item里面放一个可以上下滑动的布局 about cardswipelayout HOT 7 OPEN

package com.yuqirong.cardswipeview;

import android.support.annotation.NonNull;
import android.support.v4.view.MotionEventCompat;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.helper.ItemTouchHelper;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewGroup;

/**
 * @author yuqirong
 */

public class CardLayoutManager extends RecyclerView.LayoutManager {

    private ItemTouchHelper mItemTouchHelper;

    private float mPrevX;
    private float mPrevY;

    public CardLayoutManager(@NonNull RecyclerView recyclerView, @NonNull ItemTouchHelper itemTouchHelper) {
        this.mItemTouchHelper = checkIsNull(itemTouchHelper);
        recyclerView.addOnItemTouchListener(new RecyclerView.OnItemTouchListener() {
            @Override
            public boolean onInterceptTouchEvent(RecyclerView rv, MotionEvent event) {
                View child = rv.findChildViewUnder(event.getX(), event.getY());
                if (child != null) {
                    RecyclerView.ViewHolder childViewHolder = rv.getChildViewHolder(child);
                    switch (MotionEventCompat.getActionMasked(event)) {
                        case MotionEvent.ACTION_DOWN:
                            mPrevX = event.getX();
                            mPrevY = event.getY();
                            break;

                        case MotionEvent.ACTION_MOVE:
                            float eventX = event.getX();
                            float eventY = event.getY();
                            float xDiff = Math.abs(eventX - mPrevX);
                            float yDiff = Math.abs(eventY - mPrevY);
                            if (xDiff > yDiff) {
                                mItemTouchHelper.startSwipe(childViewHolder);
                            }
                            break;
                        default:
                            break;
                    }
                }
                return false;
            }

            @Override
            public void onTouchEvent(RecyclerView rv, MotionEvent e) {
            }

            @Override
            public void onRequestDisallowInterceptTouchEvent(boolean disallowIntercept) {
            }
        });
    }

    private <T> T checkIsNull(T t) {
        if (t == null) {
            throw new NullPointerException();
        }
        return t;
    }

    @Override
    public RecyclerView.LayoutParams generateDefaultLayoutParams() {
        return new RecyclerView.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT);
    }

    @Override
    public void onLayoutChildren(final RecyclerView.Recycler recycler, RecyclerView.State state) {
        // 先把所有的View先从RecyclerView中detach掉，然后标记为"Scrap"状态，表示这些View处于可被重用状态(非显示中)。
        // 实际就是把View放到了Recycler中的一个集合中。
        detachAndScrapAttachedViews(recycler);
        int itemCount = getItemCount();
        for (int position = itemCount > CardConfig.DEFAULT_SHOW_ITEM ? CardConfig.DEFAULT_SHOW_ITEM : itemCount - 1; position >= 0; position--) {
            // 遍历Recycler中保存的View取出来
            final View view = recycler.getViewForPosition(position);
            // 因为刚刚进行了detach操作，所以现在可以重新添加
            addView(view);
            // 通知测量view的margin值
            measureChildWithMargins(view, 0, 0);
            // 计算view实际大小，包括了ItemDecorator中设置的偏移量
            int width = getDecoratedMeasuredWidth(view);
            int height = getDecoratedMeasuredHeight(view);
            int widthSpace = getWidth() - width;
            int heightSpace = getHeight() - height;
            // 指定了该View的显示区域，并将View显示上去，此时所有区域都用于显示View
            layoutDecoratedWithMargins(view, widthSpace / 2, heightSpace / 2, widthSpace / 2 + width, heightSpace / 2 + height);

            if (position == CardConfig.DEFAULT_SHOW_ITEM) {
                view.setScaleX(1 - (position - 1) * CardConfig.DEFAULT_SCALE);
                view.setScaleY(1 - (position - 1) * CardConfig.DEFAULT_SCALE);
                view.setTranslationY((position - 1f) * view.getMeasuredHeight() / CardConfig.DEFAULT_TRANSLATE_Y);
            } else if (position > 0) {
                view.setScaleX(1 - position * CardConfig.DEFAULT_SCALE);
                view.setScaleY(1 - position * CardConfig.DEFAULT_SCALE);
                view.setTranslationY(position * view.getMeasuredHeight() / CardConfig.DEFAULT_TRANSLATE_Y);
            }
        }
    }
}