Fix SearchScaffold navigation back arrow

The issue is when search mode is on, cannot click navigation back arrow
to close the search mode.

The issue is caused by when navigation back arrow is clicked, it dismiss
the input method, which will call onSearchQueryChange again to reset the
search query and re-enter the search mode.

Split the isSearchMode from searchQuery to fix this issue.

Fix: 272574692
Test: Manually with Settings
Test: Unit test
Change-Id: Id2bcc643c8c85e57a543221a6951b00c11ae955a

packages/SettingsLib/Spa/spa/src/com/android/settingslib/spa/widget/scaffold/SearchScaffold.kt

@@ -41,6 +41,7 @@ import androidx.compose.runtime.derivedStateOf
 import androidx.compose.runtime.getValue
 import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.remember
+import androidx.compose.runtime.saveable.rememberSaveable
 import androidx.compose.runtime.setValue
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.draw.alpha
@@ -72,6 +73,7 @@ fun SearchScaffold(
     actions: @Composable RowScope.() -> Unit = {},
     content: @Composable (bottomPadding: Dp, searchQuery: State<String>) -> Unit,
 ) {
+    var isSearchMode by rememberSaveable { mutableStateOf(false) }
     val viewModel: SearchScaffoldViewModel = viewModel()
 
     val scrollBehavior = TopAppBarDefaults.exitUntilCollapsedScrollBehavior()
@@ -82,8 +84,11 @@ fun SearchScaffold(
                 title = title,
                 actions = actions,
                 scrollBehavior = scrollBehavior,
+                isSearchMode = isSearchMode,
+                onSearchModeChange = { isSearchMode = it },
                 searchQuery = viewModel.searchQuery,
-            ) { viewModel.searchQuery = it }
+                onSearchQueryChange = { viewModel.searchQuery = it },
+            )
         },
     ) { paddingValues ->
         Box(
@@ -95,7 +100,7 @@ fun SearchScaffold(
             content(
                 bottomPadding = paddingValues.calculateBottomPadding(),
                 searchQuery = remember {
-                    derivedStateOf { viewModel.searchQuery?.text ?: "" }
+                    derivedStateOf { if (isSearchMode) viewModel.searchQuery.text else "" }
                 },
             )
         }
@@ -103,7 +108,8 @@ fun SearchScaffold(
 }
 
 internal class SearchScaffoldViewModel : ViewModel() {
-    var searchQuery: TextFieldValue? by mutableStateOf(null)
+    // Put in view model because TextFieldValue has not default Saver for rememberSaveable.
+    var searchQuery by mutableStateOf(TextFieldValue())
 }
 
 @OptIn(ExperimentalMaterial3Api::class)
@@ -112,14 +118,16 @@ private fun SearchableTopAppBar(
     title: String,
     actions: @Composable RowScope.() -> Unit,
     scrollBehavior: TopAppBarScrollBehavior,
-    searchQuery: TextFieldValue?,
-    onSearchQueryChange: (TextFieldValue?) -> Unit,
+    isSearchMode: Boolean,
+    onSearchModeChange: (Boolean) -> Unit,
+    searchQuery: TextFieldValue,
+    onSearchQueryChange: (TextFieldValue) -> Unit,
 ) {
-    if (searchQuery != null) {
+    if (isSearchMode) {
         SearchTopAppBar(
             query = searchQuery,
             onQueryChange = onSearchQueryChange,
-            onClose = { onSearchQueryChange(null) },
+            onClose = { onSearchModeChange(false) },
             actions = actions,
         )
     } else {
@@ -127,6 +135,7 @@ private fun SearchableTopAppBar(
             SearchAction {
                 scrollBehavior.collapse()
                 onSearchQueryChange(TextFieldValue())
+                onSearchModeChange(true)
             }
             actions()
         }