[webview_flutter] Re-land support v2 embedding support (#2209)

Author: Michael Klimushyn

packages/webview_flutter/CHANGELOG.md

@@ -1,3 +1,11 @@
+## 0.3.15+3
+
+* Re-land support for the v2 Android embedding. This correctly sets the minimum
+  SDK to the latest stable and avoid any compile errors. *WARNING:* the V2
+  embedding itself still requires the current Flutter master channel
+  (flutter/flutter@1d4d63a) for text input to work properly on all Android
+  versions.
+
 ## 0.3.15+2
 
 * Remove AndroidX warnings.

packages/webview_flutter/android/build.gradle

@@ -37,3 +37,28 @@ 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 = "1.1.1"
+                compileOnly "android.arch.lifecycle:common-java8:$lifecycle_version"
+                compileOnly "android.arch.lifecycle:runtime:$lifecycle_version"
+            }
+        }
+    }
+}

packages/webview_flutter/android/gradle.properties

@@ -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/FlutterCookieManager.java

@@ -36,7 +36,7 @@ public class FlutterWebView implements PlatformView, MethodCallHandler {
       BinaryMessenger messenger,
       int id,
       Map<String, Object> params,
-      final View containerView) {
+      View containerView) {
 
     DisplayListenerProxy displayListenerProxy = new DisplayListenerProxy();
     DisplayManager displayManager =
@@ -95,6 +95,26 @@ public void onInputConnectionLocked() {
     webView.lockInputConnection();
   }
 
+  // @Override
+  // This is overriding a method that hasn't rolled into stable Flutter yet. Including the
+  // annotation would cause compile time failures in versions of Flutter too old to include the new
+  // method. However leaving it raw like this means that the method will be ignored in old versions
+  // of Flutter but used as an override anyway wherever it's actually defined.
+  // TODO(mklim): Add the @Override annotation once stable passes v1.10.9.
+  public void onFlutterViewAttached(View flutterView) {
+    webView.setContainerView(flutterView);
+  }
+
+  // @Override
+  // This is overriding a method that hasn't rolled into stable Flutter yet. Including the
+  // annotation would cause compile time failures in versions of Flutter too old to include the new
+  // method. However leaving it raw like this means that the method will be ignored in old versions
+  // of Flutter but used as an override anyway wherever it's actually defined.
+  // TODO(mklim): Add the @Override annotation once stable passes v1.10.9.
+  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/FlutterWebView.java

@@ -11,7 +11,6 @@
 import android.webkit.WebResourceRequest;
 import android.webkit.WebView;
 import android.webkit.WebViewClient;
-import androidx.annotation.NonNull;
 import androidx.webkit.WebViewClientCompat;
 import io.flutter.plugin.common.MethodChannel;
 import java.util.HashMap;
@@ -124,8 +123,7 @@ public void onUnhandledKeyEvent(WebView view, KeyEvent event) {
   private WebViewClientCompat internalCreateWebViewClientCompat() {
     return new WebViewClientCompat() {
       @Override
-      public boolean shouldOverrideUrlLoading(
-          @NonNull WebView view, @NonNull WebResourceRequest request) {
+      public boolean shouldOverrideUrlLoading(WebView view, WebResourceRequest request) {
         return FlutterWebViewClient.this.shouldOverrideUrlLoading(view, request);
       }
 

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

@@ -7,6 +7,7 @@
 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;
@@ -22,16 +23,29 @@
  * <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 View containerView;
 
   InputAwareWebView(Context context, View containerView) {
     super(context);
     this.containerView = containerView;
   }
 
+  void setContainerView(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 +95,12 @@ 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 +140,10 @@ 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 +156,13 @@ 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/InputAwareWebView.java

@@ -4,17 +4,71 @@
 
 package io.flutter.plugins.webviewflutter;
 
+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 FlutterCookieManager flutterCookieManager;
+
+  /**
+   * Add an instance of this to {@link io.flutter.embedding.engine.plugins.PluginRegistry} to
+   * register it.
+   *
+   * <p>THIS PLUGIN CODE PATH DEPENDS ON A NEWER VERSION OF FLUTTER THAN THE ONE DEFINED IN THE
+   * PUBSPEC.YAML. Text input will fail on some Android devices unless this is used with at least
+   * flutter/flutter@1d4d63ace1f801a022ea9ec737bf8c15395588b9. Use the V1 embedding with {@link
+   * #registerWith(Registrar)} to use this plugin with older Flutter versions.
+   *
+   * <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(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(FlutterPluginBinding binding) {
+    if (flutterCookieManager == null) {
+      return;
+    }
+
+    flutterCookieManager.dispose();
+    flutterCookieManager = null;
   }
 }

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

@@ -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/build.gradle

@@ -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);
+}

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

@@ -0,0 +1,11 @@
+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 MainActivityTest {
+  @Rule public ActivityTestRule<MainActivity> rule = new ActivityTestRule<>(MainActivity.class);
+}