构建辅助窗格布局

辅助窗格规范布局可将用户的注意力集中在应用的主要内容上，同时显示相关的辅助内容。例如，主 内容窗格可能会显示有关近期电影的信息，同时 窗格，其中会列出具有类似或相同主题的其他电影。 导演或主演。如需详细了解辅助窗格规范布局，请参阅 Material 3 辅助窗格指南。

实现辅助窗格

SupportingPaneScaffold 最多由三个窗格组成：一个主要窗格、一个辅助窗格和一个可选的额外窗格。该框架会处理将窗口空间分配给三个窗格的所有计算。已开启 大屏幕时，Scaffold 会显示主窗格，同时打开辅助窗格 。在小屏幕上，框架会全屏显示主窗格或辅助窗格。

图 1. 辅助窗格布局。

添加依赖项

SupportingPaneScaffold 是 Material 3 自适应布局库的一部分。

将以下三个相关的依赖项添加到 build.gradle 应用或模块：

Kotlin

implementation("androidx.compose.material3.adaptive:adaptive")
implementation("androidx.compose.material3.adaptive:adaptive-layout")
implementation("androidx.compose.material3.adaptive:adaptive-navigation")

Groovy

implementation 'androidx.compose.material3.adaptive:adaptive'
implementation 'androidx.compose.material3.adaptive:adaptive-layout'
implementation 'androidx.compose.material3.adaptive:adaptive-navigation'

• 自适应 - 低层级构建块，例如 HingeInfo和Posture
• adaptive-layout - 自适应布局，例如 SupportingPaneScaffold
• adaptive-navigation - 用于在和 在窗格之间

创建导航器和基架

在小窗口中，一次只能显示一个窗格，因此请使用 ThreePaneScaffoldNavigator（用于移入/移出） 窗格。使用以下代码创建导航器实例： rememberSupportingPaneScaffoldNavigator。 要处理返回手势，请使用 BackHandler，用于检查 canNavigateBack() 和通话 navigateBack()：

val navigator = rememberSupportingPaneScaffoldNavigator()

BackHandler(navigator.canNavigateBack()) {
    navigator.navigateBack()
}
SampleSupportingPaneScaffold.kt

基架需要 PaneScaffoldDirective， 控制如何拆分屏幕以及使用的间距； ThreePaneScaffoldValue，用于提供当前的 窗格的状态（例如，是展开还是隐藏）。对于默认 行为，请使用导航器的 scaffoldDirective 和 scaffoldValue：

SupportingPaneScaffold(
    directive = navigator.scaffoldDirective,
    value = navigator.scaffoldValue,
    mainPane = { /*...*/ },
    supportingPane = { /*...*/ },
)
SampleSupportingPaneScaffold.kt

主窗格和辅助窗格是包含内容的可组合项。使用 AnimatedPane 在导航期间应用默认窗格动画。使用 Scaffold 值检查辅助窗格是否 已隐藏；如果是，则显示一个按钮 navigateTo(ThreePaneScaffoldRole.Secondary)，用于显示 辅助窗格

下面是该架构的完整实现：

val navigator = rememberSupportingPaneScaffoldNavigator()

BackHandler(navigator.canNavigateBack()) {
    navigator.navigateBack()
}

SupportingPaneScaffold(
    directive = navigator.scaffoldDirective,
    value = navigator.scaffoldValue,
    mainPane = {
        AnimatedPane(modifier = Modifier.safeContentPadding()) {
            // Main pane content
            if (navigator.scaffoldValue[SupportingPaneScaffoldRole.Supporting] == PaneAdaptedValue.Hidden) {
                Button(
                    modifier = Modifier.wrapContentSize(),
                    onClick = {
                        navigator.navigateTo(SupportingPaneScaffoldRole.Supporting)
                    }
                ) {
                    Text("Show supporting pane")
                }
            } else {
                Text("Supporting pane is shown")
            }
        }
    },
    supportingPane = {
        AnimatedPane(modifier = Modifier.safeContentPadding()) {
            // Supporting pane content
            Text("Supporting pane")
        }
    },
)
SampleSupportingPaneScaffold.kt

提取窗格可组合项

将 SupportingPaneScaffold 的各个窗格提取到它们自己的窗格中 使它们可重复使用且可测试。使用 ThreePaneScaffoldScope，用于在以下情况下访问AnimatedPane： 您想要默认动画：

@Composable
fun ThreePaneScaffoldScope.MainPane(
    shouldShowSupportingPaneButton: Boolean,
    onNavigateToSupportingPane: () -> Unit,
    modifier: Modifier = Modifier,
) {
    AnimatedPane(modifier = modifier.safeContentPadding()) {
        // Main pane content
        if (shouldShowSupportingPaneButton) {
            Button(onClick = onNavigateToSupportingPane) {
                Text("Show supporting pane")
            }
        } else {
            Text("Supporting pane is shown")
        }
    }
}

@Composable
fun ThreePaneScaffoldScope.SupportingPane(
    modifier: Modifier = Modifier,
) {
    AnimatedPane(modifier = modifier.safeContentPadding()) {
        // Supporting pane content
        Text("This is the supporting pane")
    }
}
SampleSupportingPaneScaffold.kt

将窗格提取到可组合项中可以简化 SupportingPaneScaffold（将以下内容与完整实现进行比较 中 Scaffold 的相应值）：

val navigator = rememberSupportingPaneScaffoldNavigator()

BackHandler(navigator.canNavigateBack()) {
    navigator.navigateBack()
}

SupportingPaneScaffold(
    directive = navigator.scaffoldDirective,
    value = navigator.scaffoldValue,
    mainPane = {
        MainPane(
            shouldShowSupportingPaneButton = navigator.scaffoldValue.secondary == PaneAdaptedValue.Hidden,
            onNavigateToSupportingPane = { navigator.navigateTo(ThreePaneScaffoldRole.Secondary) }
        )
    },
    supportingPane = { SupportingPane() },
)
SampleSupportingPaneScaffold.kt