Android开发中RecyclerView模仿探探左右滑动布局功能

public class OverLayCardLayoutManager extends RecyclerView.LayoutManager {
 private static final String TAG = "swipecard";
 public static int MAX_SHOW_COUNT = 4;
 public static float SCALE_GAP = 0.05f;
 public static int TRANS_Y_GAP;
 public OverLayCardLayoutManager(Context context) {
  //平移时, 需要用到的参考值
  TRANS_Y_GAP = (int) (20 * context.getResources().getDisplayMetrics().density);
 }
 @Override
 public RecyclerView.LayoutParams generateDefaultLayoutParams() {
  //必须要实现的方法
  return new RecyclerView.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT);
 }
 @Override
 public void onLayoutChildren(RecyclerView.Recycler recycler, RecyclerView.State state) {
  //在这个方法中进行View的布局操作.此方法会被调用多次.
  detachAndScrapAttachedViews(recycler);
  int itemCount = getItemCount();
  if (itemCount < 1) {
   return;
  }
  //top-3View的position
  int bottomPosition;
  //边界处理
  if (itemCount < MAX_SHOW_COUNT) {
   bottomPosition = 0;
  } else {
   bottomPosition = itemCount - MAX_SHOW_COUNT;
  }
  //从可见的最底层View开始layout，依次层叠上去
  for (int position = bottomPosition; position < itemCount; position++) {
   //1:重recycler的缓存机制中拿到一个View
   View view = recycler.getViewForPosition(position);
   //2:和自定义ViewGroup一样, 需要先addView
   addView(view);
   //3:和自定义ViewGroup一样, 也需要测量View的大小
   measureChildWithMargins(view, 0, 0);
   int widthSpace = getWidth() - getDecoratedMeasuredWidth(view);
   int heightSpace = getHeight() - getDecoratedMeasuredHeight(view);
   //4:和自定义ViewGroup的onLayout一样, 需要layout View.对View进行布局 
   //我们在布局时，将childView居中处理，这里也可以改为只水平居中
   layoutDecoratedWithMargins(view, widthSpace / 2, heightSpace / 2,
     widthSpace / 2 + getDecoratedMeasuredWidth(view),
     heightSpace / 2 + getDecoratedMeasuredHeight(view));
   /**
    * TopView的Scale 为1，translationY 0
    * 每一级Scale相差0.05f，translationY相差7dp左右
    *
    * 观察人人影视的UI，拖动时，topView被拖动，Scale不变，一直为1.
    * top-1View 的Scale慢慢变化至1，translation也慢慢恢复0
    * top-2View的Scale慢慢变化至 top-1View的Scale，translation 也慢慢变化只top-1View的translation
    * top-3View的Scale要变化，translation岿然不动
    */
   //第几层,举例子，count =7， 最后一个TopView（6）是第0层，
   int level = itemCount - position - 1;
   //如果不需要缩放平移, 那么下面的代码可以注释掉...
   //除了顶层不需要缩小和位移
   if (level > 0 /*&& level < mShowCount - 1*/) {
    //每一层都需要X方向的缩小
    view.setScaleX(1 - SCALE_GAP * level);
    //前N层，依次向下位移和Y方向的缩小
    if (level < MAX_SHOW_COUNT - 1) {
     view.setTranslationY(TRANS_Y_GAP * level);
     view.setScaleY(1 - SCALE_GAP * level);
    } else {//第N层在 向下位移和Y方向的缩小的成都与 N-1层保持一致
     view.setTranslationY(TRANS_Y_GAP * (level - 1));
     view.setScaleY(1 - SCALE_GAP * (level - 1));
    }
   }
  }
 }
}

public class RenRenCallback extends ItemTouchHelper.SimpleCallback {
 private static final String TAG = "RenRen";
 private static final int MAX_ROTATION = 15;
 OnSwipeListener mSwipeListener;
 boolean isSwipeAnim = false;
 public RenRenCallback() {
  //第一个参数决定可以拖动排序的方向, 这里由于不需要拖动排序,所以传0
  //第二个参数决定可以支持滑动的方向,这里设置了上下左右都可以滑动.
  super(0, ItemTouchHelper.DOWN | ItemTouchHelper.UP | ItemTouchHelper.LEFT | ItemTouchHelper.RIGHT);
 }
 public void setSwipeListener(OnSwipeListener swipeListener) {
  mSwipeListener = swipeListener;
 }
 //水平方向是否可以被回收掉的阈值
 public float getThreshold(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder) {
  //2016 12 26 考虑 探探垂直上下方向滑动，不删除卡片，这里参照源码写死0.5f
  return recyclerView.getWidth() * /*getSwipeThreshold(viewHolder)*/ 0.5f;
 }
 @Override
 public boolean onMove(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, RecyclerView.ViewHolder target) {
  //由于不支持滑动排序, 所以不需要处理此方法
  return false;
 }
 @Override
 public void onSwiped(RecyclerView.ViewHolder viewHolder, int direction) {
  //当view需要滑动的时候,会回调此方法
  //但是这个方法只是告诉你View需要滑动, 并不是对View和Adapter进行额外的操作,
  //所以, 如果你需要实现滑动删除, 那么需要在此方法中remove item等.
  //我们这里需要对滑动过后的View,进行恢复操作. 
  viewHolder.itemView.setRotation(0);//恢复最后一次的旋转状态
  if (mSwipeListener != null) {
   mSwipeListener.onSwipeTo(viewHolder, 0);
  }
  notifyListener(viewHolder.getAdapterPosition(), direction);
 }
 private void notifyListener(int position, int direction) {
  Log.w(TAG, "onSwiped: " + position + " " + direction);
  if (mSwipeListener != null) {
   mSwipeListener.onSwiped(position, direction);
  }
 }
 @Override
 public float getSwipeThreshold(RecyclerView.ViewHolder viewHolder) {
  //滑动的比例达到多少之后, 视为滑动
  return 0.3f;
 }
 @Override
 public void onChildDraw(Canvas c, RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, float dX, float dY, int actionState, boolean isCurrentlyActive) {
  super.onChildDraw(c, recyclerView, viewHolder, dX, dY, actionState, isCurrentlyActive);
  //当你在滑动的过程中, 此方法一直会被回调, 就跟onTouch事件一样...
  //先根据滑动的dx dy 算出现在动画的比例系数fraction
  float swipeValue = (float) Math.sqrt(dX * dX + dY * dY);
  final float threshold = getThreshold(recyclerView, viewHolder);
  float fraction = swipeValue / threshold;
  //边界修正 最大为1
  if (fraction > 1) {
   fraction = 1;
  } else if (fraction < -1) {
   fraction = -1;
  }
  //对每个ChildView进行缩放 位移
  int childCount = recyclerView.getChildCount();
  for (int i = 0; i < childCount; i++) {
   View child = recyclerView.getChildAt(i);
   //第几层,举例子，count =7， 最后一个TopView（6）是第0层，
   int level = childCount - i - 1;
   if (level > 0) {
    child.setScaleX(1 - SCALE_GAP * level + fraction * SCALE_GAP);
    if (level < MAX_SHOW_COUNT - 1) {
     child.setScaleY(1 - SCALE_GAP * level + fraction * SCALE_GAP);
     child.setTranslationY(TRANS_Y_GAP * level - fraction * TRANS_Y_GAP);
    } else {
     //child.setTranslationY((float) (mTranslationYGap * (level - 1) - fraction * mTranslationYGap));
    }
   } else {
    //最上层
    //rotate
    if (dX < -50) {
     child.setRotation(-fraction * MAX_ROTATION);
    } else if (dX > 50) {
     child.setRotation(fraction * MAX_ROTATION);
    } else {
     child.setRotation(0);
    }
    if (mSwipeListener != null) {
     RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams();
     final int adapterPosition = params.getViewAdapterPosition();
     mSwipeListener.onSwipeTo(recyclerView.findViewHolderForAdapterPosition(adapterPosition), dX);
    }
   }
  }
 }
 //扩展实现:点击按钮实现左滑效果
 public void toLeft(RecyclerView recyclerView) {
  if (check(recyclerView)) {
   animTo(recyclerView, false);
  }
 }
 //扩展实现:点击按钮实现右滑效果
 public void toRight(RecyclerView recyclerView) {
  if (check(recyclerView)) {
   animTo(recyclerView, true);
  }
 }
 private void animTo(final RecyclerView recyclerView, boolean right) {
  final int position = recyclerView.getAdapter().getItemCount() - 1;
  final View view = recyclerView.findViewHolderForAdapterPosition(position).itemView;
  TranslateAnimation translateAnimation = new TranslateAnimation(Animation.RELATIVE_TO_SELF, 0,
    Animation.RELATIVE_TO_SELF, right ? 1f : -1f,
    Animation.RELATIVE_TO_SELF, 0f, Animation.RELATIVE_TO_SELF, 1.3f);
  translateAnimation.setFillAfter(true);
  translateAnimation.setDuration(300);
  translateAnimation.setInterpolator(new DecelerateInterpolator());
  translateAnimation.setAnimationListener(new Animation.AnimationListener() {
   @Override
   public void onAnimationStart(Animation animation) {
   }
   @Override
   public void onAnimationEnd(Animation animation) {
    isSwipeAnim = false;
    recyclerView.removeView(view);
    notifyListener(position,
      x > view.getMeasuredWidth() / 2
        ?
        ItemTouchHelper.RIGHT : ItemTouchHelper.LEFT);
   }
   @Override
   public void onAnimationRepeat(Animation animation) {
   }
  });
  view.startAnimation(translateAnimation);
 }
 private boolean check(RecyclerView recyclerView) {
  if (isSwipeAnim) {
   return false;
  }
  if (recyclerView == null || recyclerView.getAdapter() == null) {
   return false;
  }
  if (recyclerView.getAdapter().getItemCount() == 0) {
   return false;
  }
  isSwipeAnim = true;
  return true;
 }
 public interface OnSwipeListener {
  /**
   * @param direction {@link ItemTouchHelper#LEFT} / {@link ItemTouchHelper#RIGHT}
   *     {@link ItemTouchHelper#UP} or {@link ItemTouchHelper#DOWN}).
   */
  void onSwiped(int adapterPosition, int direction);
  /**
   * 最上层View滑动时回调.
   *
   * @param viewHolder 最上层的ViewHolder
   * @param offset  距离原始位置的偏移量
   */
  void onSwipeTo(RecyclerView.ViewHolder viewHolder, float offset);
 }
 public static class SimpleSwipeCallback implements OnSwipeListener {
  /**
   * {@inheritDoc}
   */
  @Override
  public void onSwiped(int adapterPosition, int direction) {
  }
  /**
   * {@inheritDoc}
   */
  @Override
  public void onSwipeTo(RecyclerView.ViewHolder viewHolder, float offset) {
  }
 }
}