实际项目中，系统提供给我们的这几个补间动画可能会无法满足我们的需求，这时我们就可以自定义补间动画。

步骤：

1. 自定义类，继承Animation
2. 复写父类initialize(int width, int height, int parentWidth, int parentHeight)方法，做一些初始化工作
3. 复写父类applyTransformation(float interpolatedTime, Transformation t)方法，进行相应的矩阵变换，涉及数学

public class MyAnimation extends Animation {

    @Override
    public void initialize(int width, int height, int parentWidth, int parentHeight) {
        super.initialize(width, height, parentWidth, parentHeight);
    }

    @Override
    protected void applyTransformation(float interpolatedTime, Transformation t) {
        super.applyTransformation(interpolatedTime, t);
    }
}

来自Android官方提供的ApiDemo中的示例：

Rotate3dAnimation 可以围绕Y 轴旋转并且同时沿着Z 轴平移从而实现一种类似于 3D的效果。

public class Rotate3dAnimation extends Animation {  

    //开始角度  
    private float startDegree;  
    //结束角度  
    private float endDegree;  

    /** 
     * 这个旋转动画围绕在2D空间的中心点执行.你可以用X轴坐标(叫做centerX)和Y轴(叫做centerY) 
     * 坐标来定义这个中心点 
     */  
    private float centerX;  
    private float centerY;  
    /** 
     * 控制镜头景深，不需要的话给0值即可 
     * mReverse 为true，表示反方向，false 表示正方向 
     */  
    private float deepZ;  
    private boolean mReverse;  
    //用于辅助实现3d效果。  
    private Camera mCamera;  

    //X轴方向，或Y轴方向  
    enum DIRECTION {  
        X, Y  
    }  

    DIRECTION direction = DIRECTION.Y;  

    Rotate3dAnimation(float fromDegree, float toDegree, float centerX,  
                      float centerY, float deepZ, boolean reverse) {  
        this.startDegree = fromDegree;  
        this.endDegree = toDegree;  
        this.centerX = centerX;  
        this.centerY = centerY;  
        this.deepZ = deepZ;  
        this.mReverse = reverse;  
    }  

    Rotate3dAnimation(float fromDegree, float toDegree, float centerX,  
                      float centerY, float deepZ, boolean reverse, DIRECTION direction) {  
        this.startDegree = fromDegree;  
        this.endDegree = toDegree;  
        this.centerX = centerX;  
        this.centerY = centerY;  
        this.deepZ = deepZ;  
        this.mReverse = reverse;  
        this.direction = direction;  
    }  

    @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) {  
        super.applyTransformation(interpolatedTime, t);  
        float fromDegree = startDegree;  
        float degree = fromDegree + (endDegree - startDegree) * interpolatedTime;  

        final Matrix matrix = t.getMatrix();  

        mCamera.save();  
        if (mReverse) {  
            mCamera.translate(0, 0, deepZ * interpolatedTime);  
        } else {  
            mCamera.translate(0, 0, deepZ * (1 - interpolatedTime));  
        }  
        if (direction == DIRECTION.Y) {  
            mCamera.rotateY(degree);  
        } else {  
            mCamera.rotateX(degree);  
        }  
        mCamera.getMatrix(matrix);  
        mCamera.restore();  

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