[flutter_webview] Migrate to the new embedding (#2169)

This depends on a new bugfix on the engine for text input to work with
the new embedding (flutter/engine#13015).

Author: Michael Klimushyn

packages/webview_flutter/CHANGELOG.md

@@ -1,3 +1,9 @@
+## 0.3.15
+
+* Add support for the v2 Android embedding. This shouldn't affect existing
+  functionality. Plugin authors who use the V2 embedding can now register the
+  plugin and expect that it correctly responds to app lifecycle changes.
+
 ## 0.3.14+2
 
 * Define clang module for iOS.
@@ -13,7 +19,7 @@
 ## 0.3.13
 
 * Add an optional `userAgent` property to set a custom User Agent.
-  
+
 ## 0.3.12+1
 
 * Temporarily revert getTitle (doing this as a patch bump shortly after publishing).

packages/webview_flutter/android/build.gradle

@@ -50,3 +50,28 @@ android {
         implementation 'androidx.webkit:webkit:1.0.0'
     }
 }
+
+// TODO(mklim): Remove this hack once androidx.lifecycle is included on stable. https://github.com/flutter/flutter/issues/42348
+afterEvaluate {
+    def containsEmbeddingDependencies = false
+    for (def configuration : configurations.all) {
+        for (def dependency : configuration.dependencies) {
+            if (dependency.group == 'io.flutter' &&
+                dependency.name.startsWith('flutter_embedding') &&
+                dependency.isTransitive())
+            {
+                containsEmbeddingDependencies = true
+                break
+            }
+        }
+    }
+    if (!containsEmbeddingDependencies) {
+        android {
+            dependencies {
+                def lifecycle_version = "2.1.0"
+                api "androidx.lifecycle:lifecycle-common-java8:$lifecycle_version"
+                api "androidx.lifecycle:lifecycle-runtime:$lifecycle_version"
+            }
+        }
+    }
+}

packages/webview_flutter/android/gradle.properties

@@ -1 +1,3 @@
 org.gradle.jvmargs=-Xmx1536M
+android.enableJetifier=true
+android.useAndroidX=true

packages/webview_flutter/android/src/main/java/io/flutter/plugins/webviewflutter/FlutterCookieManager.java

@@ -15,17 +15,11 @@
 import io.flutter.plugin.common.MethodChannel.Result;
 
 class FlutterCookieManager implements MethodCallHandler {
+  private final MethodChannel methodChannel;
 
-  private FlutterCookieManager() {
-    // Do not instantiate.
-    // This class should only be used in context of a BinaryMessenger.
-    // Use FlutterCookieManager#registerWith instead.
-  }
-
-  static void registerWith(BinaryMessenger messenger) {
-    MethodChannel methodChannel = new MethodChannel(messenger, "plugins.flutter.io/cookie_manager");
-    FlutterCookieManager cookieManager = new FlutterCookieManager();
-    methodChannel.setMethodCallHandler(cookieManager);
+  FlutterCookieManager(BinaryMessenger messenger) {
+    methodChannel = new MethodChannel(messenger, "plugins.flutter.io/cookie_manager");
+    methodChannel.setMethodCallHandler(this);
   }
 
   @Override
@@ -39,6 +33,10 @@ public void onMethodCall(MethodCall methodCall, Result result) {
     }
   }
 
+  void dispose() {
+    methodChannel.setMethodCallHandler(null);
+  }
+
   private static void clearCookies(final Result result) {
     CookieManager cookieManager = CookieManager.getInstance();
     final boolean hasCookies = cookieManager.hasCookies();

packages/webview_flutter/android/src/main/java/io/flutter/plugins/webviewflutter/FlutterWebView.java

@@ -12,6 +12,8 @@
 import android.view.View;
 import android.webkit.WebStorage;
 import android.webkit.WebViewClient;
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
 import io.flutter.plugin.common.BinaryMessenger;
 import io.flutter.plugin.common.MethodCall;
 import io.flutter.plugin.common.MethodChannel;
@@ -36,7 +38,7 @@ public class FlutterWebView implements PlatformView, MethodCallHandler {
       BinaryMessenger messenger,
       int id,
       Map<String, Object> params,
-      final View containerView) {
+      @Nullable View containerView) {
 
     DisplayListenerProxy displayListenerProxy = new DisplayListenerProxy();
     DisplayManager displayManager =
@@ -95,6 +97,16 @@ public void onInputConnectionLocked() {
     webView.lockInputConnection();
   }
 
+  @Override
+  public void onFlutterViewAttached(@NonNull View flutterView) {
+    webView.setContainerView(flutterView);
+  }
+
+  @Override
+  public void onFlutterViewDetached() {
+    webView.setContainerView(null);
+  }
+
   @Override
   public void onMethodCall(MethodCall methodCall, Result result) {
     switch (methodCall.method) {

packages/webview_flutter/android/src/main/java/io/flutter/plugins/webviewflutter/InputAwareWebView.java

@@ -7,9 +7,11 @@
 import static android.content.Context.INPUT_METHOD_SERVICE;
 
 import android.content.Context;
+import android.util.Log;
 import android.view.View;
 import android.view.inputmethod.InputMethodManager;
 import android.webkit.WebView;
+import androidx.annotation.Nullable;
 
 /**
  * A WebView subclass that mirrors the same implementation hacks that the system WebView does in
@@ -22,16 +24,29 @@
  * <p>See also {@link ThreadedInputConnectionProxyAdapterView}.
  */
 final class InputAwareWebView extends WebView {
-  private final View containerView;
-
+  private static final String TAG = "InputAwareWebView";
   private View threadedInputConnectionProxyView;
   private ThreadedInputConnectionProxyAdapterView proxyAdapterView;
+  private @Nullable View containerView;
 
-  InputAwareWebView(Context context, View containerView) {
+  InputAwareWebView(Context context, @Nullable View containerView) {
     super(context);
     this.containerView = containerView;
   }
 
+  void setContainerView(@Nullable View containerView) {
+    this.containerView = containerView;
+
+    if (proxyAdapterView == null) {
+      return;
+    }
+
+    Log.w(TAG, "The containerView has changed while the proxyAdapterView exists.");
+    if (containerView != null) {
+      setInputConnectionTarget(proxyAdapterView);
+    }
+  }
+
   /**
    * Set our proxy adapter view to use its cached input connection instead of creating new ones.
    *
@@ -81,6 +96,12 @@ public boolean checkInputConnectionProxy(final View view) {
       // This isn't a new ThreadedInputConnectionProxyView. Ignore it.
       return super.checkInputConnectionProxy(view);
     }
+    if (containerView == null) {
+      Log.e(
+          TAG,
+          "Can't create a proxy view because there's no container view. Text input may not work.");
+      return super.checkInputConnectionProxy(view);
+    }
 
     // We've never seen this before, so we make the assumption that this is WebView's
     // ThreadedInputConnectionProxyView. We are making the assumption that the only view that could
@@ -120,6 +141,10 @@ private void resetInputConnection() {
       // No need to reset the InputConnection to the default thread if we've never changed it.
       return;
     }
+    if (containerView == null) {
+      Log.e(TAG, "Can't reset the input connection to the container view because there is none.");
+      return;
+    }
     setInputConnectionTarget(/*targetView=*/ containerView);
   }
 
@@ -132,6 +157,13 @@ private void resetInputConnection() {
    * InputConnections should be created on.
    */
   private void setInputConnectionTarget(final View targetView) {
+    if (containerView == null) {
+      Log.e(
+          TAG,
+          "Can't set the input connection target because there is no containerView to use as a handler.");
+      return;
+    }
+
     targetView.requestFocus();
     containerView.post(
         new Runnable() {

packages/webview_flutter/android/src/main/java/io/flutter/plugins/webviewflutter/WebViewFactory.java

@@ -6,6 +6,7 @@
 
 import android.content.Context;
 import android.view.View;
+import androidx.annotation.Nullable;
 import io.flutter.plugin.common.BinaryMessenger;
 import io.flutter.plugin.common.StandardMessageCodec;
 import io.flutter.plugin.platform.PlatformView;
@@ -14,9 +15,9 @@
 
 public final class WebViewFactory extends PlatformViewFactory {
   private final BinaryMessenger messenger;
-  private final View containerView;
+  private @Nullable final View containerView;
 
-  WebViewFactory(BinaryMessenger messenger, View containerView) {
+  WebViewFactory(BinaryMessenger messenger, @Nullable View containerView) {
     super(StandardMessageCodec.INSTANCE);
     this.messenger = messenger;
     this.containerView = containerView;

packages/webview_flutter/android/src/main/java/io/flutter/plugins/webviewflutter/WebViewFlutterPlugin.java

@@ -4,17 +4,68 @@
 
 package io.flutter.plugins.webviewflutter;
 
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+import io.flutter.embedding.engine.plugins.FlutterPlugin;
+import io.flutter.plugin.common.BinaryMessenger;
 import io.flutter.plugin.common.PluginRegistry.Registrar;
 
-/** WebViewFlutterPlugin */
-public class WebViewFlutterPlugin {
-  /** Plugin registration. */
+/**
+ * Java platform implementation of the webview_flutter plugin.
+ *
+ * <p>Register this in an add to app scenario to gracefully handle activity and context changes.
+ *
+ * <p>Call {@link #registerWith(Registrar)} to use the stable {@code io.flutter.plugin.common}
+ * package instead.
+ */
+public class WebViewFlutterPlugin implements FlutterPlugin {
+
+  private @Nullable FlutterCookieManager flutterCookieManager;
+
+  /**
+   * Add an instance of this to {@link io.flutter.embedding.engine.plugins.PluginRegistry} to
+   * register it.
+   *
+   * <p>Registration should eventually be handled automatically by v2 of the
+   * GeneratedPluginRegistrant. https://github.com/flutter/flutter/issues/42694
+   */
+  public WebViewFlutterPlugin() {}
+
+  /**
+   * Registers a plugin implementation that uses the stable {@code io.flutter.plugin.common}
+   * package.
+   *
+   * <p>Calling this automatically initializes the plugin. However plugins initialized this way
+   * won't react to changes in activity or context, unlike {@link CameraPlugin}.
+   */
   public static void registerWith(Registrar registrar) {
     registrar
         .platformViewRegistry()
         .registerViewFactory(
             "plugins.flutter.io/webview",
             new WebViewFactory(registrar.messenger(), registrar.view()));
-    FlutterCookieManager.registerWith(registrar.messenger());
+    new FlutterCookieManager(registrar.messenger());
+  }
+
+  @Override
+  public void onAttachedToEngine(@NonNull FlutterPluginBinding binding) {
+    BinaryMessenger messenger = binding.getFlutterEngine().getDartExecutor();
+    binding
+        .getFlutterEngine()
+        .getPlatformViewsController()
+        .getRegistry()
+        .registerViewFactory(
+            "plugins.flutter.io/webview", new WebViewFactory(messenger, /*containerView=*/ null));
+    flutterCookieManager = new FlutterCookieManager(messenger);
+  }
+
+  @Override
+  public void onDetachedFromEngine(@NonNull FlutterPluginBinding binding) {
+    if (flutterCookieManager == null) {
+      return;
+    }
+
+    flutterCookieManager.dispose();
+    flutterCookieManager = null;
   }
 }

packages/webview_flutter/example/android/app/build.gradle

@@ -56,6 +56,7 @@ flutter {
 
 dependencies {
     testImplementation 'junit:junit:4.12'
-    androidTestImplementation 'androidx.test:runner:1.1.1'
-    androidTestImplementation 'androidx.test.espresso:espresso-core:3.1.1'
+    androidTestImplementation 'androidx.test:runner:1.2.0'
+    androidTestImplementation 'androidx.test:rules:1.2.0'
+    androidTestImplementation 'androidx.test.espresso:espresso-core:3.2.0'
 }

packages/webview_flutter/example/android/app/src/androidTestDebug/java/io/flutter/plugins/webviewflutterexample/EmbeddingV1ActivityTest.java

@@ -0,0 +1,13 @@
+package io.flutter.plugins.webviewflutterexample;
+
+import androidx.test.rule.ActivityTestRule;
+import dev.flutter.plugins.e2e.FlutterRunner;
+import org.junit.Rule;
+import org.junit.runner.RunWith;
+
+@RunWith(FlutterRunner.class)
+public class EmbeddingV1ActivityTest {
+  @Rule
+  public ActivityTestRule<EmbeddingV1Activity> rule =
+      new ActivityTestRule<>(EmbeddingV1Activity.class);
+}