import android.graphics.Camera;
import android.graphics.Matrix;
import android.view.animation.Animation;
import android.view.animation.Transformation;public class Rotate3DAnimation extends Animation {// 3d rotateprivate float mFromDegrees;private float mToDegrees;private float mCenterX;private float mCenterY;private Camera mCamera;public Rotate3DAnimation(float fromDegrees, float toDegrees){mFromDegrees = fromDegrees;mToDegrees = toDegrees;}@Overridepublic void initialize(int width, int height, int parentWidth,int parentHeight){super.initialize(width, height, parentWidth, parentHeight);mCenterX = width / 2;mCenterY = height / 2;mCamera = new Camera();}@Overrideprotected void applyTransformation(float interpolatedTime, Transformation t){final float fromDegrees = mFromDegrees;float degrees = fromDegrees + (mToDegrees - mFromDegrees) * interpolatedTime;final Matrix matrix = t.getMatrix();mCamera.save();mCamera.rotateY(degrees);mCamera.getMatrix(matrix);mCamera.restore();//matrix.preTranslate(-mCenterX, -mCenterY);matrix.postTranslate(mCenterX, mCenterY);}
}

看代码，首先重载了initialize()方法，在里面初始化中间坐标mCenterX、mCenterY以及实例化Camera对象，initialize()是一个回调函数告诉Animation目标View的大小参数，在这里可以初始化一些相关的参数，例如设置动画持续时间、设置Interpolator、设置动画的参考点等。applyTransformation (float interpolatedTime, Transformation t)函数来实现自定义动画效果，在绘制动画的过程中会反复的调用applyTransformation 函数。通过参数Transformation 来获取变换的矩阵（matrix），final Matrix matrix = t.getMatrix()，通过改变矩阵就可以实现各种复杂的效果。Camera类是用来实现绕Y轴旋转后透视投影的，首先通过t.getMatrix()取得当前的矩阵，然后camera.rotateY对矩阵进行旋转。preTranslate函数是在旋转前移动而postTranslate是在旋转完成后移动，主要作用是让对象围绕自己的中心二旋转。