Android TV应用 RecyclerView 焦点乱跑问题解决

本文只讨论如何解决Android TV应用 RecyclerView 焦点乱跑的问题.

RecyclerView的使用方法，大家可以参考此篇博文：http://blog.csdn.net/lmj623565791/article/details/45059587

使用示例：

public static final int ITEMS_COUNT_ONE_LINE = 6;
mRecyclerView = (RecyclerView) root.findViewById(R.id.rv);
mGridLayoutManager = new FocusGridLayoutManager(getContext(), ITEMS_COUNT_ONE_LINE);
mGridLayoutManager.setOrientation(RecyclerView.VERTICAL);
mRecyclerView.setLayoutManager(mGridLayoutManager);

解决此问题的核心是修改 FocusGridLayoutManager

public class FocusGridLayoutManager extends android.support.v7.widget.GridLayoutManager {
}

在此GridlayoutManager中，重载方法onInterceptFocusSearch

@Override
    public View onInterceptFocusSearch(View focused, int direction) {
        if (direction == View.FOCUS_DOWN) {
            int pos = getPosition(focused);
            int nextPos = getNextViewPos(pos, direction);
            int size = getChildCount();
            int count = getItemCount();
            if (size > 0) {
                int startIndex = 0;
                if (size >= mSpanCount) {
                    startIndex = size - mSpanCount;
                }
                View view;
                for (int i = startIndex; i < size; i++) {
                    view = getChildAt(i);
                    if (view == focused) {
                        int lastVisibleItemPos = findLastCompletelyVisibleItemPosition();
                        if (pos > lastVisibleItemPos) { //lastVisibleItemPos==-1 ||
                            return focused;
                        } else {
                            int lastLineStartIndex = 0;
                            if (count >= mSpanCount) {
                                lastLineStartIndex = count - mSpanCount;
                            }
                            if (pos >= lastLineStartIndex && pos < count) { //最后一排的可见view时,返回当前view
                                return focused;
                            }
                            break;
                        }
                    }
                }
            } else {
                return focused;
            }
        }
        return super .onInterceptFocusSearch(focused, direction);
    }

最核心的是两个地方

1.if (pos > lastVisibleItemPos)  若当前要显示的位置，大于可见的Item的位置，即此时，有可能焦点会乱跑了，此时，返回当前的View作为下一个要Focus的View.

 2.if (pos >= lastLineStartIndex && pos < count)  最后一排的可见view时,返回当前view，避免会加载看不见的view,此时也会乱跑。

至此，解决了乱跑问题。其他类型的LayoutManager也可照此方法解决。