andengine smooth scrolling and zooming with SurfaceScrollDetector, PinchZoomDetector

Question

I'm trying to implement smooth TMX map scrolling and zooming with SurfaceScrollDetector and PinchZoomDetector.

Here is my code:

public class TMXTiledMapExample extends SimpleBaseGameActivity implements IOnSceneTouchListener, IScrollDetectorListener, IPinchZoomDetectorListener {

private static final int CAMERA_WIDTH = 480;
private static final int CAMERA_HEIGHT = 320;

private SmoothCamera camera;

private TMXTiledMap mTMXTiledMap;

private SurfaceScrollDetector mScrollDetector;
private PinchZoomDetector mPinchZoomDetector;
private float mPinchZoomStartedCameraZoomFactor;

@Override
public EngineOptions onCreateEngineOptions() {
    this.camera = new SmoothCamera(0, 0, CAMERA_WIDTH, CAMERA_HEIGHT, 400, 400, 10f);
    final CroppedResolutionPolicy canvasSurface = new CroppedResolutionPolicy(CAMERA_WIDTH, CAMERA_HEIGHT);
    EngineOptions engineOptions = new EngineOptions(true, ScreenOrientation.LANDSCAPE_FIXED, canvasSurface, this.camera);

    if (MultiTouch.isSupported(this)) {
        if (MultiTouch.isSupportedDistinct(this)) {
            Toast.makeText(this, "MultiTouch detected --> Both controls will work properly!", Toast.LENGTH_SHORT).show();
        } else {
            Toast.makeText(this, "MultiTouch detected, but your device has problems distinguishing between fingers.\n\nControls are placed at different vertical locations.", Toast.LENGTH_LONG)
                    .show();
        }
    } else {
        Toast.makeText(this, "Sorry your device does NOT support MultiTouch!\n\n(Falling back to SingleTouch.)\n\nControls are placed at different vertical locations.", Toast.LENGTH_LONG).show();
    }

    return engineOptions;
}

@Override
public void onCreateResources() {
    BitmapTextureAtlasTextureRegionFactory.setAssetBasePath("gfx/");
}

@Override
public Scene onCreateScene() {
    this.mEngine.registerUpdateHandler(new FPSLogger());

    final Scene scene = new Scene();
    scene.setOnAreaTouchTraversalFrontToBack();

    this.mScrollDetector = new SurfaceScrollDetector(this);
    this.mPinchZoomDetector = new PinchZoomDetector(this);

    scene.setOnSceneTouchListener(this);
    scene.setTouchAreaBindingOnActionDownEnabled(true);

    try {
        final TMXLoader tmxLoader = new TMXLoader(this.getAssets(), this.mEngine.getTextureManager(), TextureOptions.BILINEAR, this.getVertexBufferObjectManager(),
                new ITMXTilePropertiesListener() {
                    @Override
                    public void onTMXTileWithPropertiesCreated(final TMXTiledMap pTMXTiledMap, final TMXLayer pTMXLayer, final TMXTile pTMXTile,
                            final TMXProperties<TMXTileProperty> pTMXTileProperties) {
                    }
                });
        this.mTMXTiledMap = tmxLoader.loadFromAsset("tmx/desert2.tmx");

    } catch (final TMXLoadException e) {
        Debug.e(e);
    }

    final TMXLayer tmxLayer = this.mTMXTiledMap.getTMXLayers().get(0);
    scene.attachChild(tmxLayer);

    this.camera.setBounds(0, 0, tmxLayer.getHeight(), tmxLayer.getWidth());
    this.camera.setBoundsEnabled(true);

    return scene;
}

@Override
public void onScrollStarted(final ScrollDetector pScollDetector, final int pPointerID, final float pDistanceX, final float pDistanceY) {
    final float zoomFactor = this.camera.getZoomFactor();
    this.camera.offsetCenter(-pDistanceX / zoomFactor, -pDistanceY / zoomFactor);
}

@Override
public void onScroll(final ScrollDetector pScollDetector, final int pPointerID, final float pDistanceX, final float pDistanceY) {
    final float zoomFactor = this.camera.getZoomFactor();
    this.camera.offsetCenter(-pDistanceX / zoomFactor, -pDistanceY / zoomFactor);
}

@Override
public void onScrollFinished(final ScrollDetector pScollDetector, final int pPointerID, final float pDistanceX, final float pDistanceY) {
    final float zoomFactor = this.camera.getZoomFactor();
    this.camera.offsetCenter(-pDistanceX / zoomFactor, -pDistanceY / zoomFactor);
}

@Override
public void onPinchZoomStarted(final PinchZoomDetector pPinchZoomDetector, final TouchEvent pTouchEvent) {
    this.mPinchZoomStartedCameraZoomFactor = this.camera.getZoomFactor();
}

@Override
public void onPinchZoom(final PinchZoomDetector pPinchZoomDetector, final TouchEvent pTouchEvent, final float pZoomFactor) {
    this.camera.setZoomFactor(this.mPinchZoomStartedCameraZoomFactor * pZoomFactor);
}

@Override
public void onPinchZoomFinished(final PinchZoomDetector pPinchZoomDetector, final TouchEvent pTouchEvent, final float pZoomFactor) {
    this.camera.setZoomFactor(this.mPinchZoomStartedCameraZoomFactor * pZoomFactor);
}

@Override
public boolean onSceneTouchEvent(final Scene pScene, final TouchEvent pSceneTouchEvent) {
    this.mPinchZoomDetector.onTouchEvent(pSceneTouchEvent);

    if (this.mPinchZoomDetector.isZooming()) {
        this.mScrollDetector.setEnabled(false);
    } else {
        if (pSceneTouchEvent.isActionDown()) {
            this.mScrollDetector.setEnabled(true);
        }
        this.mScrollDetector.onTouchEvent(pSceneTouchEvent);
    }

    return true;
}
}

Scrolling and zooming in this code are not very smooth. Where is the issue with it ? How to create nice, inertial scrolling ?

One more question for zooming. How it could be restricted with min and max zoomfactor ? Should I place a special conditions into the IPinchZoomDetectorListener methods or it could be achived with some parameters provided to my camera object ?

Also, what is a "normal" values for the three last SmoothCamera parameters - final float pMaxVelocityX, final float pMaxVelocityY, final float pMaxZoomFactorChange ?

Answer 1

I have done similar type of work before so I can help you in achieving your objective.

First of all if you want zoom in/out functionality then you have to use ZoomCamera in which you have to only give width and height, all other parameters are used by default value.

    mZoomCamera = new ZoomCamera(0, 0, Constants.CAMERA_WIDTH,
            Constants.CAMERA_HEIGHT);
    mZoomCamera.setBounds(0f, 0f, Constants.CAMERA_WIDTH,
            Constants.CAMERA_HEIGHT);
    mZoomCamera.setBoundsEnabled(true);

In the example code, you see how I set bounds for camera so there is no chance camera can go out of this. And also I thing you get abnormal behaviour because of inappropriate velocity you are providing.

For for setting specific zoom value you can use following code,

private void setCameraZoomFactor(float pZoomFactor) {
    newZoomFactor = mPinchZoomStartedCameraZoomFactor * pZoomFactor;
    if (newZoomFactor < 1f)
        newZoomFactor = 1f;
    if (newZoomFactor > 1.5f)
        newZoomFactor = 1.5f;

    mZoomCamera.setZoomFactor(newZoomFactor);
}

You have to call this method in your onPinchZoom method.

I think now I have given answer of your all of the questions.