创建双窗格布局

试用 Compose 方式
Jetpack Compose 是推荐用于 Android 的界面工具包。了解如何在 Compose 中使用布局。

应用中的每个屏幕都必须能自适应并适应可用空间。您可以使用 ConstraintLayout 构建自适应界面,该界面支持将单窗格方法扩展到多种尺寸,但较大的设备可能会受益于将布局拆分为多个窗格。例如,您可能希望屏幕在所选项的详细信息列表旁边显示项列表。

SlidingPaneLayout 组件支持在较大的设备和可折叠设备上并排显示两个窗格,同时自动进行调整,在较小的设备(如手机)上一次仅显示一个窗格。

如需获取特定于设备的指南,请参阅屏幕兼容性概览

初始设置

如需使用 SlidingPaneLayout,请在应用的 build.gradle 文件中添加以下依赖项:

Groovy

dependencies {
    implementation "androidx.slidingpanelayout:slidingpanelayout:1.2.0"
}

Kotlin

dependencies {
    implementation("androidx.slidingpanelayout:slidingpanelayout:1.2.0")
}

XML 布局配置

SlidingPaneLayout 提供了一种水平的双窗格布局,可在界面的顶层使用。在这种布局中,第一个窗格用作内容列表或浏览器,从属于另一个窗格中用于显示内容的主要详细信息视图。

显示 SlidingPaneLayout 示例的图片
图 1. 使用 SlidingPaneLayout 创建的布局示例。

SlidingPaneLayout 会根据两个窗格的宽度来确定是否并排显示这些窗格。例如,如果测量后发现列表窗格的最小尺寸为 200 dp,详情窗格需要 400 dp,那么只要可用宽度不小于 600 dp,SlidingPaneLayout 就会自动并排显示两个窗格。

如果子视图的总宽度超过了 SlidingPaneLayout 中的可用宽度,这些视图就会重叠在一起。在这种情况下,子视图会展开,填充 SlidingPaneLayout 中的可用宽度。用户可以从屏幕的边缘拖回最顶层的视图以将其移开。

如果视图没有重叠,SlidingPaneLayout 支持在子视图上使用布局参数 layout_weight,以定义在测量完成后如何划分剩余空间。此参数仅与宽度相关。

在屏幕空间为并排显示两个视图的可折叠设备上,SlidingPaneLayout 会自动调整两个窗格的大小,使其位于重叠的折叠边或合页的两侧。在这种情况下,设置的宽度会被视为折叠功能两侧必须存在的最小宽度。如果没有足够的空间来维持该最小尺寸,SlidingPaneLayout 会切换回重叠视图。

下面这个示例使用了 SlidingPaneLayout,该布局将 RecyclerView 作为其左侧窗格,将 FragmentContainerView 作为其主要详细信息视图,用于显示左侧窗格中的内容:

<!-- two_pane.xml -->
<androidx.slidingpanelayout.widget.SlidingPaneLayout
   xmlns:android="http://schemas.android.com/apk/res/android"
   android:id="@+id/sliding_pane_layout"
   android:layout_width="match_parent"
   android:layout_height="match_parent">

   <!-- The first child view becomes the left pane. When the combined needed
        width, expressed using android:layout_width, doesn't fit on-screen at
        once, the right pane is permitted to overlap the left. -->
        
   <androidx.recyclerview.widget.RecyclerView
             android:id="@+id/list_pane"
             android:layout_width="280dp"
             android:layout_height="match_parent"
             android:layout_gravity="start"/>

   <!-- The second child becomes the right (content) pane. In this example,
        android:layout_weight is used to expand this detail pane to consume
        leftover available space when the entire window is wide enough to fit
        the left and right pane.-->
   <androidx.fragment.app.FragmentContainerView
       android:id="@+id/detail_container"
       android:layout_width="300dp"
       android:layout_weight="1"
       android:layout_height="match_parent"
       android:background="#ff333333"
       android:name="com.example.SelectAnItemFragment" />
</androidx.slidingpanelayout.widget.SlidingPaneLayout>

在此示例中,FragmentContainerView 上的 android:name 属性会将初始 fragment 添加到详情窗格中,从而确保使用大屏幕设备的用户在应用首次启动时不会看到空的右侧窗格。

以编程方式更换详细信息窗格

在前面的 XML 示例中,点按 RecyclerView 中的某个元素会触发详情窗格中的更改。在使用 fragment 时,这需要一个可替换右侧窗格的 FragmentTransaction,针对 SlidingPaneLayout 调用 open() 来更换为新的可见 fragment:

Kotlin

// A method on the Fragment that owns the SlidingPaneLayout,called by the
// adapter when an item is selected.
fun openDetails(itemId: Int) {
    childFragmentManager.commit {
        setReorderingAllowed(true)
        replace<ItemFragment>(R.id.detail_container,
            bundleOf("itemId" to itemId))
        // If it's already open and the detail pane is visible, crossfade
        // between the fragments.
        if (binding.slidingPaneLayout.isOpen) {
            setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE)
        }
    }
    binding.slidingPaneLayout.open()
}

Java

// A method on the Fragment that owns the SlidingPaneLayout, called by the
// adapter when an item is selected.
void openDetails(int itemId) {
    Bundle arguments = new Bundle();
    arguments.putInt("itemId", itemId);
    FragmentTransaction ft = getChildFragmentManager().beginTransaction()
            .setReorderingAllowed(true)
            .replace(R.id.detail_container, ItemFragment.class, arguments);
    // If it's already open and the detail pane is visible, crossfade
    // between the fragments.
    if (binding.getSlidingPaneLayout().isOpen()) {
        ft.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE);
    }
    ft.commit();
    binding.getSlidingPaneLayout().open();
}

具体来说,此代码不会对 FragmentTransaction 调用 addToBackStack(),这样可避免在详细信息窗格中构建返回堆栈。

本页中的示例直接使用 SlidingPaneLayout,并且要求您手动管理 fragment 事务。不过,导航组件通过AbstractListDetailFragment这个 API 类提供了双窗格布局的预构建实现,该 API 类在后台使用SlidingPaneLayout来管理列表和详情窗格。

这样,您就可以简化 XML 布局配置。您的布局只需要 FragmentContainerView 来保留 AbstractListDetailFragment 实现,而无需显式声明 SlidingPaneLayout 和这两个窗格:

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <androidx.fragment.app.FragmentContainerView
        android:id="@+id/two_pane_container"
        <!-- The name of your AbstractListDetailFragment implementation.-->
        android:name="com.example.testapp.TwoPaneFragment"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        <!-- The navigation graph for your detail pane.-->
        app:navGraph="@navigation/two_pane_navigation" />
</FrameLayout>

实现 onCreateListPaneView()onListPaneViewCreated(),为您的列表窗格提供自定义视图。对于详细信息窗格,AbstractListDetailFragment 会使用 NavHostFragment。这意味着,您可以定义仅包含要在详细信息窗格中显示的目的地的导航图。然后,您可以使用 NavController 在独立导航图中的目的地之间切换详细信息窗格:

Kotlin

fun openDetails(itemId: Int) {
    val navController = navHostFragment.navController
    navController.navigate(
        // Assume the itemId is the android:id of a destination in the graph.
        itemId,
        null,
        NavOptions.Builder()
            // Pop all destinations off the back stack.
            .setPopUpTo(navController.graph.startDestination, true)
            .apply {
                // If it's already open and the detail pane is visible,
                // crossfade between the destinations.
                if (binding.slidingPaneLayout.isOpen) {
                    setEnterAnim(R.animator.nav_default_enter_anim)
                    setExitAnim(R.animator.nav_default_exit_anim)
                }
            }
            .build()
    )
    binding.slidingPaneLayout.open()
}

Java

void openDetails(int itemId) {
    NavController navController = navHostFragment.getNavController();
    NavOptions.Builder builder = new NavOptions.Builder()
            // Pop all destinations off the back stack.
            .setPopUpTo(navController.getGraph().getStartDestination(), true);
    // If it's already open and the detail pane is visible, crossfade between
    // the destinations.
    if (binding.getSlidingPaneLayout().isOpen()) {
        builder.setEnterAnim(R.animator.nav_default_enter_anim)
                .setExitAnim(R.animator.nav_default_exit_anim);
    }
    navController.navigate(
        // Assume the itemId is the android:id of a destination in the graph.
        itemId,
        null,
        builder.build()
    );
    binding.getSlidingPaneLayout().open();
}

详情窗格导航图中的目的地不得存在于任何应用级外部导航图中。但是,详情窗格的导航图中的任何深层链接都必须附加到托管 SlidingPaneLayout 的目的地。这有助于确保外部深层链接先导航到 SlidingPaneLayout 目的地,然后再导航到详细信息窗格目的地的正确位置。

有关使用 Navigation 组件的双窗格布局的完整实现,请参阅 TwoPaneFragment 示例

与系统返回按钮集成

在列表窗格与详情窗格重叠的小尺寸设备上,请确保用户可通过系统返回按钮从详情窗格返回到列表窗格。为此,您可以提供自定义返回导航,并将 OnBackPressedCallbackSlidingPaneLayout 的当前状态相关联:

Kotlin

class TwoPaneOnBackPressedCallback(
    private val slidingPaneLayout: SlidingPaneLayout
) : OnBackPressedCallback(
    // Set the default 'enabled' state to true only if it is slidable, such as
    // when the panes overlap, and open, such as when the detail pane is
    // visible.
    slidingPaneLayout.isSlideable && slidingPaneLayout.isOpen
), SlidingPaneLayout.PanelSlideListener {

    init {
        slidingPaneLayout.addPanelSlideListener(this)
    }

    override fun handleOnBackPressed() {
        // Return to the list pane when the system back button is tapped.
        slidingPaneLayout.closePane()
    }

    override fun onPanelSlide(panel: View, slideOffset: Float) { }

    override fun onPanelOpened(panel: View) {
        // Intercept the system back button when the detail pane becomes
        // visible.
        isEnabled = true
    }

    override fun onPanelClosed(panel: View) {
        // Disable intercepting the system back button when the user returns to
        // the list pane.
        isEnabled = false
    }
}

Java

class TwoPaneOnBackPressedCallback extends OnBackPressedCallback
        implements SlidingPaneLayout.PanelSlideListener {

    private final SlidingPaneLayout mSlidingPaneLayout;

    TwoPaneOnBackPressedCallback(@NonNull SlidingPaneLayout slidingPaneLayout) {
        // Set the default 'enabled' state to true only if it is slideable, such
        // as when the panes overlap, and open, such as when the detail pane is
        // visible.
        super(slidingPaneLayout.isSlideable() && slidingPaneLayout.isOpen());
        mSlidingPaneLayout = slidingPaneLayout;
        slidingPaneLayout.addPanelSlideListener(this);
    }

    @Override
    public void handleOnBackPressed() {
        // Return to the list pane when the system back button is tapped.
        mSlidingPaneLayout.closePane();
    }

    @Override
    public void onPanelSlide(@NonNull View panel, float slideOffset) { }

    @Override
    public void onPanelOpened(@NonNull View panel) {
        // Intercept the system back button when the detail pane becomes
        // visible.
        setEnabled(true);
    }

    @Override
    public void onPanelClosed(@NonNull View panel) {
        // Disable intercepting the system back button when the user returns to
        // the list pane.
        setEnabled(false);
    }
}

您可以使用 addCallback() 将回调添加到 OnBackPressedDispatcher

Kotlin

class TwoPaneFragment : Fragment(R.layout.two_pane) {

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        val binding = TwoPaneBinding.bind(view)

        // Connect the SlidingPaneLayout to the system back button.
        requireActivity().onBackPressedDispatcher.addCallback(viewLifecycleOwner,
            TwoPaneOnBackPressedCallback(binding.slidingPaneLayout))

        // Set up the RecyclerView adapter.
    }
}

Java

class TwoPaneFragment extends Fragment {

    public TwoPaneFragment() {
        super(R.layout.two_pane);
    }

    @Override
    public void onViewCreated(@NonNull View view,
             @Nullable Bundle savedInstanceState) {
        TwoPaneBinding binding = TwoPaneBinding.bind(view);

        // Connect the SlidingPaneLayout to the system back button.
        requireActivity().getOnBackPressedDispatcher().addCallback(
            getViewLifecycleOwner(),
            new TwoPaneOnBackPressedCallback(binding.getSlidingPaneLayout()));

        // Set up the RecyclerView adapter.
    }
}

锁定模式

SlidingPaneLayout 始终允许您手动调用 open()close(),以在手机上的列表窗格和详情窗格之间切换。如果两个窗格均可见且未重叠,这些方法不会产生任何影响。

如果列表窗格和详细信息窗格重叠,那么在默认情况下,用户可以向两个方向滑动,这样一来,即使在没有使用手势导航的情况下,也可以随意在两个窗格之间切换。您可以设置 SlidingPaneLayout 的锁定模式来控制滑动方向:

Kotlin

binding.slidingPaneLayout.lockMode = SlidingPaneLayout.LOCK_MODE_LOCKED

Java

binding.getSlidingPaneLayout().setLockMode(SlidingPaneLayout.LOCK_MODE_LOCKED);

了解详情

如需详细了解如何针对不同外形规格设计布局,请参阅以下文档:

其他资源