recyclerview 实现卡片滑动效果

╰+攻爆jí腚メ 2022-07-14 01:00 374阅读 0赞

想recyclerview快速实现卡片滑动，需要一个重要帮助类，LinearSnapHelper类,这个类是Android24.2.0之后引入的帮助类，是SnapHelper抽象类的子类

具有让recyclerview中的item居中的功能，实现也相当简单 LinearSnapHelper linearSnapHelper = new LinearSnapHelper(); linearSnapHelper.attachToRecyclerView(recycler); 相比于通过viewpager然后监听viewpager的滑动，实现要简单一点

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设置linearsnahelper只能让item选为居中，没有卡片滑动效果，接下来如果实现？

第一步：item的宽度，设置左右margin边距，让item左右有空白间隙；

@Override public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) { View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.my_recyclerview_item,parent,false); //这里设置view的宽度 RecyclerScaleUtils.onCreateViewHolder(parent,view,ScreenUtil.dip2px(parent.getContext(),30f)); return new MyViewHolder(view); } RecyclerScaleUtils类中的onCreateViewHolder方法，就是设置item的宽度 public static void onCreateViewHolder(ViewGroup parent, View itemView,int margin) {
        RecyclerView.LayoutParams lp = (RecyclerView.LayoutParams) itemView.getLayoutParams();
        if(margin <= 0){
            margin = mDefaultMargin;
        }
        lp.width = parent.getWidth() - 2*margin;
        itemView.setLayoutParams(lp);
      @Overridepublic void onBindViewHolder(MyViewHolder holder, int position) { //设置第一个与最后item对称显示 RecyclerScaleUtils.onBindViewHolder(holder.itemView,position, getItemCount(),ScreenUtil.dip2px(holder.itemView.getContext(),30f)); Glide.with(mContext).load(mList.get(position)).centerCrop().into(holder.mImageview);} //这里是处理最左边和最右边的宽度 public static void onBindViewHolder(View itemView, final int position, int itemCount,int margin) { int leftMarin = 0; int rightMarin = 0; int topMarin = 0; int bottomMarin = 0; if(position == 0){ leftMarin = margin; rightMarin = 0; }else if(position == (itemCount-1)){ leftMarin = 0; rightMarin = margin; } ViewGroup.MarginLayoutParams lp = (ViewGroup.MarginLayoutParams) itemView.getLayoutParams(); if (lp.leftMargin != leftMarin || lp.topMargin != topMarin || lp.rightMargin != rightMarin || lp.bottomMargin != bottomMarin) { lp.setMargins(leftMarin, topMarin, rightMarin, bottomMarin); itemView.setLayoutParams(lp); } }

第二步：就是在左右滑动的时候，当前item，和左右item都有相应的缩放效果；如左滑，当前item缩小，右边item，放大（这里可以用动画）

public void attachToRecyclerView(RecyclerView recyclerView,int margin){ if(recyclerView == null){ return; } mRecycler = recyclerView; if(margin <= 0){ mMargin = mDefaultMargin; }else { mMargin = margin; } initView(); final CustomLinearSnapHelper helper = new CustomLinearSnapHelper(); recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() { @Override public void onScrollStateChanged(RecyclerView recyclerView, int newState) { super.onScrollStateChanged(recyclerView, newState); if(newState == RecyclerView.SCROLL_STATE_IDLE){ if(mDistances == 0 || mDistances == (mItemCount*mItemwidth)){ helper.mStateIdle = true; }else{ helper.mStateIdle = false; } } } @Override public void onScrolled(RecyclerView recyclerView, int dx, int dy) { super.onScrolled(recyclerView, dx, dy); if(recyclerView.getLayoutManager().getLayoutDirection() == LinearLayoutManager.HORIZONTAL){ mDistances += dx; getCurrentPosition(); setItemScale(); } } }); helper.attachToRecyclerView(recyclerView); } //这里获取item的宽与countitem数 protected void initView( ){ mRecycler.post(new Runnable() { @Override public void run() { mItemCount = mRecycler.getAdapter().getItemCount(); mItemwidth = mRecycler.getWidth() - 2 * mMargin; mRecycler.smoothScrollToPosition(mCurrentPosition); setItemScale(); } }); } //item在滑动时，进行动画的缩放 public void setItemScale(){ View leftView = null; View rightView = null; if(mCurrentPosition > 0){ leftView = mRecycler.getLayoutManager().findViewByPosition(mCurrentPosition - 1); } View currentView = mRecycler.getLayoutManager().findViewByPosition(mCurrentPosition); if(mCurrentPosition < (mItemCount - 1)){ rightView = mRecycler.getLayoutManager().findViewByPosition(mCurrentPosition +1); } //滑动百分比，左右的都是放大，中间缩小 float percent = Math.abs((mDistances - mCurrentPosition * mItemwidth*1.0f)/mItemwidth); if(leftView != null){ //这里是缩小原来大小的0.8-1.0 左右0.8，中间1.0 0.8+(percent*0.2) leftView.setScaleY(0.8f+(percent*0.2f)); } if(currentView != null){ currentView.setScaleY(1-0.2f*percent); } if(rightView != null){ rightView.setScaleY(0.8f+(percent*0.2f)); } } protected void getCurrentPosition(){ if(mItemwidth <= 0) return; boolean change = false; if (Math.abs(mDistances - mCurrentPosition * mItemwidth) >= mItemwidth) { change = true; } if (change) { //这里是从0开始的 mCurrentPosition = mDistances / mItemwidth; } } public static void setItemPosition(int position){ this.mCurrentPosition = position; this.mDistances = position * mItemwidth; } 这里自定义了linearsanphelper,因为在第一个item和最后一个item设置了marginleft与rightmargin，导致这两个item的 中心位置滑动的偏移，此时LinearSnapHelper通过调用recyclerview的onscrolllistener获取不动具体的中心点，而误以为 客户一直在滑动，    
     public class CustomLinearSnapHelper extends LinearSnapHelper { public static boolean mStateIdle = false; /** // * int[] snapDistance = calculateDistanceToFinalSnap(layoutManager, snapView); // if (snapDistance[0] != 0 || snapDistance[1] != 0) { // mRecyclerView.smoothScrollBy(snapDistance[0], snapDistance[1]); // } // 这个方法返回的数组值，是让recyclerview移动并居中显示的,如果是第一个或者最后一个位置， // 因无法居中而调用recyclerview的OnScrollListener监听 // */ @Override public int[] calculateScrollDistance(int velocityX, int velocityY) { if(mStateIdle){ return new int[2]; }else{ int[] ints = super.calculateScrollDistance(velocityX, velocityY); for (int i:ints){ Log.e("tests","==i=="+i); } return super.calculateScrollDistance(velocityX, velocityY); } } }

recyclerView在设置适配器之后

RecyclerScaleUtils utils = new RecyclerScaleUtils(); utils.attachToRecyclerView(recycler,ScreenUtil.dip2px(this,30f));

demo链接http://download.csdn.net/detail/change987654321/9689690

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