D support.
  • iOS back end moved from Xamarin’s MonoTouch to ROBOVM.  No more $300 charge to support iOS!
  • Updates to LWJGL, box2D and Bullet Physics libraries to the latest stable releases.
  • Android x86 support.  Beyond the contest not sure the win here.  Faster emulation?
  • LibGDX added to maven ( com.badlogicgames.libgdx ).
  • Gradle build option… is this one step away from the insanity that is Eclipse?  I sure hope so!
  • Small bug fixes and improvements.  See the list here.

 

LibGDX test of shader with skinning:

LibGDX bullet physics on iOS using ROBOVM

 

You can read more about the release here.

News


30. October 2013

 

In the previous tutorial we looked at handling touch and gesture events.  These days, most mobile devices have very accurate motion detection capabilities, which LibGDX fully supports.  In this example we will look at how to handle motion as well as detect if a device supports certain functionality and to detect which way the device is oriented.

 

This project revolves around a single code example, but there are some configuration steps you need to be aware of.

 

First off, in order to tell LibGDX that you want to use the compass and accelerometer, you need to pass that as part of the configuration in your Android MainActivity.  In the android project locate MainActivity.java and edit it accordingly:

package com.gamefromscratch;

import android.os.Bundle;

import com.badlogic.gdx.backends.android.AndroidApplication;

import com.badlogic.gdx.backends.android.AndroidApplicationConfiguration;

public class MainActivity extends AndroidApplication {

    @Override

    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

       

        AndroidApplicationConfiguration cfg = new AndroidApplicationConfiguration();

        cfg.useGL20 = true;

        cfg.useAccelerometer = true;

        cfg.useCompass = true;

       

        initialize(new MotionDemo(), cfg);

    }

}

 

The meaningful lines are

cfg.useAccelerometer = true;

and

cfg.useCompass = true;

 

These lines tell LibGDX to enable both.

Next we need to make a couple of changes to your Android manifest.  This is a configuration file of sorts that tells the Android operating system how your application performs and what permissions it requires to run.  You could literally write an entire book about dealing with Android manifests, so if you want more information read here.  The manifest is located at the root of your Android project and is called AndroidManifest.xml.  There are a couple ways you can edit it.  Simply right click AndroidManifest.xml and select Open With->.

ManifestEditAs

 

I personally prefer to simply edit using the Text Editor, but if you want a more guided experience, you can select Android Manifest Editor, which brings up this window:

Java motion android AndroidManifest xml Eclipse Users Mike Dropbox Workspace

This is basically a GUI layer over top of the Android manifest.  Using the tabs across the bottom you can switch between the different categories and a corresponding form will appear.  If you click AndroidManifest.xml it will bring up a text view of the manifest.  Use whichever interface you prefer, it makes no difference in the end.

There are two changes we want to make to the manifest.  First we want the device to support rotation, so if the user rotates their device, the application rotates accordingly.  This is done by setting the property android:screenOrientation to fullsensor.  Next we want to grant the permission android.permission.VIBRATE.  If you do not add this permission calling a vibrate call will cause your application to crash!

 

Here is how my manifest looks with changes made:

<?xml version="1.0" encoding="utf-8"?>

<manifest xmlns:android="http://schemas.android.com/apk/res/android"

    package="com.gamefromscratch"

    android:versionCode="1"

    android:versionName="1.0" >

    <uses-sdk android:minSdkVersion="5" android:targetSdkVersion="17" />

    <uses-permission android:name="android.permission.VIBRATE"/>

    <application

        android:icon="@drawable/ic_launcher"

        android:label="@string/app_name" >

        <activity

            android:name=".MainActivity"

            android:label="@string/app_name"

            android:screenOrientation="fullSensor"

            android:configChanges="keyboard|keyboardHidden|orientation|screenSize">

            <intent-filter>

                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />

            </intent-filter>

        </activity>

    </application>

</manifest>

The changes have been bolded above.  You want to be careful when you request additional permissions as they will be shown when the user installs your application.  Too many permissions and people start getting scared of your application.  Of course, if you need to do something that requires a permission there isn’t much you can do!  As to the screenOrientation value, this tells Android which direction to create your application as.  There are a number of options, Landscape and Portrait being two of the most common.  fullSensor basically means all directions supported.  This means you can rotate the device 360 degrees and it will be rotated accordingly.  On the other hand, if you select “user”, you cannot rotate the device 180 degrees, meaning you cannot use it upside down.  You can read more about the available properties in the link I provided earlier.

There is one last important thing to be aware of before moving on.  Your android project will actually have two AndroidManifest.xml files, one in the root directory another in the bin subfolder.  Be certain to use the one in the root directory, as the other one will be copied over!

 

Ok, now that we are fully configured, let’s jump into the code sample:

package com.gamefromscratch;

import com.badlogic.gdx.ApplicationListener;

import com.badlogic.gdx.Gdx;

import com.badlogic.gdx.Input.Orientation;

import com.badlogic.gdx.Input.Peripheral;

import com.badlogic.gdx.graphics.Color;

import com.badlogic.gdx.graphics.GL10;

import com.badlogic.gdx.graphics.g2d.BitmapFont;

import com.badlogic.gdx.graphics.g2d.SpriteBatch;

public class MotionDemo implements ApplicationListener {

private SpriteBatch batch;

private BitmapFont font;

private String message = "Do something already!";

private float highestY = 0.0f;

@Override

public void create() {

   batch = new SpriteBatch();

   font = new BitmapFont(Gdx.files.internal("data/arial-15.fnt"),false);

   font.setColor(Color.RED);

}

@Override

public void dispose() {

   batch.dispose();

   font.dispose();

}

@Override

public void render() {

   int w = Gdx.graphics.getWidth();

   int h = Gdx.graphics.getHeight();

   Gdx.gl.glClearColor(1, 1, 1, 1);

   Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT);

   batch.begin();

   int deviceAngle = Gdx.input.getRotation();

   Orientation orientation = Gdx.input.getNativeOrientation();

   float accelY = Gdx.input.getAccelerometerY();

   if(accelY > highestY)

      highestY = accelY;

   message = "Device rotated to:" + Integer.toString(deviceAngle) + " degrees\n";

   message += "Device orientation is ";

   switch(orientation){

      case Landscape:

         message += " landscape.\n";

         break;

      case Portrait:

         message += " portrait. \n";

         break;

      default:

         message += " complete crap!\n";

         break;

   }

 

   message += "Device Resolution: " + Integer.toString(w) + "," + Integer.toString(h) + "\n";

   message += "Y axis accel: " + Float.toString(accelY) + " \n";

   message += "Highest Y value: " + Float.toString(highestY) + " \n";

   if(Gdx.input.isPeripheralAvailable(Peripheral.Vibrator)){

      if(accelY > 7){

         Gdx.input.vibrate(100);

      }

   }

   if(Gdx.input.isPeripheralAvailable(Peripheral.Compass)){

      message += "Azmuth:" + Float.toString(Gdx.input.getAzimuth()) + "\n";

      message += "Pitch:" + Float.toString(Gdx.input.getPitch()) + "\n";

      message += "Roll:" + Float.toString(Gdx.input.getRoll()) + "\n";

   }

   else{

      message += "No compass available\n";

   }

   font.drawMultiLine(batch, message, 0, h);

   batch.end();

}

@Override

public void resize(int width, int height) {

   batch.dispose();

   batch = new SpriteBatch();

   String resolution = Integer.toString(width) + "," + Integer.toString(height);

   Gdx.app.log("MJF", "Resolution changed " + resolution);

}

@Override

public void pause() {

}

@Override

public void resume() {

}

 

}

 

When you run this program on a device, you should see:

Appresults

 

As you move the device, the various values will update.  If you raise your phone to be within about 30 degrees of completely upright it will vibrate.  Of course, this assumes that your device supports all these sensors that is!

 

The code itself is actually remarkably straight forward, LibGDX makes working with motion sensors remarkably easy, its just actually understanding the returned values that things get a bit more complicated.  The vast majority of the logic is in the render() method.  First we get the angle the device is rotated in.  This value is in degrees with 0 being straight in front of you parallel to your face.  One important thing to realize is this value will always have 0 as up, regardless to if you are in portrait or landscape mode.  This is something LibGDX does to make things easier for you, but is different behaviour than the Android norm.

Next we get the orientation of the device.  Orientation can be either landscape or portrait (wide screen vs tall screen).  Next we check the value of the accelerometer along the Y access using getAccelerometerY().  You can also check the accelerometer for movement in the X and Z axis using getAcceleromterX() and getAcceleromterZ() respectively.  Once again, LibGDX standardizes the axis directions, regardless to the devices orientation.  Speaking of which, Y is up.  The means if you hold your phone straight in front of you parallel to your face, the Y axis is what you would traditionally think of as up and down.  The Z axis would be in front of you, so if you made a push or pulling motion, this would be along the Z axis.  The X axis would track movements to the left and right.

So then, what exactly are the values returned by the accelerometer?  Well this part gets a bit confusing, as it measures both speed and position in a way.  If you hold your phone straight out in front of you, with the screen parallel to your face, it will return a value of 9.8.  That number should look familiar to you, it’s the speed a body falls due to gravity in meters per second.  Therefore if your phone is stationary and upright, its 9.8.  If you move the phone up parallel to your body, the value will rise above 9.8, the amount depends on how fast your are moving the phone.  Moving down on the other hand will return a value below 9.8.  If you put the phone down flat on a desk it will instead return 0. Flipping the phone upside down will instead return -9.8 if held stationary.  Obviously the same occurs along the X and Z axis, but instead that would indication motion left and right or in and out instead of up and down.

Ok, back to our code.  We check to see if the current accelY value is the highest and if it is, we record it to display.  Next we check what value the orientation returned and display the appropriate message.  We dump some information we’ve gathered out to be displayed on screen.  Next we make the very important call Gdx.input.isPeripheralAvailable().  This will return true if the users device supports the requested functionality.  First we check to see if the phone supports vibrating and if it does, we check if the phone is over 7.  Remember the value 9.8 represents straight up and down, so if its 7 or higher its within about 35 degrees of vertical.  If it is, we vibrate by calling vibrate(), the value passed is the number of milliseconds to vibrate for.

Next we check to see if the device has a compass.  If it does, you can check the position of the device relative to polar north.  Here are the descriptions of each value from Google’s documentation:

Azimuth, rotation around the Z axis (0<=azimuth<360). 0 = North, 90 = East, 180 = South, 270 = West
Pitch, rotation around X axis (-180<=pitch<=180), with positive values when the z-axis moves toward the y-axis.
Roll, rotation around Y axis (-90<=roll<=90), with positive values when the z-axis moves toward the x-axis.

You can read more about it here.

Finally we draw the message we have been composing on screen.

There is only one other very important thing to notice in this example:

public void resize(int width, int height) {

   batch.dispose();

   batch = new SpriteBatch();

   String resolution = Integer.toString(width) + "," + Integer.toString(height);

   Gdx.app.log("MJF", "Resolution changed " + resolution);

}

 

In the resize() method we dispose of and recreate our SpriteBatch().  This is because when you change the orientation of the devices from landscape to portrait or vice versa you invalidate the sprite batch, it is now the wrong size for your device.  Therefore in the resize() call, we recreate the SpriteBatch structure.

Programming


24. October 2013

 

In the previous tutorial we looked at handling mouse and keyboard events, both event driven and polled.  Now we will look at how touch works.  To follow along at this point you need to have a touch enabled device ( multi-touch with a mouse is tricky to say the least! ) although all the code will work in Desktop and HTML targets, you simply wont be able to test it.  Let’s jump right in with an example.  This example shows how to handle multiple simultaneous touches:

 

Multitouch

 

package com.gamefromscratch;

import java.util.HashMap;
import java.util.Map;

import com.badlogic.gdx.ApplicationListener;
import com.badlogic.gdx.Gdx;
import com.badlogic.gdx.InputProcessor;
import com.badlogic.gdx.graphics.Color;
import com.badlogic.gdx.graphics.GL10;
import com.badlogic.gdx.graphics.g2d.BitmapFont;
import com.badlogic.gdx.graphics.g2d.BitmapFont.TextBounds;
import com.badlogic.gdx.graphics.g2d.SpriteBatch;

public class InputDemo2 implements ApplicationListener, InputProcessor {
    private SpriteBatch batch;
    private BitmapFont font;
    private String message = "Touch something already!";
    private int w,h;
    
    class TouchInfo {
        public float touchX = 0;
        public float touchY = 0;
        public boolean touched = false;
    }
    
    private Map<Integer,TouchInfo> touches = new HashMap<Integer,TouchInfo>();
    
    @Override
    public void create() {        
        batch = new SpriteBatch();    
        font = new BitmapFont(Gdx.files.internal("data/arial-15.fnt"),false);
        font.setColor(Color.RED);
        w = Gdx.graphics.getWidth();
        h = Gdx.graphics.getHeight();
        Gdx.input.setInputProcessor(this);
        for(int i = 0; i < 5; i++){
            touches.put(i, new TouchInfo());
        }
    }

    @Override
    public void dispose() {
        batch.dispose();
        font.dispose();
    }

    @Override
    public void render() {        
        Gdx.gl.glClearColor(1, 1, 1, 1);
        Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT);
        
        batch.begin();
        
        message = "";
        for(int i = 0; i < 5; i++){
            if(touches.get(i).touched)
                message += "Finger:" + Integer.toString(i) + "touch at:" +
                        Float.toString(touches.get(i).touchX) +
                        "," +
                        Float.toString(touches.get(i).touchY) +
                        "\n";
                                
        }
        TextBounds tb = font.getBounds(message);
        float x = w/2 - tb.width/2;
        float y = h/2 + tb.height/2;
        font.drawMultiLine(batch, message, x, y);
        
        batch.end();
    }

    @Override
    public void resize(int width, int height) {
    }

    @Override
    public void pause() {
    }

    @Override
    public void resume() {
    }

    @Override
    public boolean keyDown(int keycode) {
        // TODO Auto-generated method stub
        return false;
    }

    @Override
    public boolean keyUp(int keycode) {
        // TODO Auto-generated method stub
        return false;
    }

    @Override
    public boolean keyTyped(char character) {
        // TODO Auto-generated method stub
        return false;
    }

    @Override
    public boolean touchDown(int screenX, int screenY, int pointer, int button) {
        if(pointer < 5){
            touches.get(pointer).touchX = screenX;
            touches.get(pointer).touchY = screenY;
            touches.get(pointer).touched = true;
        }
        return true;
    }

    @Override
    public boolean touchUp(int screenX, int screenY, int pointer, int button) {
        if(pointer < 5){
            touches.get(pointer).touchX = 0;
            touches.get(pointer).touchY = 0;
            touches.get(pointer).touched = false;
        }
        return true;
    }

    @Override
    public boolean touchDragged(int screenX, int screenY, int pointer) {
        // TODO Auto-generated method stub
        return false;
    }

    @Override
    public boolean mouseMoved(int screenX, int screenY) {
        // TODO Auto-generated method stub
        return false;
    }

    @Override
    public boolean scrolled(int amount) {
        // TODO Auto-generated method stub
        return false;
    }
}

Now when you run it, diagnostic information will be displayed for each finger you are touching with:

photo

 

For each finger it displays the coordinates the finger is touched up, up to a total of 5 fingers. 

So what exactly is going on here?  We create a simple class TouchInfo for holding touch details: if its touched, the X and Y coordinates.  We then create a HashMap of touches with an Integer as the key and a TouchInfo class as the data.  The key will be the index of the finger touching with.  The logic is actually in the touchDown and touchUp event handlers.  On touch down we update the touches map at the index represented by the value pointer.  As you may recall from the previous tutorial the value pointer represents which finger is currently pressed.  When the finger is released, touchUp is fired and we simply clear the touch entry at that location.  Finally in render() we loop through the touches map and display the ones that are touched and where.

At the end of the day, touches is basically identical to mouse clicks, except you can have multiple of them and there are no buttons.  Oh I suppose I should mention that the 5 touch limit in this example was just an number I picked arbitrarily.  LibGDX supports up to 20 touches although no devices do.  The iPad for example can track up to 11, the iPhone tracks up to 5, while the HTC One tracks 10.  On your Google phone you can track how many touches it supports using this app.  That said, 5 is a pretty safe and reasonable number… heck, I dont think I’ve ever used more than 4 on any device.

 

Touch gestures

 

There are a number of common gestures that have become ubiquitous in the mobile world.  Things like pinch to zoom, or flick/fling and long press have become the norm.  Fortunately GDX supports all of these things out of the box.  Let’s jump right into a simple demo:

package com.gamefromscratch;


import com.badlogic.gdx.ApplicationListener;
import com.badlogic.gdx.Gdx;
import com.badlogic.gdx.graphics.Color;
import com.badlogic.gdx.graphics.GL10;
import com.badlogic.gdx.graphics.g2d.BitmapFont;
import com.badlogic.gdx.graphics.g2d.BitmapFont.TextBounds;
import com.badlogic.gdx.graphics.g2d.SpriteBatch;
import com.badlogic.gdx.input.GestureDetector;
import com.badlogic.gdx.input.GestureDetector.GestureListener;
import com.badlogic.gdx.math.Vector2;

public class InputDemo3 implements ApplicationListener, GestureListener {
    private SpriteBatch batch;
    private BitmapFont font;
    private String message = "No gesture performed yet";
    private int w,h;

    
    @Override
    public void create() {        
        batch = new SpriteBatch();    
        font = new BitmapFont(Gdx.files.internal("data/arial-15.fnt"),false);
        font.setColor(Color.RED);
        w = Gdx.graphics.getWidth();
        h = Gdx.graphics.getHeight();
        
        GestureDetector gd = new GestureDetector(this);
        Gdx.input.setInputProcessor(gd);
    }

    @Override
    public void dispose() {
        batch.dispose();
        font.dispose();
    }

    @Override
    public void render() {        
        Gdx.gl.glClearColor(1, 1, 1, 1);
        Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT);
        
        batch.begin();
        
        TextBounds tb = font.getBounds(message);
        float x = w/2 - tb.width/2;
        float y = h/2 + tb.height/2;
        
        font.drawMultiLine(batch, message, x, y);
        
        batch.end();
    }

    @Override
    public void resize(int width, int height) {
    }

    @Override
    public void pause() {
    }

    @Override
    public void resume() {
    }

    @Override
    public boolean touchDown(float x, float y, int pointer, int button) {
        // TODO Auto-generated method stub
        return true;
    }

    @Override
    public boolean tap(float x, float y, int count, int button) {
        message = "Tap performed, finger" + Integer.toString(button);
        return true;
    }

    @Override
    public boolean longPress(float x, float y) {
        message = "Long press performed";
        return true;
    }

    @Override
    public boolean fling(float velocityX, float velocityY, int button) {
        message = "Fling performed, velocity:" + Float.toString(velocityX) +
                "," + Float.toString(velocityY);
        return true;
    }

    @Override
    public boolean pan(float x, float y, float deltaX, float deltaY) {
        message = "Pan performed, delta:" + Float.toString(deltaX) +
                "," + Float.toString(deltaY);
        return true;
    }

    @Override
    public boolean zoom(float initialDistance, float distance) {
        message = "Zoom performed, initial Distance:" + Float.toString(initialDistance) +
                " Distance: " + Float.toString(distance);
        return true;
    }

    @Override
    public boolean pinch(Vector2 initialPointer1, Vector2 initialPointer2,
            Vector2 pointer1, Vector2 pointer2) {
        message = "Pinch performed";
        return true;
    }

}

 

If you run it, as you perform various gestures they will be displayed centered on the screen.  Supported gestures include tap, fling(flick), pinch ( two fingers moving closer together ), zoom ( two fingers moving apart ), pan ( one finger hold and slide ) and long press ( tap and hold ) as well as good ole fashion touch.

Just like we implemented InputProcessor to handle touch, mouse and keyboard events, we implement the GestureListener to accept gesture events from LibGDX.  In create() you create a GestureDetector using your GestureListener and once again you register it using Gdx.input.setInputProcessor().  Each different gesture triggers the corresponding even in your GestureListener.  In each, we simple update the displayed message to reflect the most recently performed event.

One important concept we didn’t cover here is configuring your GestureDetector…  how do you determine how long a long touch is, or how long must elapse before a drag becomes a flick?  The simple answer is, using the GestureDetector constructor.  You can read more about it here.

 

Handling multiple InputProcessors

 

So, what if you wanted to handle gestures AND keyboard events… what then?  Fortunately the answer is quite simple, instead of passing setInputProcessor an InputProcessor or GestureDetector, you instead pass in an InputMultiplexer.  Like so:

package com.gamefromscratch;


import com.badlogic.gdx.ApplicationListener;
import com.badlogic.gdx.Gdx;
import com.badlogic.gdx.InputMultiplexer;
import com.badlogic.gdx.graphics.Color;
import com.badlogic.gdx.graphics.GL10;
import com.badlogic.gdx.graphics.g2d.BitmapFont;
import com.badlogic.gdx.graphics.g2d.BitmapFont.TextBounds;
import com.badlogic.gdx.graphics.g2d.SpriteBatch;
import com.badlogic.gdx.input.GestureDetector;
import com.badlogic.gdx.input.GestureDetector.GestureListener;
import com.badlogic.gdx.InputProcessor;
import com.badlogic.gdx.math.Vector2;

public class InputDemo4 implements ApplicationListener, GestureListener, InputProcessor {
    private SpriteBatch batch;
    private BitmapFont font;
    private String message = "No gesture performed yet";
    private int w,h;

    
    @Override
    public void create() {        
        batch = new SpriteBatch();    
        font = new BitmapFont(Gdx.files.internal("data/arial-15.fnt"),false);
        font.setColor(Color.RED);
        w = Gdx.graphics.getWidth();
        h = Gdx.graphics.getHeight();
        
        InputMultiplexer im = new InputMultiplexer();
        GestureDetector gd = new GestureDetector(this);
        im.addProcessor(gd);
        im.addProcessor(this);
        
        
        Gdx.input.setInputProcessor(im);
    }

    @Override
    public void dispose() {
        batch.dispose();
        font.dispose();
    }

    @Override
    public void render() {        
        Gdx.gl.glClearColor(1, 1, 1, 1);
        Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT);
        
        batch.begin();
        
        TextBounds tb = font.getBounds(message);
        float x = w/2 - tb.width/2;
        float y = h/2 + tb.height/2;
        
        font.drawMultiLine(batch, message, x, y);
        
        batch.end();
    }

    @Override
    public void resize(int width, int height) {
    }

    @Override
    public void pause() {
    }

    @Override
    public void resume() {
    }

    @Override
    public boolean touchDown(float x, float y, int pointer, int button) {
        message = "Touch down!";
        Gdx.app.log("INFO", message);
        return true;
    }

    @Override
    public boolean tap(float x, float y, int count, int button) {
        message = "Tap performed, finger" + Integer.toString(button);
        Gdx.app.log("INFO", message);
        return false;
    }

    @Override
    public boolean longPress(float x, float y) {
        message = "Long press performed";
        Gdx.app.log("INFO", message);
        return true;
    }

    @Override
    public boolean fling(float velocityX, float velocityY, int button) {
        message = "Fling performed, velocity:" + Float.toString(velocityX) +
                "," + Float.toString(velocityY);
        Gdx.app.log("INFO", message);
        return true;
    }

    @Override
    public boolean pan(float x, float y, float deltaX, float deltaY) {
        message = "Pan performed, delta:" + Float.toString(deltaX) +
                "," + Float.toString(deltaY);
        Gdx.app.log("INFO", message);
        return true;
    }

    @Override
    public boolean zoom(float initialDistance, float distance) {
        message = "Zoom performed, initial Distance:" + Float.toString(initialDistance) +
                " Distance: " + Float.toString(distance);
        Gdx.app.log("INFO", message);
        return true;
    }

    @Override
    public boolean pinch(Vector2 initialPointer1, Vector2 initialPointer2,
            Vector2 pointer1, Vector2 pointer2) {
        message = "Pinch performed";
        Gdx.app.log("INFO", message);

        return true;
    }

    @Override
    public boolean keyDown(int keycode) {
        message = "Key Down";
        Gdx.app.log("INFO", message);
        return true;
    }

    @Override
    public boolean keyUp(int keycode) {
        message = "Key up";
        Gdx.app.log("INFO", message);
        return true;
    }

    @Override
    public boolean keyTyped(char character) {
        message = "Key typed";
        Gdx.app.log("INFO", message);
        return true;
    }

    @Override
    public boolean touchDown(int screenX, int screenY, int pointer, int button) {
        message = "Touch Down";
        Gdx.app.log("INFO", message);

        return false;
    }

    @Override
    public boolean touchUp(int screenX, int screenY, int pointer, int button) {
        message = "Touch up";
        Gdx.app.log("INFO", message);
        return false;
    }

    @Override
    public boolean touchDragged(int screenX, int screenY, int pointer) {
        message = "Touch Dragged";
        Gdx.app.log("INFO", message);
        return false;
    }

    @Override
    public boolean mouseMoved(int screenX, int screenY) {
        message = "Mouse moved";
        Gdx.app.log("INFO", message);
        return false;
    }

    @Override
    public boolean scrolled(int amount) {
        message = "Scrolled";
        Gdx.app.log("INFO", message);
        return false;
    }

}

Do to the fact multiple events can be fired off at once, in addition to printing them on screen, we also log them using Gdx.app.log().  You can see logged events in the LogCat window in Eclipse:

image

There is also a program called ddms ( its a BAT script on windows ) in the android-sdk tools folder that will display the same information.

image

 

So, that’s what log() does… now back to the code.  The key part here is:

InputMultiplexer im = new InputMultiplexer();
GestureDetector gd = new GestureDetector(this);
im.addProcessor(gd);
im.addProcessor(this);

Gdx.input.setInputProcessor(im);

Essentially you create the multiplexer, then add both the InputProcessor and the GestureDetector to it via addProcessor(), then it is the multiplexer that is passed to setInputProcessor().  Otherwise the code works pretty much exactly the same.  There is two things of critical importance here.  First, the order that processors are added to the multiplexor seems to determine the order that they will have first crack at events that occurred.  Next, and this one is super important, in event handlers if you return true that means that the event is handled.  Think about that for a second, its an important concept to grasp.  While something like a touch up or down event is pretty straight forward, a say… pinch event is not.   In fact, a pinch event is composed of a number of other events, including multiple touch events.  However if you return true out of say, the touchDown event, that event will not bubble through to the gesture detector.  Therefore if you are supporting multi touch, be sure to return false from the more atomic events such as touchDown and TouchUp, so they still get a crack at handling those events!

Programming


15. October 2013

 

In this part we are going to look at how you handle mouse and keyboard input in LibGDX.  There are two ways to go about handling input, by polling for it ( as in… “Has anything happened yet? No, ok…  What about now? No, ok… Now?  Yes!  Handle it” ) or by handling events ( “Hey, you, I’v got this event for you!” ).  Which you go with generally depends on the way you structure your code.  Polling tends to be a bit more resource intensive but at the end of the day that is mostly a non-factor.

 

Polling the keyboard for input

 

Let’s jump right in and look at how you poll the keyboard for input.  Here is the code:

package input.gamefromscratch.com;

import com.badlogic.gdx.ApplicationListener;
import com.badlogic.gdx.Gdx;
import com.badlogic.gdx.Input;
import com.badlogic.gdx.graphics.GL10;
import com.badlogic.gdx.graphics.Texture;
import com.badlogic.gdx.graphics.g2d.Sprite;
import com.badlogic.gdx.graphics.g2d.SpriteBatch;

public class InputDemo implements ApplicationListener {
    private SpriteBatch batch;
    private Texture texture;
    private Sprite sprite;
    
    @Override
    public void create() {        
        float w = Gdx.graphics.getWidth();
        float h = Gdx.graphics.getHeight();
        batch = new SpriteBatch();
        
        texture = new Texture(Gdx.files.internal("data/0001.png"));
        sprite = new Sprite(texture);
        sprite.setPosition(w/2 -sprite.getWidth()/2, h/2 - sprite.getHeight()/2);
    }

    @Override
    public void dispose() {
        batch.dispose();
        texture.dispose();
    }

    @Override
    public void render() {        
        Gdx.gl.glClearColor(1, 1, 1, 1);
        Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT);
        
        if(Gdx.input.isKeyPressed(Input.Keys.LEFT)){
            if(Gdx.input.isKeyPressed(Input.Keys.CONTROL_LEFT))
                sprite.translateX(-1f);
            else
                sprite.translateX(-10.0f);
        }
        if(Gdx.input.isKeyPressed(Input.Keys.RIGHT)){
            if(Gdx.input.isKeyPressed(Input.Keys.CONTROL_LEFT))
                sprite.translateX(1f);
            else
                sprite.translateX(10.0f);
        }
        batch.begin();
        sprite.draw(batch);
        batch.end();
    }

    @Override
    public void resize(int width, int height) {
    }

    @Override
    public void pause() {
    }

    @Override
    public void resume() {
    }
}

 

Other than the highlighted bit and the translateX method, everything here we have seen before.  Basically we draw a simple sprite centered to the screen and each frame we check to see if the user has pressed the LEFT or RIGHT arrow.  If they have, we check if they also have the left control key held.  If so, we move slowly to the left or right.  If they don’t have Control pressed, we move instead by 10 pixels.

 

Here is the app, you need to click it first to give it keyboard focus:

 

If it doesn’t work in an frame, click here.

Just use the left and right arrows to move the jet. Hold down control to move slowly.  There is no clipping so the sprite can fly way off screen.

 

In terms of what the new code is doing, the Sprite.translateX method is pretty self explanatory.  It moves the sprite by a certain amount of pixels along the X axis.  There is a translateY method as well, as well as a more general translate method.  The key method in this example is isKeyPressed() member function of the input instance of the global Gdx object.  We used a similar instance member when we accessed Gdx.files.  These are public static references to the various sub-systems GDX depends on, you can read more here.  isKeyPressed is passed a Key value defined in the Keys object and returns true if that key is currently pressed.  As you can see when we later tested if the Control key is also pressed, multiple keys can be pressed at the same time.

 

Polling the Mouse for input

 

Now let’s take a look at how you poll the mouse for input.  To save space, this code is identical to the last example, with only the render() method replaced.

public void render() {        
    Gdx.gl.glClearColor(1, 1, 1, 1);
    Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT);
    
    if(Gdx.input.isButtonPressed(Input.Buttons.LEFT)){
        sprite.setPosition(Gdx.input.getX() - sprite.getWidth()/2,
                Gdx.graphics.getHeight() - Gdx.input.getY() - sprite.getHeight()/2);
    }
    if(Gdx.input.isButtonPressed(Input.Buttons.RIGHT)){
        sprite.setPosition(Gdx.graphics.getWidth()/2 -sprite.getWidth()/2, 
                Gdx.graphics.getHeight()/2 - sprite.getHeight()/2);
    }
    batch.begin();
    sprite.draw(batch);
    batch.end();
}

 

Here we instead are checking if a mouse button has been pressed using isButtonPressed passing in a button value defined in the Buttons object.  If the left button is pressed, get then poll the mouse position using Gdx.input.getX() and Gdx.input.getY() and set the sprites location to that position.  The math may look a bit overly complicated, why didn’t we simply set the location to the values returned by getX/Y?  There are two reasons.  First, our sprites coordinate is relative to it’s bottom left corner. so if we want to center the sprite, we need to take half the sprites width and height into consideration.  The next complication comes from the fact that LibGDX sets the origin at the bottom left corner, but mouse positions are relative to the top left corner.  Simply subtracting the position from the screen height gives you the location of the mouse in screen coordinates.  We also check to see if the user as hit the right mouse button, and if they have we reposition the jet sprite at the center of the window.

 

If it doesn’t work in an frame, click here.

Once again, you need to click within above before it will start receiving mouse events ( depending on your browser ).  Left click and the sprite should move to the location you clicked.  Right click to return to default ( in theory… ), right click behaviour is a bit random in web browsers.

 

Event driven keyboard and mouse handling

 

Now we will look at handling the functionality of both of the above examples ( as a single example ), but this time using an event driven approach.

package input.gamefromscratch.com;

import com.badlogic.gdx.ApplicationListener;
import com.badlogic.gdx.Gdx;
import com.badlogic.gdx.Input.Buttons;
import com.badlogic.gdx.Input.Keys;
import com.badlogic.gdx.InputProcessor;
import com.badlogic.gdx.graphics.GL10;
import com.badlogic.gdx.graphics.Texture;
import com.badlogic.gdx.graphics.g2d.Sprite;
import com.badlogic.gdx.graphics.g2d.SpriteBatch;

public class InputDemo implements ApplicationListener, InputProcessor {
    private SpriteBatch batch;
    private Texture texture;
    private Sprite sprite;
    private float posX, posY;
    
    @Override
    public void create() {        
        float w = Gdx.graphics.getWidth();
        float h = Gdx.graphics.getHeight();
        batch = new SpriteBatch();
        
        texture = new Texture(Gdx.files.internal("data/0001.png"));
        sprite = new Sprite(texture);
        posX = w/2 - sprite.getWidth()/2;
        posY = h/2 - sprite.getHeight()/2;
        sprite.setPosition(posX,posY);
        
        Gdx.input.setInputProcessor(this);
    }

    @Override
    public void dispose() {
        batch.dispose();
        texture.dispose();
    }

    @Override
    public void render() {        
        Gdx.gl.glClearColor(1, 1, 1, 1);
        Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT);

        sprite.setPosition(posX,posY);
        batch.begin();
        sprite.draw(batch);
        batch.end();
    }

    @Override
    public void resize(int width, int height) {
    }

    @Override
    public void pause() {
    }

    @Override
    public void resume() {
    }

    @Override
    public boolean keyDown(int keycode) {
        float moveAmount = 1.0f;
        if(Gdx.input.isKeyPressed(Keys.CONTROL_LEFT))
            moveAmount = 10.0f;
        
        if(keycode == Keys.LEFT)
            posX-=moveAmount;
        if(keycode == Keys.RIGHT)
            posX+=moveAmount;
        return true;
    }

    @Override
    public boolean keyUp(int keycode) {
        return false;
    }

    @Override
    public boolean keyTyped(char character) {
        return false;
    }

    @Override
    public boolean touchDown(int screenX, int screenY, int pointer, int button) {
        if(button == Buttons.LEFT){
            posX = screenX - sprite.getWidth()/2;
            posY = Gdx.graphics.getHeight() - screenY - sprite.getHeight()/2;
        }
        if(button == Buttons.RIGHT){
            posX = Gdx.graphics.getWidth()/2 - sprite.getWidth()/2;
            posY = Gdx.graphics.getHeight()/2 - sprite.getHeight()/2;
        }
        return false;
    }

    @Override
    public boolean touchUp(int screenX, int screenY, int pointer, int button) {
        return false;
    }

    @Override
    public boolean touchDragged(int screenX, int screenY, int pointer) {
        return false;
    }

    @Override
    public boolean mouseMoved(int screenX, int screenY) {
        return false;
    }

    @Override
    public boolean scrolled(int amount) {
        return false;
    }
}

 

And here it is running:

If it doesn’t work in an frame, click here.

 

The code is structured quite a bit differently from when we polled for input.  The most immediate thing to be aware of is our class declaration:

public class InputDemo implements ApplicationListener, InputProcessor {

 

We are implementing another interface, InputProcessor, which as you can see adds a number of overrides to our code.  The most important ones we are dealing with here are keyDown and touchDown.  Touch you say?  Yeah, LibGDX treats the mouse and touch input as the same thing.  We will look at this in a bit more detail later on.  In addition to implementing the various methods of our interface, we also need to register our InputProcessor with the global input instance, this is done here:

Gdx.input.setInputProcessor(this);

 

At this point, our various event handlers will now be called whenever an event occurs.  keyDown will be fired when a key is pressed ( while keyUp is fired when it is released, and keyTyped is fired after it has been fired and released ).  The parameter is the value of the key pressed.  Once again, these values are available in the Keys object.  One thing you may have noticed is that we still poll to see if the Control key is pressed.  The alternative would be to set a flag when the control key is pressed and clear it when it is released.  It is important to realize that a keyDown event will be fired for each individual key fired, so if you want to handle multiple simutanious key presses, this may not be the best way to approach the subject.  Another thing you might notice is that you have to hit the key multiple times to move.  This is because a key press generates only a single event ( as does it’s release ).  If you want to have the old behavior that holding down the key will move the character continously, you will need to implement the logic yourself.  Once again, this can simply be done by setting a flag in your code on keyDown and toggle it when the keyUp event is called.

 

The touchDown event on the other hand is much more straight forward.  It can be a bit confusing handling “mouse” events called “touches”, but it makes sense.  Generally the logic you handle for both would be exactly the same, so no sense treating them differently.  The parameters passed in to touchDown are the x and y coordinates of the touch/click location, the pointer and button clicked.  On a mobile device the Button value will always be Buttons.LEFT.  Once again, screen coordinates and image coordiantes arent the same, so we need to deal with that in our positioning.  Notice how I glossed over just what exactly pointer is?  Well, pointer is a bit oddly named in my opinion.  TouchIndex would probably have made more sense, especially with pointer having a pair of very well defined meanings already.  The pointer value is value between 0 and n ( defined as 20 in LibGDX, in reality much lower ) that represents the ORDER in which the touch event occurred in the event of multiple simultaneous touches.  Therefore if you have multiple fingers touching, a pointer value of 0 would indicate that this touch event represents the first finger to touch the screen, while a value of 3 would be the fourth finger to touch the screen.  Dont worry, we will talk about this later when we deal specifically with touch.

Programming


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