SmoothScrollDetector

[bigpete591]

Here is a class you can use to allow smooth scrolling of your scenes.

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Using java Syntax Highlighting

1. package org.andengine.input.touch.detector;
2.  
3. import org.andengine.engine.camera.ZoomCamera;
4. import org.andengine.engine.handler.IUpdateHandler;
5. import org.andengine.entity.scene.Scene;
6.  
7. public class SmoothScrollDetector extends SurfaceScrollDetector {
8.  
9.         private static class ScrollListener implements IScrollDetectorListener {
10.  
11.                 @Override
12.                 public void onScrollStarted(ScrollDetector pScollDetector,
13.                                 int pPointerID, float pDistanceX, float pDistanceY) {
14.                         SmoothScrollDetector smoothScrollDetector = (SmoothScrollDetector) pScollDetector;
15.  
16.                         smoothScrollDetector.mScrollAmountX += pDistanceX;
17.                         smoothScrollDetector.mScrollAmountY += pDistanceY;
18.                 }
19.  
20.                 @Override
21.                 public void onScroll(ScrollDetector pScollDetector, int pPointerID,
22.                                 float pDistanceX, float pDistanceY) {
23.                         SmoothScrollDetector smoothScrollDetector = (SmoothScrollDetector) pScollDetector;
24.  
25.                         smoothScrollDetector.mScrollAmountX += pDistanceX;
26.                         smoothScrollDetector.mScrollAmountY += pDistanceY;
27.                 }
28.  
29.                 @Override
30.                 public void onScrollFinished(ScrollDetector pScollDetector,
31.                                 int pPointerID, float pDistanceX, float pDistanceY) {
32.                         SmoothScrollDetector smoothScrollDetector = (SmoothScrollDetector) pScollDetector;
33.  
34.                         smoothScrollDetector.mScrollAmountX += pDistanceX;
35.                         smoothScrollDetector.mScrollAmountY += pDistanceY;
36.                 }
37.  
38.         }
39.  
40.         private final class ScrollUpdater implements IUpdateHandler {
41.                 @Override
42.                 public void onUpdate(float pSecondsElapsed) {
43.                         if (mScrollAmountX == 0 && mScrollAmountY == 0)
44.                                 return;
45.  
46.                         final float zoomFactor = mCamera.getZoomFactor();
47.  
48.                         float xScroll = mScrollAmountX * (pSecondsElapsed * mScrollSpeed);
49.                         float yScroll = mScrollAmountY * (pSecondsElapsed * mScrollSpeed);
50.  
51.                         if (Math.abs(xScroll) > Math.abs(mScrollAmountX))
52.                                 xScroll = mScrollAmountX;
53.                         if (Math.abs(yScroll) > Math.abs(mScrollAmountY))
54.                                 yScroll = mScrollAmountY;
55.  
56.                         mCamera.offsetCenter(-xScroll / zoomFactor, -yScroll / zoomFactor);
57.  
58.                         mScrollAmountX -= xScroll;
59.                         mScrollAmountY -= yScroll;
60.  
61.                         if (Math.abs(mScrollAmountX) < 1)
62.                                 mScrollAmountX = 0;
63.                         if (Math.abs(mScrollAmountY) < 1)
64.                                 mScrollAmountY = 0;
65.                 }
66.  
67.                 @Override
68.                 public void reset() {
69.  
70.                 }
71.         }
72.  
73.         private static final float TRIGGER_SCROLL_MINIMUM_DISTANCE_DEFAULT = 10;
74.         private static final float SCROLL_SPEED_DEFAULT = 12;
75.  
76.         private ZoomCamera mCamera;
77.         private Scene mScene;
78.         private float mScrollSpeed;
79.  
80.         public float mScrollAmountX = 0;
81.         public float mScrollAmountY = 0;
82.         private ScrollUpdater mUpdateHandler;
83.  
84.         public SmoothScrollDetector(ZoomCamera camera, Scene scene) {
85.                 this(SmoothScrollDetector.TRIGGER_SCROLL_MINIMUM_DISTANCE_DEFAULT,
86.                                 camera, scene, SmoothScrollDetector.SCROLL_SPEED_DEFAULT);
87.         }
88.  
89.         public SmoothScrollDetector(float pTriggerScrollMinimumDistance,
90.                         ZoomCamera camera, Scene scene, float scrollSpeed) {
91.                 super(pTriggerScrollMinimumDistance, new ScrollListener());
92.                 mCamera = camera;
93.                 mScene = scene;
94.                 mScrollSpeed = scrollSpeed;
95.  
96.                 mUpdateHandler = new ScrollUpdater();
97.                 this.enable();
98.         }
99.  
100.         public void disable() {
101.                 mScene.unregisterUpdateHandler(mUpdateHandler);
102.         }
103.  
104.         public void enable() {
105.                 mScene.registerUpdateHandler(mUpdateHandler);
106.         }
107.  
108. }
109.  

Parsed in 0.043 seconds, using GeSHi 1.0.8.4

To use it, create a new SmoothScrollDetector object, and pass it the reference to your camera and scene. Then pass the scene touch events to your scroll detector:

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Syntax: [ Download ] [ Show ]

Using java Syntax Highlighting

1.         @Override
2.         public boolean onSceneTouchEvent(final Scene pScene, final TouchEvent pSceneTouchEvent) {
3.                 this.mScrollDetector.onTouchEvent(pSceneTouchEvent);
4.                 return true;
5.         }      
6.  

Parsed in 0.041 seconds, using GeSHi 1.0.8.4

[tomasz.k]

Thank you very much for this detector.

But Im a noob and when I implement this class nothing happens.

I set up SmoothCamera;

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Using java Syntax Highlighting

1. private ZoomCamera pCamera;
2. ...
3. pCamera = new ZoomCamera(0, 0, 800, 480);
4.                
5.                 return new EngineOptions(true, ScreenOrientation.LANDSCAPE_SENSOR,
6.                                 new RatioResolutionPolicy(CAM_WIDTH, CAM_HEIGHT), pCamera);
7. ...
8.  

Parsed in 0.069 seconds, using GeSHi 1.0.8.4

I load my textures and regions:

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Using java Syntax Highlighting

1. ...
2.                 bgAtlas = new BitmapTextureAtlas(getTextureManager(), 1000, 480, TextureOptions.BILINEAR);
3.                 bgRegion = BitmapTextureAtlasTextureRegionFactory.createFromAsset(
4.                                 bgAtlas, this, "scene1.png", 0, 0);
5.  
6.                 bgAtlas.load();
7.  
8.                 pOnCreateResourcesCallback.onCreateResourcesFinished();
9. ...
10.  

Parsed in 0.037 seconds, using GeSHi 1.0.8.4

I set up my scene and listeners.

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Using java Syntax Highlighting

1. pScene = new Scene();
2.                 Sprite sp = new Sprite(0, 0, bgRegion, this.getVertexBufferObjectManager());
3.                 pScene.setBackground(new SpriteBackground(sp = new Sprite(0, 0, bgRegion, this.getVertexBufferObjectManager())));
4.                 myScrollDetector = new SmoothScrollDetector(pCamera, pScene);        
5.                 pScene.setOnSceneTouchListener(myScrollDetector);
6.         pScene.setOnSceneTouchListenerBindingOnActionDownEnabled(true);
7.        
8.                 pOnCreateSceneCallback.onCreateSceneFinished(pScene);
9.  
10.  

Parsed in 0.039 seconds, using GeSHi 1.0.8.4

And nothing scrolls :/ when I for example add sprite on it, only he is scrolling. When I want to scroll my background and everything which is on it(sprite's) i must to use sprite as a background instead of pScene.setBackground(...) ?

[bigpete591]

I'm not sure about scrolling of backgrounds. Does it scroll normally if you use the standard scroll detector?

[GabS]

Thanks a lot !