Make API for showing DialogNavigator destinations public

Previously, the only way to use DialogNavigator
via public APIs was directly through usage of NavHost.

By making the DialogNavigator->Dialog Composable
function public, DialogNavigator can be reused in
any custom NavHost without making its internal state
public.

Test: DialogNavigatorTest suite still passes
Relnote: N/A
Change-Id: I125838dc978ee014af46a264deb1458596cce691

navigation/navigation-compose/api/current.txt

@@ -10,6 +10,10 @@ package androidx.navigation.compose {
     ctor public ComposeNavigator.Destination(androidx.navigation.compose.ComposeNavigator navigator, kotlin.jvm.functions.Function1<? super androidx.navigation.NavBackStackEntry,kotlin.Unit> content);
   }
 
+  public final class DialogHostKt {
+    method @androidx.compose.runtime.Composable public static void DialogHost(androidx.navigation.compose.DialogNavigator dialogNavigator);
+  }
+
   @androidx.navigation.Navigator.Name("dialog") public final class DialogNavigator extends androidx.navigation.Navigator<androidx.navigation.compose.DialogNavigator.Destination> {
     ctor public DialogNavigator();
     method public androidx.navigation.compose.DialogNavigator.Destination createDestination();

navigation/navigation-compose/api/public_plus_experimental_current.txt

@@ -10,6 +10,10 @@ package androidx.navigation.compose {
     ctor public ComposeNavigator.Destination(androidx.navigation.compose.ComposeNavigator navigator, kotlin.jvm.functions.Function1<? super androidx.navigation.NavBackStackEntry,kotlin.Unit> content);
   }
 
+  public final class DialogHostKt {
+    method @androidx.compose.runtime.Composable public static void DialogHost(androidx.navigation.compose.DialogNavigator dialogNavigator);
+  }
+
   @androidx.navigation.Navigator.Name("dialog") public final class DialogNavigator extends androidx.navigation.Navigator<androidx.navigation.compose.DialogNavigator.Destination> {
     ctor public DialogNavigator();
     method public androidx.navigation.compose.DialogNavigator.Destination createDestination();

navigation/navigation-compose/api/restricted_current.txt

@@ -10,6 +10,10 @@ package androidx.navigation.compose {
     ctor public ComposeNavigator.Destination(androidx.navigation.compose.ComposeNavigator navigator, kotlin.jvm.functions.Function1<? super androidx.navigation.NavBackStackEntry,kotlin.Unit> content);
   }
 
+  public final class DialogHostKt {
+    method @androidx.compose.runtime.Composable public static void DialogHost(androidx.navigation.compose.DialogNavigator dialogNavigator);
+  }
+
   @androidx.navigation.Navigator.Name("dialog") public final class DialogNavigator extends androidx.navigation.Navigator<androidx.navigation.compose.DialogNavigator.Destination> {
     ctor public DialogNavigator();
     method public androidx.navigation.compose.DialogNavigator.Destination createDestination();

navigation/navigation-compose/src/androidTest/java/androidx/navigation/compose/DialogNavigatorTest.kt

@@ -42,7 +42,7 @@ class DialogNavigatorTest {
         navigator.onAttach(navigatorState)
 
         rule.setContent {
-            navigator.Dialogs()
+            DialogHost(navigator)
         }
 
         rule.onNodeWithText(defaultText).assertDoesNotExist()
@@ -68,7 +68,7 @@ class DialogNavigatorTest {
         navigator.navigate(listOf(entry), null, null)
 
         rule.setContent {
-            navigator.Dialogs()
+            DialogHost(navigator)
         }
 
         rule.onNodeWithText(defaultText).assertIsDisplayed()

navigation/navigation-compose/src/main/java/androidx/navigation/compose/DialogHost.kt

@@ -0,0 +1,52 @@
+/*
+ * Copyright 2021 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package androidx.navigation.compose
+
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.collectAsState
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.saveable.rememberSaveableStateHolder
+import androidx.compose.ui.window.Dialog
+import androidx.lifecycle.Lifecycle
+import androidx.navigation.compose.DialogNavigator.Destination
+
+/**
+ * Show each [Destination] on the [DialogNavigator]'s back stack as a [Dialog].
+ *
+ * Note that [NavHost] will call this for you; you do not need to call it manually.
+ */
+@Composable
+public fun DialogHost(dialogNavigator: DialogNavigator) {
+    val saveableStateHolder = rememberSaveableStateHolder()
+    val dialogBackStack by dialogNavigator.backStack.collectAsState()
+
+    dialogBackStack.filter { backStackEntry ->
+        backStackEntry.lifecycle.currentState.isAtLeast(Lifecycle.State.STARTED)
+    }.forEach { backStackEntry ->
+        val destination = backStackEntry.destination as Destination
+        Dialog(
+            onDismissRequest = { dialogNavigator.dismiss(backStackEntry) },
+            properties = destination.dialogProperties
+        ) {
+            // while in the scope of the composable, we provide the navBackStackEntry as the
+            // ViewModelStoreOwner and LifecycleOwner
+            backStackEntry.LocalOwnersProvider(saveableStateHolder) {
+                destination.content(backStackEntry)
+            }
+        }
+    }
+}

navigation/navigation-compose/src/main/java/androidx/navigation/compose/DialogNavigator.kt

@@ -17,14 +17,11 @@
 package androidx.navigation.compose
 
 import androidx.compose.runtime.Composable
-import androidx.compose.runtime.collectAsState
 import androidx.compose.runtime.getValue
 import androidx.compose.runtime.mutableStateOf
-import androidx.compose.runtime.saveable.rememberSaveableStateHolder
 import androidx.compose.runtime.setValue
 import androidx.compose.ui.window.Dialog
 import androidx.compose.ui.window.DialogProperties
-import androidx.lifecycle.Lifecycle
 import androidx.navigation.FloatingWindow
 import androidx.navigation.NavBackStackEntry
 import androidx.navigation.NavDestination
@@ -50,36 +47,20 @@ public class DialogNavigator : Navigator<Destination>() {
      * the Navigator is attached, so we specifically return an empty flow if we
      * aren't attached yet.
      */
-    private val backStack: StateFlow<List<NavBackStackEntry>> get() = if (attached) {
+    internal val backStack: StateFlow<List<NavBackStackEntry>> get() = if (attached) {
         state.backStack
     } else {
         MutableStateFlow(emptyList())
     }
 
     /**
-     * Show each [Destination] on the back stack as a [Dialog].
-     *
-     * Note that [NavHost] will call this for you; you do not need to call it manually.
+     * Dismiss the dialog destination associated with the given [backStackEntry].
      */
-    internal val Dialogs: @Composable () -> Unit = @Composable {
-        val saveableStateHolder = rememberSaveableStateHolder()
-        val dialogBackStack by backStack.collectAsState()
-
-        dialogBackStack.filter { backStackEntry ->
-            backStackEntry.lifecycle.currentState.isAtLeast(Lifecycle.State.STARTED)
-        }.forEach { backStackEntry ->
-            val destination = backStackEntry.destination as Destination
-            Dialog(
-                onDismissRequest = { state.pop(backStackEntry, false) },
-                properties = destination.dialogProperties
-            ) {
-                // while in the scope of the composable, we provide the navBackStackEntry as the
-                // ViewModelStoreOwner and LifecycleOwner
-                backStackEntry.LocalOwnersProvider(saveableStateHolder) {
-                    destination.content(backStackEntry)
-                }
-            }
+    internal fun dismiss(backStackEntry: NavBackStackEntry) {
+        check(attached) {
+            "The DialogNavigator must be attached to a NavController to call dismiss"
         }
+        state.pop(backStackEntry, false)
     }
 
     override fun onAttach(state: NavigatorState) {

navigation/navigation-compose/src/main/java/androidx/navigation/compose/NavHost.kt

@@ -141,5 +141,5 @@ public fun NavHost(
     ) as? DialogNavigator ?: return
 
     // Show any dialog destinations
-    dialogNavigator.Dialogs()
+    DialogHost(dialogNavigator)
 }