Android TV开发 焦点返回ListView时， 返回到离开时的位置

最近在开发一个ICNTV海外 TV端的项目，遇到一个小需求。

具体功能描述： 最左边布局一个ListView 用于显示分类列表，右侧布局一个gridview 用于展示视频列表信息。 当从listview 切换到gridview时再返回时，会选择离当前焦点位置最近的Item 作为下一个焦点的捕获点。onFocusChanged源码，

final ListAdapter adapter = mAdapter;

int closetChildIndex = -1;

int closestChildTop = 0;

if (adapter != null && gainFocus && previouslyFocusedRect != null) {

previouslyFocusedRect.offset(mScrollX, mScrollY);

// Don't cache the result of getChildCount or mFirstPosition here,

// it could change in layoutChildren.

if (adapter.getCount() < getChildCount() + mFirstPosition) {

mLayoutMode = LAYOUT_NORMAL;

layoutChildren();

}

// figure out which item should be selected based on previously

// focused rect

Rect otherRect = mTempRect;

int minDistance = Integer.MAX_VALUE;

final int childCount = getChildCount();

final int firstPosition = mFirstPosition;

for (int i = 0; i < childCount; i++) {

// only consider selectable views

if (!adapter.isEnabled(firstPosition + i)) {

continue;

}

View other = getChildAt(i);

other.getDrawingRect(otherRect);

offsetDescendantRectToMyCoords(other, otherRect);

//遍历listview的child，并获取direction方向的距离

int distance = getDistance(previouslyFocusedRect, otherRect, direction);

if (distance < minDistance) {

minDistance = distance;

closetChildIndex = i;

closestChildTop = other.getTop();

}

}

}

if (closetChildIndex >= 0) {

setSelectionFromTop(closetChildIndex + mFirstPosition, closestChildTop);

} else {

requestLayout();

}

此时，需要重写onFocusChanged，记录焦点改变时的位置，当listview获取焦点时，调用listview的setSelectionFromTop方法。如果调用setSelection会出现滑动效果。

protected void onFocusChanged(boolean gainFocus, int direction,

Rect previouslyFocusedRect) {

int lastSelectItem = getSelectedItemPosition();

super.onFocusChanged(gainFocus, direction, previouslyFocusedRect);

if (gainFocus) {

//获取焦点离开前的selection位置聚listview顶端位置，通过setSelectionFromTop方法，避免出现滑动效果。

View other = getChildAt(lastSelectItem);

int top = (other== null) ? 0 : other.getTop();

setSelectionFromTop(lastSelectItem, top);

}

}