如何在Android TV上的RecyclerView中实现滚动？

Question

我有一个应用程序，我需要适应Android TV。此应用程序包含水平RecyclerView，当我按遥控器上的D-pad按钮时它不会滚动。我找到了this solution，但它崩溃了。这是代码：

<ru.myapp.package.HorizontalPersistentFocusWrapper
    android:layout_width="wrap_content"
    android:layout_height="wrap_content">
       <android.support.v7.widget.RecyclerView
           android:id="@+id/recycler_view"
           android:layout_width="match_parent"
           android:layout_height="250dp"
           android:background="@null"
           android:scrollbars="none"/>
</ru.myapp.package.HorizontalPersistentFocusWrapper>

Horizo​​ntalPersistentFocusWrapper与PersistentFocusWrapper相同，但mPersistFocusVertical = false;

在这个地方发生崩溃：

@Override
    public void requestChildFocus(View child, View focused) {
        super.requestChildFocus(child, focused);
        View view = focused;
        while (view != null && view.getParent() != child) {
            view = (View) view.getParent(); <<<------ Crash here
        }
        mSelectedPosition = view == null ? -1 : ((ViewGroup) child).indexOfChild(view);
        if (DEBUG) Log.v(TAG, "requestChildFocus focused " + focused + " mSelectedPosition " + mSelectedPosition);
    }

崩溃堆栈跟踪：

java.lang.ClassCastException: android.view.ViewRootImpl cannot be cast to android.view.View
         at ru.myapp.package.HorizontalPersistentFocusWrapper.requestChildFocus(HorizontalPersistentFocusWrapper.java:108)
         at android.view.View.handleFocusGainInternal(View.java:5465)
         at android.view.ViewGroup.handleFocusGainInternal(ViewGroup.java:714)
         at android.view.View.requestFocusNoSearch(View.java:8470)
         at android.view.View.requestFocus(View.java:8449)
         at android.view.ViewGroup.requestFocus(ViewGroup.java:2747)
         at android.view.View.requestFocus(View.java:8416)
         at android.support.v4.widget.NestedScrollView.arrowScroll(NestedScrollView.java:1222)
         at android.support.v4.widget.NestedScrollView.executeKeyEvent(NestedScrollView.java:551)
         at android.support.v4.widget.NestedScrollView.dispatchKeyEvent(NestedScrollView.java:512)
         at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1640)
         at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1640)

Answer 1

使用最新版本的RecyclerView。或者至少使用 com.android.support:recyclerview-v7:23.2.0 有关详细信息，请参阅此链接： https://code.google.com/p/android/issues/detail?id=190526&thanks=190526&ts=1445108573

现在重要的部分： 新版本的RecyclerView开始遵守其子女的规则（如身高和宽度）。您必须将子项XML中的根视图设置为： android:focusable="true"

现在，滚动将像预期的那样。

Answer 2

试试这个。适合我。

    @Override
public void requestChildFocus(View child, View focused) {
    super.requestChildFocus(child, focused);
    View view = focused;
    while (view != null && view.getParent() != child) {
        try {
            view = (View) view.getParent();
        } catch (ClassCastException e) {
            view = null;
        }
    }
    mSelectedPosition = view == null ? -1 : ((ViewGroup) child).indexOfChild(view);
    if (DEBUG)
        Log.v(TAG, "requestChildFocus focused " + focused + " mSelectedPosition " + mSelectedPosition);
}

Answer 3

在recyclerview项的根视图中将focusable设置为true。 android:focusable="true"并将选择器背景应用于根视图项。一切都可以在xml文件中完成。通过以下设置，dpad或遥控器将能够在列表中上下滚动，列表中当前选定的项目将突出显示。

RecyclerView：list_item.xml中列表项的根视图的布局文件，这里的重要部分是android:background="@drawable/item_selector"和android:focusable="true"

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:background="@drawable/item_selector"
    android:focusable="true">
    <TextView
        android:id="@+id/topic"
        android:layout_width="match_parent"
        android:layout_height="60dp"
        android:textColor="#ffffff"
        android:gravity="center"
        tools:text="Education"/>
</LinearLayout>

drawable文件夹中的drawable选择器文件：item_selector.xml

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
<item android:drawable="#000000" android:state_pressed="true"/>
<item android:drawable="#000000" android:state_selected="true"/>
<item android:drawable="#000000" android:state_focused="true"/>
<item android:drawable="#03A9F4"></item>
</selector>

包含RecyclerView：activity_main.xml的布局文件

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
                                             xmlns:tools="http://schemas.android.com/tools"
                                             android:layout_width="match_parent"
                                             android:layout_height="match_parent"
                                             xmlns:app="http://schemas.android.com/apk/res-auto"
                                             tools:context=".MainActivity">

    <android.support.v7.widget.RecyclerView
            android:id="@+id/recycler_view"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:scrollbars="none"
            app:layout_constraintTop_toTopOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintBottom_toBottomOf="parent"/>

</android.support.constraint.ConstraintLayout>