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;
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 {
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
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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