Android(安卓)3D旋转动画实现

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 stubimage.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 stubLog.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"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="fill_parent"    android:layout_height="fill_parent"    android:orientation="vertical" >    <Button         android:id="@+id/start"        android:layout_width="wrap_content"android:layout_height="wrap_content"android:text="开始"        />    <Button         android:id="@+id/stop"        android:layout_width="wrap_content"android:layout_height="wrap_content"android:text="结束"        />    <ImageView         android:id="@+id/image"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:src="@drawable/t1"                /></LinearLayout>

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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