Android使用Rotate3dAnimation实现3D旋转动画效果的实例代码

利用Android的ApiDemos的Rotate3dAnimation实现了个图片3D旋转的动画，围绕Y轴进行旋转，还可以实现Z轴的缩放。点击开始按钮开始旋转，点击结束按钮停止旋转。

代码如下：:

Rotate3dAnimation.java

public class Rotate3dAnimation extends Animation {  private final float mFromDegrees;  private final float mToDegrees;  private final float mCenterX;  private final float mCenterY;  private final float mDepthZ;  private final boolean mReverse;  private Camera mCamera;  /**  * Creates a new 3D rotation on the Y axis. The rotation is defined by its  * start angle and its end angle. Both angles are in degrees. The rotation  * is performed around a center point on the 2D space, definied by a pair  * of X and Y coordinates, called centerX and centerY. When the animation  * starts, a translation on the Z axis (depth) is performed. The length  * of the translation can be specified, as well as whether the translation  * should be reversed in time.  *  * @param fromDegrees the start angle of the 3D rotation  * @param toDegrees the end angle of the 3D rotation  * @param centerX the X center of the 3D rotation  * @param centerY the Y center of the 3D rotation  * @param reverse true if the translation should be reversed, false otherwise  */  public Rotate3dAnimation(float fromDegrees, float toDegrees,  float centerX, float centerY, float depthZ, boolean reverse) {  mFromDegrees = fromDegrees;  mToDegrees = toDegrees;  mCenterX = centerX;  mCenterY = centerY;  mDepthZ = depthZ;  mReverse = reverse;  }  @Override  public void initialize(int width, int height, int parentWidth, int parentHeight) {  super.initialize(width, height, parentWidth, parentHeight);  mCamera = new Camera();  }  @Override  protected void applyTransformation(float interpolatedTime, Transformation t) {  final float fromDegrees = mFromDegrees;  float degrees = fromDegrees + ((mToDegrees - fromDegrees) * interpolatedTime);  final float centerX = mCenterX;  final float centerY = mCenterY;  final Camera camera = mCamera;  final Matrix matrix = t.getMatrix();  //保存一次camera初始状态，用于restore()  camera.save();  if (mReverse) {  camera.translate(0.0f, 0.0f, mDepthZ * interpolatedTime);  } else {  camera.translate(0.0f, 0.0f, mDepthZ * (1.0f - interpolatedTime));  }  //围绕Y轴旋转degrees度  camera.rotateY(degrees);  //行camera中取出矩阵，赋值给matrix  camera.getMatrix(matrix);  //camera恢复到初始状态，继续用于下次的计算  camera.restore();  matrix.preTranslate(-centerX, -centerY);  matrix.postTranslate(centerX, centerY);  } }

Test3DRotateActivity.java

public class Test3DRotateActivity extends Activity {  /** Called when the activity is first created. */  private final String TAG="Test3DRotateActivity";  private ImageView image;  private Button start ,stop;  private Rotate3dAnimation rotation;  private StartNextRotate startNext;  @Override  public void onCreate(Bundle savedInstanceState) {  super.onCreate(savedInstanceState);  setContentView(R.layout.main);  image = (ImageView) findViewById(R.id.image);  start=(Button) findViewById(R.id.start);  stop = (Button) findViewById(R.id.stop);  start.setOnClickListener(new OnClickListener() {  public void onClick(View v) {  // TODO Auto-generated method stub  //进行360度的旋转  startRotation(0,360);  }  });  stop.setOnClickListener(new OnClickListener() {  public void onClick(View v) {  // TODO Auto-generated method stub  image.clearAnimation();  }  });  }  private void startRotation(float start, float end) {  // 计算中心点  final float centerX = image.getWidth() / 2.0f;  final float centerY = image.getHeight() / 2.0f;  Log.d(TAG, "centerX="+centerX+", centerY="+centerY);  // Create a new 3D rotation with the supplied parameter  // The animation listener is used to trigger the next animation  //final Rotate3dAnimation rotation =new Rotate3dAnimation(start, end, centerX, centerY, 310.0f, true);  //Z轴的缩放为0  rotation =new Rotate3dAnimation(start, end, centerX, centerY, 0f, true);  rotation.setDuration(2000);  rotation.setFillAfter(true);  //rotation.setInterpolator(new AccelerateInterpolator());  //匀速旋转  rotation.setInterpolator(new LinearInterpolator());  //设置监听  startNext = new StartNextRotate();  rotation.setAnimationListener(startNext);  image.startAnimation(rotation);  }  private class StartNextRotate implements AnimationListener{  public void onAnimationEnd(Animation animation) {  // TODO Auto-generated method stub  Log.d(TAG, "onAnimationEnd......");  image.startAnimation(rotation);  }  public void onAnimationRepeat(Animation animation) {  // TODO Auto-generated method stub  }  public void onAnimationStart(Animation animation) {  // TODO Auto-generated method stub  }  } }

main.xml

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

代码中用Camera来实现动画，Camera就是一个摄像机，一个物体原地不动，我们带着摄像机按设定的角度进行移动，之后从Camera中取出完成该动画的Matrix，然后画我们的物体，这个就是这个3D动画实现的原理。
具体的解释见代码中注释部分，重点说一下Rotate3dAnimation.java中的

matrix.preTranslate(-centerX, -centerY); matrix.postTranslate(centerX, centerY);

由于旋转是以(0,0)为中心的,所以为了把界面的中心与(0,0)对齐,就要preTranslate(-centerX, -centerY),旋转完成后,调用postTranslate(centerX, centerY),再把图片移回来,这样看到的动画效果就是activity的界面图片从在centerX为中心绕Y轴旋转了。
你还可以把上面代码改成

matrix.preTranslate(-centerX, 0); matrix.postTranslate(centerX, 0);

看有什么不同效果。

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