Android-->RecyclerView模仿探探左右滑动布局

站在巨人的肩膀上,才能走得更远.

参考文章:http://blog.csdn.net/zxt0601/article/details/53730908

我在此基础上优化了部分代码, 添加了滑动回调, 可自定义性更强. 并且添加了点击按钮左右滑动的功能.

据说无图都不敢发文章了.
看图:

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1:这种功能, 首先需要自己管理布局

继承 RecyclerView.LayoutManager , 显示自己管理布局, 比如最多显示4个view, 并且都是居中显示.
底部的View还需要进行缩放,平移操作.

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));
                }
            }
        }
    }
}

2:布局好了之后, 就需要监听鼠标事件了

谷歌官方提供了一个ItemTouchHelper工具类, 对滑动进行了惨无人道的优越封装, 傻x都能用…
使用方法: new ItemTouchHelper(callback).attachToRecyclerView(recyclerView);就这么简单,
接下来的操作, 都在回调callback里面进行.

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) {

        }
    }
}

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看起来不难, 但是真正做的时候, 要处理的地方很多,

并且有些地方要思考很久, 才能实现效果.

总之,做了你才会发现1+1=2的魅力, just do it.

开源地址: https://github.com/angcyo/RecyclerLayoutManager

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