应用中的每个屏幕都必须具备自适应能力,并能根据可用空间进行调整。
您可以使用
ConstraintLayout
,可让单窗格
方法可以扩展到多种尺寸,但对于较大的设备,
将布局布局到多个窗格中例如,您可能想在屏幕上显示
项目列表,位于所选项目的详细信息列表旁边。
通过
SlidingPaneLayout
组件支持在较大的设备上并排显示两个窗格,
同时自动进行调整,以便每次仅显示一个窗格。
手机等较小的设备
如需了解针对特定设备的指南,请参阅 屏幕兼容性概览。
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
提供水平双窗格布局,以在顶部使用
界面级别在这种布局中,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](https://developer.android.google.cn/static/images/ui/slidingpanelayout-example.png?authuser=9&hl=nb)
SlidingPaneLayout
。
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,如果测量列表窗格具有
最小尺寸为 200 dp,并且详情窗格需要 400 dp,则
SlidingPaneLayout
会自动并排显示两个窗格,只要它
宽度至少为 600 dp。
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。
如果视图不重叠,SlidingPaneLayout
支持使用布局
子视图上的 layout_weight
参数,用于定义如何划分剩余空间
。此参数仅与宽度相关。
屏幕上有空间来并排显示两个视图的可折叠设备
SlidingPaneLayout
会自动调整两个窗格的大小
定位在重叠的折叠边或合页的任意一侧。在本课中,
在这种情况下,设置的宽度会被视为每个
折叠功能的侧面如果没有足够的空间来存放
最小尺寸,SlidingPaneLayout
会切换回与视图重叠。
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
从初始 fragment 复制到详情窗格,以确保大屏幕用户
应用首次启动时,设备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
会在详细信息窗格中触发更改在使用 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(); }
具体而言,此代码不会调用
addToBackStack()
在FragmentTransaction
上发布。这样可避免在详细信息窗格中构建返回堆栈。
Navigation 组件实现
本页中的示例直接使用 SlidingPaneLayout
,您必须执行以下操作:
手动管理 fragment 事务。不过,
Navigation 组件提供了
通过双窗格布局
AbstractListDetailFragment
、
一个在后台使用 SlidingPaneLayout
管理列表的 API 类
和详细信息窗格
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>
实施
onCreateListPaneView()
和
onListPaneViewCreated()
,为您的列表窗格提供自定义视图。对于“详细信息”窗格
AbstractListDetailFragment
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(); }
详情窗格的导航图中的目的地不得出现在
任何外部的应用级导航图。不过,详情中的任何深层链接
窗格的导航图必须附加到托管
SlidingPaneLayout
。这有助于确保外部深层链接先导航到
前往 SlidingPaneLayout
目的地,然后前往正确详情
窗格目标位置。
请参阅 TwoPaneFragment 示例 ,了解如何使用 Navigation 组件实现双窗格布局。
与系统返回按钮集成
在列表窗格和详情窗格重叠的小屏幕设备上,请确保系统
返回按钮可让用户从详情窗格返回到列表窗格。建议做法
通过提供自定义返回
导航和连接
OnBackPressedCallback
至
SlidingPaneLayout
的当前状态:
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); } }
您可以将回调添加到
OnBackPressedDispatcher
使用
addCallback()
:
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()
并
close()
以便在手机上的列表窗格和详情窗格之间转换。这些方法没有任何
效果。
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: