Android高仿寺库RecycleView的item滑动视差

寺库app的广告，最近在地铁满天飞，打开app看了看，有个页面比较炫，遂拿来模仿一番，先来简单看看
寺库实现的效果。

sicoo.gif

luffy.gif

    //doTranslate中调用getValues获取单个item和RecycleView的高度及坐标点
    private boolean getValues() {
    int[] values = getListener().requireValuesForTranslate();
    if (values == null)
        return false;
    this.rowHeight = values[0];
    this.rowYPos = values[1];
    this.recyclerViewHeight = values[2];
    this.recyclerViewYPos = values[3];
    return true;
}

private void calculateAndMove() {
    //item rowYPos距离中间点的位置
    float distanceFromCenter = (recyclerViewYPos + recyclerViewHeight) / 2 - rowYPos;
    //图片单位像素值
    int imageHeight = getDrawable().getIntrinsicHeight();
    float scale = 1;
    if (shouldCenterCrop) {
        scale = recomputeImageMatrix();
        imageHeight *= scale;
        //centerCrop之后图片的高度
    }
    //图片可以滑动的距离范围
    float difference = imageHeight - rowHeight;
    //item在recyclerView中的滚动距离
    float move = (distanceFromCenter / recyclerViewHeight) * difference * parallaxValue;
    //ImageView需要移动到位置
    float translate = (move - difference)/ 2;
    //以上两行代码，如果有能解释清楚地，欢迎评论！
    moveTo(translate, scale);
}
 /** 
  *计算scale值
  * @return
  */
private float recomputeImageMatrix() {
    float scale;
    final int viewWidth = getWidth() - getPaddingLeft() - getPaddingRight();
    final int viewHeight = getHeight() - getPaddingTop() - getPaddingBottom();
    final int drawableWidth = getDrawable().getIntrinsicWidth();
    final int drawableHeight = getDrawable().getIntrinsicHeight();
    if (drawableWidth * viewHeight > drawableHeight * viewWidth) {
        scale = (float) viewHeight / (float) drawableHeight;
    } else {
        scale = (float) viewWidth / (float) drawableWidth;
    }
    return scale;
}

private void moveTo(float move, float scale) {
    //利用矩阵进行图片的缩放和位移
    Matrix imageMatrix = getImageMatrix();
    if (scale != 1) {
        // 先对图片进行比例缩放
        imageMatrix.setScale(scale, scale);
    }
    float[] matrixValues = new float[9];
    imageMatrix.getValues(matrixValues);
    float current = matrixValues[Matrix.MTRANS_Y];
    // 图片水平垂直移动
    imageMatrix.postTranslate(0, move - current);
    setImageMatrix(imageMatrix);
    invalidate();
}

另外还写了一个viewpager的滑动视差，和开眼视频还有最近腾讯新出的一款本地音乐app（轻听）一样的效果。有兴趣的朋友，也就可以去看看：
github地址： https://github.com/daimaXZ/ParallaxDemo
demo下载地址：http://fir.im/ParallaxDemo
效果图：

ParallaxDemo.gif

以上！希望各位大大喜欢！
Thanks yayaa！