如何修复展开的material3 SearchBar的onBackPressed？

Question

我在 Android 项目中使用处于

expanded

状态的 androidx.compose.material3.SearchBar。我正在使用

androidx.compose:compose-bom:2024.09.02

，其中包括

androidx.compose.material3:material3-*:1.3.0

。

屏幕截图显示了用户执行 back 手势时发生的情况。

以下是相关类和文件的结构：

搜索活动.kt：

class SearchActivity {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_search)
        if (savedInstanceState == null) {
            addFragment(R.id.container, SearchFragment(), SearchFragment.FRAGMENT_TAG)
        }
    }
}

布局/activity_search.xml：

<androidx.constraintlayout.widget.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <androidx.fragment.app.FragmentContainerView
        android:id="@+id/container"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        tools:context=".search.SearchActivity"
        tools:ignore="MergeRootFrame"
        tools:layout="@layout/fragment_search" />

</androidx.constraintlayout.widget.ConstraintLayout>

SearchFragment.kt：

class SearchFragment : Fragment() {

    companion object {
        const val FRAGMENT_TAG = "SEARCH_FRAGMENT_TAG"

        fun replaceAtBackStack(fragmentManager: FragmentManager, @IdRes containerViewId: Int) {
            fragmentManager.commit {
                fragmentManager.popBackStack(FRAGMENT_TAG, FragmentManager.POP_BACK_STACK_INCLUSIVE)
                fragmentManager.replaceFragment(containerViewId, SearchFragment(), FRAGMENT_TAG, FRAGMENT_TAG)
            }
        }
    }

    private val viewModelFactory by lazy { SearchViewModelFactory(/*...*/) }
    private val viewModel: SearchViewModel by viewModels { viewModelFactory }

    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View = 
      inflater.inflate(R.layout.fragment_search, container, false).apply {
        findViewById<ComposeView>(R.id.search_view).apply {
            setViewCompositionStrategy(DisposeOnViewTreeLifecycleDestroyed)
            setContent {
                SearchScreen(
                    searchQuery = viewModel.searchQuery,
                    state = viewModel.searchResultsState.collectAsState().value,
                    onViewEvent = viewModel::onViewEvent,
                )
            }
            isClickable = true
        }
    }

}

布局/fragment_search.xml：

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 
    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.compose.ui.platform.ComposeView
        android:id="@+id/search_view"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

SearchScreen.kt：

@OptIn(ExperimentalMaterial3Api::class)
@Composable
fun SearchScreen(
    searchQuery: String,
    state: SearchResultState,
    onViewEvent: (SearchViewEvent) -> Unit,
) {
    MyTheme {
        Scaffold { contentPadding ->
            Box(
                Modifier
                    .padding(contentPadding)
            ) {
                var text by rememberSaveable { mutableStateOf(searchQuery) }
                val expanded = true
                SearchBar(
                    modifier = Modifier
                        .align(TopCenter)
                        .semantics { traversalIndex = 0f },
                    inputField = {
                        SearchBarDefaults.InputField(
                            query = text,
                            onQueryChange = {
                                text = it
                                onViewEvent(OnSearchQueryChange(it))
                            },
                            onSearch = { },
                            expanded = expanded,
                            onExpandedChange = { },
                            placeholder = { Text(stringResource(R.string.search_query_hint)) },
                            leadingIcon = { Icon(Icons.Default.Search, contentDescription = null) },
                        )
                    },
                    expanded = expanded,
                    onExpandedChange = { }
                ) {
                    when (state) {
                        is Loading -> Loading()
                        is Success -> {
                            val sessions = state.parameters
                            if (sessions.isEmpty()) {
                                NoSearchResult()
                            } else {
                                SearchResultList(
                                    parameters = sessions,
                                    onViewEvent = onViewEvent,
                                )
                            }
                        }
                    }
                }
            }
        }
    }
}

由于某种原因，

SearchBar

消耗了后退手势。 - 当我用其他一些简单的可组合项替换

SearchBar

时，我注意到了这一点。 - 这可以防止用户完全离开屏幕，这正是我期望在 back 手势上发生的情况。
如何解决这个问题？

Answer 1

我缺少一个

androidx.activity.compose.BackHandler

，可在

androidx.activity:activity-compose

中找到。添加依赖项后，您可以将

BackHandler

添加到可组合项中：

SearchScreen.kt：

@OptIn(ExperimentalMaterial3Api::class)
@Composable
fun SearchScreen(
    searchQuery: String,
    state: SearchResultState,
    onViewEvent: (SearchViewEvent) -> Unit,
) {
    MyTheme {
        Scaffold { contentPadding ->
            Box(
                Modifier
                    .padding(contentPadding)
            ) {
                var text by rememberSaveable { mutableStateOf(searchQuery) }
                val expanded = true
                SearchBar(
                    modifier = Modifier
                        .align(TopCenter)
                        .semantics { traversalIndex = 0f },
                    inputField = { /*...*/ }
                }
                BackHandler {
                    onViewEvent(OnBackPress)
                }
            }
        }
    }
}

...然后将其传递到视图模型并在片段中从后台堆栈中弹出它并完成托管活动:

SearchFragment.kt：

class SearchFragment : Fragment() {

    companion object {
        const val FRAGMENT_TAG = "SEARCH_FRAGMENT_TAG"

        fun replaceAtBackStack(fragmentManager: FragmentManager, @IdRes containerViewId: Int) {
            fragmentManager.commit {
                fragmentManager.popBackStack(FRAGMENT_TAG, FragmentManager.POP_BACK_STACK_INCLUSIVE)
                fragmentManager.replaceFragment(containerViewId, SearchFragment(), FRAGMENT_TAG, FRAGMENT_TAG)
            }
        }
    }

    private val viewModelFactory by lazy { SearchViewModelFactory(/*...*/) }
    private val viewModel: SearchViewModel by viewModels { viewModelFactory }

    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View = 
      inflater.inflate(R.layout.fragment_search, container, false).apply {
        findViewById<ComposeView>(R.id.search_view).apply {
            setViewCompositionStrategy(DisposeOnViewTreeLifecycleDestroyed)
            setContent {
                SearchScreen(
                    searchQuery = viewModel.searchQuery,
                    state = viewModel.searchResultsState.collectAsState().value,
                    onViewEvent = viewModel::onViewEvent,
                )
            }
            isClickable = true
        }
    }

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        observeViewModel()
    }

    private fun observeViewModel() {
        viewModel.navigateBack.observe(viewLifecycleOwner) {
            parentFragmentManager.popBackStack(FRAGMENT_TAG, FragmentManager.POP_BACK_STACK_INCLUSIVE)
            requireActivity().finish()
        }
    }
}