Android TV开发——RecyclerView For TV

Android TV开发——RecyclerView For TV"/>

Android TV开发——RecyclerView For TV

原文链接：重写RecyclerView使其在TV端运行

TV应用中使用原生RecyclerView使用时的局限性：
例如焦点显示不全，无法定位到某个position等等

下面总结下在TV端使用使用RecyclerView时踩过的坑

(一) 解决RecyclerView刷新数据的时候，焦点错乱问题

下面是google官方给出的解决方案

1. adapter调用setHasStableIds(true)方法

2. 重写getItemId()方法,让每个view都有各自的id

public abstract class BaseRecyclerAdapter<VH extends BaseRecyclerViewHolder, T> extends RecyclerView.Adapter<BaseRecyclerViewHolder> {public LayoutInflater mInflate;public List<T> mDataList;public BaseRecyclerAdapter(Context context, List<T> dataList)     {this.mInflate = LayoutInflater.from(context);this.mDataList = dataList;setHasStableIds(true);}public void setDataList(List<T> dataList) {this.mDataList = dataList;}public void addDataList(List<T> dataList) {if (dataList != null && dataList.size()>0) {this.mDataList.addAll(dataList);}}@Overridepublic int getItemCount() {return mDataList != null ? mDataList.size() : 0;}@Overridepublic long getItemId(int position) {return position;}public List<T> getDataList() {return mDataList;}@Overridepublic void onBindViewHolder(BaseRecyclerViewHolder holder, int position) {onBindBaseViewHolder((VH) holder, position);}public abstract VH onCreateViewHolder(ViewGroup parent, int viewType);protected abstract void onBindBaseViewHolder(VH viewHolder, int position);/*** @param hasStableIds 有多个observer的话会报错*/@Overridepublic void setHasStableIds(boolean hasStableIds) {super.setHasStableIds(hasStableIds);}
}

3. RecyclerView的动画必须去掉

setItemAnimator(null);

（二）解决长按遥控器，让RecyclerView快速滑动，焦点错乱问题

1. 由于长按遥控器的时候，RecyclerView找不到findFocusView为null，此时我就把RecyclerView的onKeyUp事件给屏蔽了

2. 通过FocusFind类找到view，并让view请求焦点；

3.focusFind焦点失败之后，如果是让其滑动item的宽度（左后滑动）或者高度（上下滑动），因为有可能滑到下面还有可能有item，否则RecyclerView将不会继续滑动

 @Overridepublic boolean dispatchKeyEvent(KeyEvent event) {if (mInterceptLister != null && mInterceptLister.onIntercept(event)) {return true;}boolean result = super.dispatchKeyEvent(event);View focusView = this.findFocus();if (focusView == null) {return result;} else {int dy = 0;int dx = 0;if (getChildCount() > 0) {View firstView = this.getChildAt(0);dy = firstView.getHeight();dx = firstView.getWidth();}if (event.getAction() == KeyEvent.ACTION_UP) {return true;} else {switch (event.getKeyCode()) {case KeyEvent.KEYCODE_DPAD_RIGHT:View rightView = FocusFinder.getInstance().findNextFocus(this, focusView, View.FOCUS_RIGHT);Log.i(TAG, "rightView is null:" + (rightView == null));if (rightView != null) {rightView.requestFocus();return true;} else {this.smoothScrollBy(dx, 0);return true;}case KeyEvent.KEYCODE_DPAD_LEFT:View leftView = FocusFinder.getInstance().findNextFocus(this, focusView, View.FOCUS_LEFT);Log.i(TAG, "leftView is null:" + (leftView == null));if (leftView != null) {leftView.requestFocus();return true;} else {this.smoothScrollBy(-dx, 0);return true;}case KeyEvent.KEYCODE_DPAD_DOWN:View downView = FocusFinder.getInstance().findNextFocus(this, focusView, View.FOCUS_DOWN);Log.i(TAG, " downView is null:" + (downView == null));if (downView != null) {downView.requestFocus();return true;} else {this.smoothScrollBy(0, dy);return true;}case KeyEvent.KEYCODE_DPAD_UP:View upView = FocusFinder.getInstance().findNextFocus(this, focusView, View.FOCUS_UP);Log.i(TAG, "upView is null:" + (upView == null));if (event.getAction() == KeyEvent.ACTION_UP) {return true;} else {if (upView != null) {upView.requestFocus();return true;} else {this.smoothScrollBy(0, -dy);return true;}}}}}return result;}

（三）解决RecyclerView 定位到某个item不获取焦点问题

RecyclerView仅仅提供了一个smoothScrollToPosition(int position)方法，而且该方法，能滑到指定的position位置，但是该position处的item并没有获取焦点。

想起在使用LeanBack中的RecyclerView时，你会发现它提供了专门定位到某个position，并获取焦点的方法。但是然后沉下心把源码给看了，终于明白了其中的原理，原来它在定位到指定位置的item后，找到目标的item，并让其主动请求焦点。完美解决

(1) RecyclerView的smoothScrollToPosition方法，最终执行的是LayoutManger的smoothScrollToPosition方法。下面是RecyclerView的
smoothScrollToPosition的源代码

  public void smoothScrollToPosition(int position) {if (mLayoutFrozen) {return;}if (mLayout == null) {Log.e(TAG, "Cannot smooth scroll without a LayoutManager set. " +"Call setLayoutManager with a non-null argument.");return;}mLayout.smoothScrollToPosition(this, mState, position);}

(2) RecyclerView弹性滑动是通过SmoothScroller来实现的，SmoothScroller中有onStart和onStop的回调，大胆猜测一下，onStop肯定是滑动结束的回调，于是找到targetView，并让其请求焦点，问题得以解决

/*** Created by liuyu on 17/2/8.* fix issue: RecyclerView 进行item定位的时候,item没有获取焦点*/
public class TvGridLayoutManager extends GridLayoutManager {public TvGridLayoutManager(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {super(context, attrs, defStyleAttr, defStyleRes);}public TvGridLayoutManager(Context context, int spanCount) {super(context, spanCount);}public TvGridLayoutManager(Context context, int spanCount, int orientation, boolean reverseLayout) {super(context, spanCount, orientation, reverseLayout);}/*** Base class which scrolls to selected view in onStop().*/abstract class GridLinearSmoothScroller extends LinearSmoothScroller {public GridLinearSmoothScroller(Context context) {super(context);}/*** 滑动完成后,让该targetPosition 处的item获取焦点*/@Overrideprotected void onStop() {super.onStop();View targetView = findViewByPosition(getTargetPosition());if (targetView != null) {targetView.requestFocus();}super.onStop();}}/*** RecyclerView的smoothScrollToPosition方法最终会执行smoothScrollToPosition* @param recyclerView* @param state* @param position*/@Overridepublic void smoothScrollToPosition(RecyclerView recyclerView, RecyclerView.State state,int position) {GridLinearSmoothScroller linearSmoothScroller =new GridLinearSmoothScroller(recyclerView.getContext()) {@Overridepublic PointF computeScrollVectorForPosition(int targetPosition) {return computeVectorForPosition(targetPosition);}};linearSmoothScroller.setTargetPosition(position);startSmoothScroll(linearSmoothScroller);}public PointF computeVectorForPosition(int targetPosition) {return superputeScrollVectorForPosition(targetPosition);}
}

为了方便大家我把代码上传到了github：