Support a model where the application creates a FlutterNativeView tha…

…t is never destroyed (flutter#5256) This allows applications to start a Flutter engine instance during app startup and keep it running throughout the app process' lifetime. FlutterActivity subclasses can override createFlutterNativeView to provide a preinitialized FlutterNativeView instance and override retainFlutterNativeView to signal that the FlutterNativeView should be kept alive when the activity is destroyed.
aam · May 15, 2018 · c7ab033 · c7ab033
1 parent e463e80
commit c7ab033
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Showing 4 changed files with 41 additions and 4 deletions.
diff --git a/shell/platform/android/io/flutter/app/FlutterActivity.java b/shell/platform/android/io/flutter/app/FlutterActivity.java
@@ -60,6 +60,11 @@ public FlutterNativeView createFlutterNativeView() {
         return null;
     }
 
+    @Override
+    public boolean retainFlutterNativeView() {
+        return false;
+    }
+
     @Override
     public final boolean hasPlugin(String key) {
         return pluginRegistry.hasPlugin(key);

diff --git a/shell/platform/android/io/flutter/app/FlutterActivityDelegate.java b/shell/platform/android/io/flutter/app/FlutterActivityDelegate.java
@@ -85,6 +85,13 @@ public final class FlutterActivityDelegate
     public interface ViewFactory {
         FlutterView createFlutterView(Context context);
         FlutterNativeView createFlutterNativeView();
+
+        /**
+         * Hook for subclasses to indicate that the {@code FlutterNativeView}
+         * returned by {@link #createFlutterNativeView()} should not be destroyed
+         * when this activity is destroyed.
+         */
+        boolean retainFlutterNativeView();
     }
 
     private final Activity activity;
@@ -172,9 +179,11 @@ public void onCreate(Bundle savedInstanceState) {
         if (loadIntent(activity.getIntent(), reuseIsolate)) {
             return;
         }
-        String appBundlePath = FlutterMain.findAppBundlePath(activity.getApplicationContext());
-        if (appBundlePath != null) {
+        if (!flutterView.getFlutterNativeView().isApplicationRunning()) {
+          String appBundlePath = FlutterMain.findAppBundlePath(activity.getApplicationContext());
+          if (appBundlePath != null) {
             flutterView.runFromBundle(appBundlePath, null, "main", reuseIsolate);
+          }
         }
     }
 
@@ -250,7 +259,7 @@ public void onDestroy() {
         if (flutterView != null) {
             final boolean detach =
                 flutterView.getPluginRegistry().onViewDestroy(flutterView.getFlutterNativeView());
-            if (detach) {
+            if (detach || viewFactory.retainFlutterNativeView()) {
                 // Detach, but do not destroy the FlutterView if a plugin
                 // expressed interest in its FlutterNativeView.
                 flutterView.detach();
@@ -343,7 +352,9 @@ private boolean loadIntent(Intent intent, boolean reuseIsolate) {
             if (route != null) {
                 flutterView.setInitialRoute(route);
             }
-            flutterView.runFromBundle(appBundlePath, intent.getStringExtra("snapshot"), "main", reuseIsolate);
+            if (!flutterView.getFlutterNativeView().isApplicationRunning()) {
+                flutterView.runFromBundle(appBundlePath, intent.getStringExtra("snapshot"), "main", reuseIsolate);
+            }
             return true;
         }
 

diff --git a/shell/platform/android/io/flutter/app/FlutterFragmentActivity.java b/shell/platform/android/io/flutter/app/FlutterFragmentActivity.java
@@ -64,6 +64,11 @@ public FlutterNativeView createFlutterNativeView() {
         return null;
     }
 
+    @Override
+    public boolean retainFlutterNativeView() {
+        return false;
+    }
+
     @Override
     public final boolean hasPlugin(String key) {
         return pluginRegistry.hasPlugin(key);

diff --git a/shell/platform/android/io/flutter/view/FlutterNativeView.java b/shell/platform/android/io/flutter/view/FlutterNativeView.java
@@ -26,6 +26,7 @@ public class FlutterNativeView implements BinaryMessenger {
     private long mNativePlatformView;
     private FlutterView mFlutterView;
     private final Context mContext;
+    private boolean applicationIsRunning;
 
     public FlutterNativeView(Context context) {
         mContext = context;
@@ -45,6 +46,7 @@ public void destroy() {
         mFlutterView = null;
         nativeDestroy(mNativePlatformView);
         mNativePlatformView = 0;
+        applicationIsRunning = false;
     }
 
     public FlutterPluginRegistry getPluginRegistry() {
@@ -71,12 +73,26 @@ public void assertAttached() {
 
     public void runFromBundle(String bundlePath, String snapshotOverride, String entrypoint, boolean reuseRuntimeController) {
         assertAttached();
+        if (applicationIsRunning)
+            throw new AssertionError("This Flutter engine instance is already running an application");
+
         nativeRunBundleAndSnapshot(mNativePlatformView, bundlePath, snapshotOverride, entrypoint, reuseRuntimeController, mContext.getResources().getAssets());
+
+        applicationIsRunning = true;
     }
 
     public void runFromSource(final String assetsDirectory, final String main, final String packages) {
         assertAttached();
+        if (applicationIsRunning)
+            throw new AssertionError("This Flutter engine instance is already running an application");
+
         nativeRunBundleAndSource(mNativePlatformView, assetsDirectory, main, packages);
+
+        applicationIsRunning = true;
+    }
+
+    public boolean isApplicationRunning() {
+      return applicationIsRunning;
     }
 
     public void setAssetBundlePathOnUI(final String assetsDirectory) {