导航到列表末尾时，如何保持 RecyclerView 的最后一项焦点？

Question

我在我的电视开发中使用了水平方向的 RecyclerView，它由方向键控制从左到右导航列表。导航到列表的最右侧时，RecyclerView 的最后一项总是失去焦点。

那么如何在导航到列表末尾时保持最后一项的焦点？

Answer 1

我深入研究了RecyclerView的源代码，我在LayoutManager中找到了onInterceptFocusSearch方法，在RecyclerView的内部class。

/**
 * This method gives a LayoutManager an opportunity to intercept the initial focus search
 * before the default behavior of {@link FocusFinder} is used. If this method returns
 * null FocusFinder will attempt to find a focusable child view. If it fails
 * then {@link #onFocusSearchFailed(View, int, RecyclerView.Recycler, RecyclerView.State)}
 * will be called to give the LayoutManager an opportunity to add new views for items
 * that did not have attached views representing them. The LayoutManager should not add
 * or remove views from this method.
 *
 * @param focused The currently focused view
 * @param direction One of { @link View#FOCUS_UP}, {@link View#FOCUS_DOWN},
 *                  {@link View#FOCUS_LEFT}, {@link View#FOCUS_RIGHT},
 *                  {@link View#FOCUS_BACKWARD}, {@link View#FOCUS_FORWARD}
 * @return A descendant view to focus or null to fall back to default behavior.
 *         The default implementation returns null.
 */
public View onInterceptFocusSearch(View focused, int direction) {
    return null ;
}

这让 LayoutManager 有机会在使用 FocusFinder 的默认行为之前拦截初始焦点搜索。

所以我重写了下面的 onInterceptFocusSearch ，并为我的 RecylerView 使用了 CustomGridLayoutManager，它工作起来很迷人。

public class CustomGridLayoutManager extends android.support.v7.widget.GridLayoutManager {

        public CustomGridLayoutManager(Context context, AttributeSet attrs, int defStyleAttr,
                                 int defStyleRes) {
            super (context, attrs, defStyleAttr, defStyleRes);
        }

        public CustomGridLayoutManager(Context context, int spanCount) {
            super (context, spanCount);
        }

        public CustomGridLayoutManager(Context context, int spanCount, int orientation,
                                 boolean reverseLayout) {
            super (context, spanCount, orientation, reverseLayout);
        }

        @Override
        public View onInterceptFocusSearch(View focused, int direction) {
            int pos = getPosition(focused);
            int count = getItemCount();
            int orientation = getOrientation();


            **********
            do some logic
            what i did was return the focused View when the focused view is the last item of RecyclerView.
            **********

            return super .onInterceptFocusSearch(focused, direction);
        }
}

Answer 2

受this issues启发，还有另一种解决方法：在 RecyclerView.Adapter<ViewHolder>

     int focusPos;

     @Override
        public void onBindViewHolder(ComposeViewHolder holder,
                final int position) {
            ....
            if (focusPos == position) { // focus last clicked view again
                holder.imageView.requestFocus();
            }
            ....
            holder.imageView.setOnClickListener(new OnClickListener() {
                @Override
                public void onClick(View v) {
                    ....
                    focusPos = position;
                    notifyDataSetChanged();
                }
            });
        }

Answer 3

如果您使用的是 BaseGridView 的子类，例如 HorizontalGridView 或 VerticalGridView，请设置一个 onKeyInterceptListener 来吞下列表末尾的移动键.例如，使用 HorizontalGridView:

grid.setOnKeyInterceptListener { event ->
    val focused = grid.focusedChild
    event?.keyCode == KEYCODE_DPAD_RIGHT && grid.layoutManager.getPosition(focused) == grid.adapter.itemCount-1
}

如果您直接使用 RecyclerView，则使用带有自定义 LinearLayoutManager 的 onInterceptFocusSearch。例如，对于 LinearLayoutManager.VERTICAL 列表：

list.layoutManager = object: LinearLayoutManager(context, LinearLayoutManager.VERTICAL, false) {
    override fun onInterceptFocusSearch(focused: View?, direction: Int): View? {
        if (direction == View.FOCUS_DOWN) {
            val pos = getPosition(focused)
            if (pos == itemCount-1)
                return focused
        }
        if (direction == View.FOCUS_UP) {
            val pos = getPosition(focused)
            if (pos == 0)
                return focused
        }
        return super.onInterceptFocusSearch(focused, direction)
    }
}

Answer 4

我正在为 Kotlin 添加一个答案。

如果您在每个地方都将覆盖基本布局，那么您的代码会变得复杂得多，尤其是因为在使用 TV 时您需要向布局管理器添加一些行为。

我用 D-PAD 在小米电视棒和 X62 Max 上检查过这个，也用模拟器，它有效。

所以我建议创建一个 class 这样的：

class TvLinearLayoutManager(
context: Context?,
orientation: Int,
reverseLayout: Boolean) : LinearLayoutManager(context, orientation, reverseLayout) {

override fun onInterceptFocusSearch(focused: View, direction: Int): View? {
    return if (
    // This prevent focus jumping near border items
        (getPosition(focused)==itemCount-1 && direction == View.FOCUS_RIGHT) ||
        (getPosition(focused)==0 && direction == View.FOCUS_LEFT)
    )
        focused
    else
        super.onInterceptFocusSearch(focused, direction)
}}

导航到列表末尾时，如何保持 RecyclerView 的最后一项焦点？

How to keep the last item's focus of RecyclerView when navigating to the end of the list?

android

android-tv

android-recyclerview