Android实现可拖动层叠卡片布局

公司app要求做一个扭蛋功能，其实就是一个可拖动层叠卡片列表，原理还是由一个自定义Recyclerview和LayoutManager来实现

自定义RecyclerView很简单,只是修改touch事件，防止点击到卡片外还被处理的情况

@Override
    public boolean onTouchEvent(MotionEvent e) {
        if(e.getY()< UIUtil.dip2px(TutuApplication.getInstance().getContext(),95)||e.getY()>getHeight()-UIUtil.dip2px(TutuApplication.getInstance().getContext(),95)){
            if(e.getAction()!=MotionEvent.ACTION_UP && e.getAction()!=MotionEvent.ACTION_MOVE) {
                return false;
            }
        }
        return super.onTouchEvent(e);
    }

实际的层叠效果还是需要LayoutManager来实现

public class SwipeCardLayoutManager extends RecyclerView.LayoutManager {
    Context context;
    int TRANS_Y_GAP;
    public SwipeCardLayoutManager(Context context){
        TRANS_Y_GAP= (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP,15,
                context.getResources().getDisplayMetrics());
    }
    @Override
    public RecyclerView.LayoutParams generateDefaultLayoutParams() {
        return new RecyclerView.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT,
                ViewGroup.LayoutParams.WRAP_CONTENT);
    }

    @Override
    public void onLayoutChildren(RecyclerView.Recycler recycler, RecyclerView.State state) {
        super.onLayoutChildren(recycler, state);
        //1.如何实现层叠效果--cardView.layout(l,t,r,b)
        //2.如何让8个条目中的4个展示在RecylerView里面
        //1在布局layout之前，将所有的子View先全部detach掉，然后放到Scrap集合里面缓存。
        detachAndScrapAttachedViews(recycler);
        //2)只将最上面4个view添加到RecylerView容器里面
        int itemCount=getItemCount();//8个
        int bottomPosition;
        if(itemCount< CardConfig.MAX_SHOW_COUNT){
            bottomPosition=0;

        }else{
            bottomPosition=itemCount-CardConfig.MAX_SHOW_COUNT;
        }
        for(int i=bottomPosition;i<itemCount;i++){
            View view=recycler.getViewForPosition(i);
            addView(view);
            measureChildWithMargins(view,0,0);
            int widthSpace=getWidth()-getDecoratedMeasuredWidth(view);
            int heightSpace=getHeight()-getDecoratedMeasuredHeight(view);
            //摆放cardView
            //层叠效果--Scale+TranslationY
            //层级的位置关系1/2/3/4
            int level=itemCount-i-1;
            layoutDecorated(view,
                    widthSpace/2,
                    heightSpace/2+StatusBarUtil.getStatusBarHeight(TutuApplication.getInstance().getContext()),
                    widthSpace/2+getDecoratedMeasuredWidth(view),
                    heightSpace/2+StatusBarUtil.getStatusBarHeight(TutuApplication.getInstance().getContext())+getDecoratedMeasuredHeight(view));

            if(level>0){
                if(level<CardConfig.MAX_SHOW_COUNT){
                    view.setTranslationY(CardConfig.TRANS_V_GAP*level*1.3f);
                    view.setScaleX(1-CardConfig.SCALE_GAP*level);
                    view.setScaleY(1-CardConfig.SCALE_GAP*level);
                }
            }else {
                view.setTranslationY(CardConfig.TRANS_V_GAP*(level-1));
                view.setScaleX(1-CardConfig.SCALE_GAP*(level-1));
                view.setScaleY(1-CardConfig.SCALE_GAP*(level-1));
            }
        }

    }
}

显示出来就是这个样子

对于滑动显示下一张，则使用自定义ItemTouchHelper.simpleCallBack来展示

自定义itemTouchHelper.simpleCallBack

public class SwipeCardCallBack extends ItemTouchHelper.SimpleCallback {
    private GameGachaAdapter adapter;
    private RecyclerView mRv;
    private OnSwipeEndListener listener;
    private TextView tv;
    private int x = 1;
    private Context context;

    public void refresh(){
//        x = 1;
//        tv.setText(context.getResources().getString(R.string.explored)+(++x)+"/????");
        removeCard();
    }
    public SwipeCardCallBack(GameGachaAdapter adapter, RecyclerView mRv, TextView view, Context context) {
        super(0,
                ItemTouchHelper.LEFT | ItemTouchHelper.UP |
                        ItemTouchHelper.RIGHT | ItemTouchHelper.DOWN
        );
        this.adapter = adapter;
        this.mRv = mRv;
        this.tv = view;
        this.context = context;
    }
    public void addGameGachaList(List<IMulTypeHelper> mDatas){
        adapter.addAdapterData(0,mDatas);
        adapter.notifyDataSetChanged();
        listener.onSwipe();
    }
    public SwipeCardCallBack(int dragDirs, int swipeDirs) {
        super(dragDirs, swipeDirs);
    }

    public SwipeCardCallBack() {
        /*
        * 即我们对哪些方向操作关心。如果我们关心用户向上拖动，可以将
         填充swipeDirs参数为LEFT | RIGHT 。0表示从不关心。
        * */
        super(0,
                ItemTouchHelper.LEFT | ItemTouchHelper.UP |
                        ItemTouchHelper.RIGHT | ItemTouchHelper.DOWN
        );
    }

    @Override
    public boolean onMove(RecyclerView recyclerView,
                          RecyclerView.ViewHolder viewHolder,
                          RecyclerView.ViewHolder target) {
        return false;
    }

    @Override
    public void onSwiped(RecyclerView.ViewHolder viewHolder, int direction) {
        //当已经滑动删除了的时候会被回掉--删除数据，循环的效果
        removeCard();
    }

    public void removeCard() {
        if(adapter!=null && adapter.getItemCount()>0) {
            adapter.removeAdapterData(adapter.getItemCount() - 1);
//        mDatas.add(0, remove);
            adapter.notifyDataSetChanged();
            listener.onSwipe();
            if (adapter.getItemCount() == 6) {
                listener.onSwipeEnd();
            }
            tv.setText(context.getResources().getString(R.string.explored) + (++x) + "/????");
        }
    }

    @Override
    public void clearView(@NonNull RecyclerView recyclerView, @NonNull RecyclerView.ViewHolder viewHolder) {
        super.clearView(recyclerView, viewHolder);
    }

    @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);
        //监听话滑动的距离--控制动画的执行程度

        if(dY == 0f&&!isCurrentlyActive){
            int itemcount = recyclerView.getChildCount();
            for (int i = 0; i < itemcount; i++) {
                //执行
                View view = recyclerView.getChildAt(i);
                //几个view层叠的效果，错开的效果--便宜动画+缩放动画
                int level = itemcount - i - 1;
                view.setRotation(0);
                if(dX == 0) {
                    if(level>0){
                        if(level<CardConfig.MAX_SHOW_COUNT){
                            view.setTranslationY(CardConfig.TRANS_V_GAP*level*1.3f);
                            view.setScaleX(1-CardConfig.SCALE_GAP*level);
                            view.setScaleY(1-CardConfig.SCALE_GAP*level);
                        }
                    }else {
                        view.setTranslationY(CardConfig.TRANS_V_GAP*(level-1));
                        view.setScaleX(1-CardConfig.SCALE_GAP*(level-1));
                        view.setScaleY(1-CardConfig.SCALE_GAP*(level-1));
                    }
                }
            }
        }else {
            //灵界点
            double maxDistance = recyclerView.getWidth() * 1f;
            double distance = Math.sqrt(dX * dX)*2;
            //动画执行的百分比
            double fraction = distance / maxDistance;
            if (fraction > 1) {
                fraction = 1;
            }
            int itemcount = recyclerView.getChildCount();
            for (int i = 0; i < itemcount; i++) {
                //执行
                View view = recyclerView.getChildAt(i);
                //几个view层叠的效果，错开的效果--便宜动画+缩放动画
                int level = itemcount - i - 1;
                if(level == 0){//最外层动画
                    if(Math.abs(dX) == 1080f && dY == 0f&&!isCurrentlyActive){
                        view.setRotation(0);
                    }else {
                        if(dX<0){
                            view.setRotation((float) (360f - (30 * fraction)));
                        }else {
                            view.setRotation((float) (30 * fraction));
                        }
                    }
                } else if(level ==CardConfig.MAX_SHOW_COUNT-1){//最内层动画
                    view.setTranslationY((float) (CardConfig.TRANS_V_GAP*(level-fraction)*1.3f));
                    view.setScaleX((float) (1-CardConfig.SCALE_GAP*(level-fraction)));
                    view.setScaleY((float) (1-CardConfig.SCALE_GAP*(level-fraction)));
                }else if (level < CardConfig.MAX_SHOW_COUNT - 1) {
                    view.setTranslationY((float) ((level - (2*fraction)) * CardConfig.TRANS_V_GAP));
                    view.setScaleX((float) (1 - CardConfig.SCALE_GAP * level + fraction * (CardConfig.SCALE_GAP*2)));
                    view.setScaleY((float) (1 - CardConfig.SCALE_GAP * level + fraction * (CardConfig.SCALE_GAP*2)));
                }

            }
        }

    }

    @Override
    public void onSelectedChanged(@Nullable RecyclerView.ViewHolder viewHolder, int actionState) {
        super.onSelectedChanged(viewHolder, actionState);
    }

    public interface OnSwipeEndListener{
        void onSwipeEnd();
        void onSwipe();
    }
    public void setOnSwipeEndListener(OnSwipeEndListener listener){
        this.listener = listener;
    }
}

在Activity中:

private SwipeCardCallBack callback;
private ItemTouchHelper helper; 

...
helper = new ItemTouchHelper(callback);
 helper.attachToRecyclerView(swipeFlingAdapterView);
 callback.setOnSwipeEndListener(new SwipeCardCallBack.OnSwipeEndListener() {
            @Override
            public void onSwipeEnd() {
                swipeFlingAdapterView.suppressLayout(true);
                gameGachaRefresh.setClickable(false);
                ToastUtils.createToast().showCenter(TutuGameGachaActivity.this,getString(R.string.wait_moment));
                presenter.getGameGacha(PRESENTER_LOAD_STATE_REFRESH);
            }

            @Override
            public void onSwipe() {
                if(arrayAdapter.getItemCount()>0) {
                    swipe();
                }
            }

        });

这样实际效果就差不多可以了。

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