Leanback中focusOutFront在VerticalGridSupportFragment不生效问题

开发背景 #

我使用Leanback库开发Android TV应用，当前页面需要展示频道列表及对应EPG（电子节目指南）数据，已通过VerticalGridSupportFragment完成频道列表的加载渲染。页面同时设置了日期筛选按钮，支持按所选日期过滤EPG列表，频道列表、EPG区域与筛选按钮的布局如下图所示：

故障现象 #

当前焦点导航存在异常：

• 焦点可从筛选按钮正常移动到下方的频道列表区域
• 无法从频道列表反向移动回上方的筛选按钮，需要实现焦点从VerticalGridSupportFragment向前（front方向）移出、聚焦到外部其他视图的能力

我已尝试通过样式配置、自定义VerticalGridPresenter两种方式设置focusOutFront="true"，均未生效：目前仅start、end方向的焦点移出功能正常，front方向的焦点移出始终失效。相同配置在RowSupportFragment中可正常运行，仅在VerticalGridSupportFragment中不工作。

已尝试的无效方案 #

样式配置 #

尝试通过主题样式覆盖配置焦点移出属性，代码如下：

<style name="AppThemeLeanbackVerticalGridView" parent="AppThemeLeanback">
    <item name="headersVerticalGridStyle">@style/AppThemeLeanbackHeadersVerticalGridView</item>
    <item name="itemsVerticalGridStyle">@style/AppThemeLeanbackGridItemsVerticalGridView</item>
    <item name="rowsVerticalGridStyle">@style/AppThemeLeanbackHorizontalGridView</item>
</style>

<style name="AppThemeLeanbackHeadersVerticalGridView" parent="Widget.Leanback.Headers.VerticalGridView">
    <item name="focusOutFront">true</item>
    <item name="focusOutEnd">true</item>
    <item name="focusOutSideStart">true</item>
    <item name="focusOutSideEnd">true</item>
</style>

<style name="AppThemeLeanbackGridItemsVerticalGridView" parent="Widget.Leanback.GridItems.VerticalGridView">
    <item name="focusOutFront">true</item>
    <item name="focusOutEnd">true</item>
    <item name="focusOutSideStart">true</item>
    <item name="focusOutSideEnd">true</item>
</style>

<style name="AppThemeLeanbackHorizontalGridView" parent="Widget.Leanback.Rows.VerticalGridView">
    <item name="focusOutFront">true</item>
    <item name="focusOutEnd">true</item>
    <item name="focusOutSideStart">true</item>
    <item name="focusOutSideEnd">true</item>
</style>

自定义VerticalGridPresenter #

尝试自定义Presenter，在初始化GridView时手动设置焦点移出允许属性，代码如下：

class CustomVerticalGridPresenterFocusOut internal constructor(
    context: Context,
    private val padding: Int,
    focusZoomFactor: Int,
    useFocusDimmer: Boolean
) : VerticalGridPresenter(focusZoomFactor, useFocusDimmer) {

    private lateinit var gridView: VerticalGridView

    override fun initializeGridViewHolder(vh: ViewHolder) {
        super.initializeGridViewHolder(vh)
        gridView = vh.gridView
        val top = padding // 自定义顶部padding值
        val bottom = gridView.paddingBottom
        val right = gridView.paddingRight
        val left = gridView.paddingLeft
        gridView.setPadding(left, top, right, bottom)

        gridView.setFocusOutSideAllowed(throughStart = true, throughEnd = true)
        gridView.setFocusOutAllowed(throughFront = true, throughEnd = true)
    }
}

诉求 #

需要可行的解决方案，实现VerticalGridSupportFragment的front方向焦点移出功能。

内容的提问来源于stack exchange，提问作者Kabindra Shrestha