Complete routing for Java-to-Dart messages (#3140)

This patch completes the routing for Java-to-Dart platform messages.

shell/platform/android/io/flutter/view/FlutterView.java

@@ -581,11 +581,16 @@ public class FlutterView extends SurfaceView
     private static native void nativeSurfaceDestroyed(long nativePlatformViewAndroid);
     private static native Bitmap nativeGetBitmap(long nativePlatformViewAndroid);
 
+    // Send a platform message to Dart.
+    private static native void nativeDispatchPlatformMessage(long nativePlatformViewAndroid, String name, String message, int responseId);
     private static native void nativeDispatchPointerDataPacket(long nativePlatformViewAndroid, ByteBuffer buffer, int position);
     private static native void nativeDispatchSemanticsAction(long nativePlatformViewAndroid, int id, int action);
     private static native void nativeSetSemanticsEnabled(long nativePlatformViewAndroid, boolean enabled);
-    private static native void nativeInvokePlatformMessageResponseCallback(long nativePlatformViewAndroid, int responseId, String buffer);
 
+    // Send a response to a platform message received from Dart.
+    private static native void nativeInvokePlatformMessageResponseCallback(long nativePlatformViewAndroid, int responseId, String message);
+
+    // Called by native to send us a platform message.
     @CalledByNative
     private void handlePlatformMessage(String name, String message, final int responseId) {
         OnMessageListener listener = mOnMessageListeners.get(name);
@@ -597,10 +602,10 @@ public class FlutterView extends SurfaceView
         OnMessageListenerAsync asyncListener = mAsyncOnMessageListeners.get(name);
         if (asyncListener != null) {
             asyncListener.onMessage(this, message, new MessageResponse() {
-              @Override
-              public void send(String response) {
-                  nativeInvokePlatformMessageResponseCallback(mNativePlatformView, responseId, response);
-              }
+                @Override
+                public void send(String response) {
+                    nativeInvokePlatformMessageResponseCallback(mNativePlatformView, responseId, response);
+                }
             });
             return;
         }
@@ -608,6 +613,17 @@ public class FlutterView extends SurfaceView
         nativeInvokePlatformMessageResponseCallback(mNativePlatformView, responseId, null);
     }
 
+    private int mNextResponseId = 1;
+    private final Map<Integer, MessageReplyCallback> mPendingResponses = new HashMap<Integer, MessageReplyCallback>();
+
+    // Called by native to respond to a platform message that we sent.
+    @CalledByNative
+    private void handlePlatformMessageResponse(int responseId, String response) {
+        MessageReplyCallback callback = mPendingResponses.remove(responseId);
+        if (callback != null)
+            callback.onReply(response);
+    }
+
     @CalledByNative
     private void updateSemantics(ByteBuffer buffer, String[] strings) {
         if (mAccessibilityNodeProvider != null) {
@@ -712,12 +728,23 @@ public class FlutterView extends SurfaceView
         return true;
     }
 
+    private void dispatchPlatformMessage(String name, String message, MessageReplyCallback callback) {
+        int responseId = 0;
+        if (callback != null) {
+            responseId = mNextResponseId++;
+            mPendingResponses.put(responseId, callback);
+        }
+        nativeDispatchPlatformMessage(mNativePlatformView, name, message, responseId);
+    }
+
     /**
      * Send a message to the Flutter application.  The Flutter Dart code can register a
      * host message handler that will receive these messages.
      */
     public void sendToFlutter(String messageName, String message,
                               final MessageReplyCallback callback) {
+        // TODO(abarth): Switch to dispatchPlatformMessage once the framework
+        // side has been converted.
         mFlutterAppMessages.sendString(messageName, message,
             new ApplicationMessages.SendStringResponse() {
                 @Override

shell/platform/android/platform_view_android.cc

@@ -30,6 +30,36 @@
 #include "third_party/skia/include/core/SkSurface.h"
 
 namespace shell {
+namespace {
+
+class PlatformMessageResponseAndroid : public blink::PlatformMessageResponse {
+  FRIEND_MAKE_REF_COUNTED(PlatformMessageResponseAndroid);
+
+ public:
+  void Complete(std::vector<char> data) override {
+    ftl::RefPtr<PlatformMessageResponseAndroid> self(this);
+    blink::Threads::Platform()->PostTask(
+        [ self, data = std::move(data) ]() mutable {
+          if (!self->view_)
+            return;
+          static_cast<PlatformViewAndroid*>(self->view_.get())
+              ->HandlePlatformMessageResponse(self->response_id_,
+                                              std::move(data));
+        });
+  }
+
+  void CompleteWithError() override { Complete(std::vector<char>()); }
+
+ private:
+  PlatformMessageResponseAndroid(int response_id,
+                                 ftl::WeakPtr<PlatformView> view)
+      : response_id_(response_id), view_(view) {}
+
+  int response_id_;
+  ftl::WeakPtr<PlatformView> view_;
+};
+
+}  // namespace
 
 PlatformViewAndroid::PlatformViewAndroid()
     : PlatformView(std::make_unique<GPURasterizer>()) {}
@@ -105,6 +135,29 @@ void PlatformViewAndroid::SurfaceDestroyed(JNIEnv* env, jobject obj) {
   ReleaseSurface();
 }
 
+void PlatformViewAndroid::DispatchPlatformMessage(JNIEnv* env,
+                                                  jobject obj,
+                                                  jstring java_name,
+                                                  jstring java_message_data,
+                                                  jint response_id) {
+  std::string name = base::android::ConvertJavaStringToUTF8(env, java_name);
+  std::string data;
+  if (java_message_data)
+    data = base::android::ConvertJavaStringToUTF8(env, java_message_data);
+
+  ftl::RefPtr<blink::PlatformMessageResponse> response;
+  if (response_id) {
+    response = ftl::MakeRefCounted<PlatformMessageResponseAndroid>(
+        response_id, GetWeakPtr());
+  }
+
+  PlatformView::DispatchPlatformMessage(
+      ftl::MakeRefCounted<blink::PlatformMessage>(
+          std::move(name),
+          std::vector<char>(data.data(), data.data() + data.size()),
+          std::move(response)));
+}
+
 void PlatformViewAndroid::DispatchPointerDataPacket(JNIEnv* env,
                                                     jobject obj,
                                                     jobject buffer,
@@ -143,33 +196,47 @@ void PlatformViewAndroid::InvokePlatformMessageResponseCallback(
 void PlatformViewAndroid::HandlePlatformMessage(
     ftl::RefPtr<blink::PlatformMessage> message) {
   JNIEnv* env = base::android::AttachCurrentThread();
-  {
-    base::android::ScopedJavaLocalRef<jobject> view = flutter_view_.get(env);
-    if (view.is_null())
-      return;
+  base::android::ScopedJavaLocalRef<jobject> view = flutter_view_.get(env);
+  if (view.is_null())
+    return;
 
-    int response_id = 0;
-    if (auto response = message->response()) {
-      response_id = next_response_id_++;
-      pending_responses_[response_id] = response;
-    }
+  int response_id = 0;
+  if (auto response = message->response()) {
+    response_id = next_response_id_++;
+    pending_responses_[response_id] = response;
+  }
 
-    base::StringPiece message_name = message->name();
+  base::StringPiece message_name = message->name();
 
-    auto data = message->data();
-    base::StringPiece message_data(data.data(), data.size());
+  auto data = message->data();
+  base::StringPiece message_data(data.data(), data.size());
 
-    auto java_message_name =
-        base::android::ConvertUTF8ToJavaString(env, message_name);
-    auto java_message_data =
-        base::android::ConvertUTF8ToJavaString(env, message_data);
-    message = nullptr;
+  auto java_message_name =
+      base::android::ConvertUTF8ToJavaString(env, message_name);
+  auto java_message_data =
+      base::android::ConvertUTF8ToJavaString(env, message_data);
+  message = nullptr;
 
-    // This call can re-enter in InvokePlatformMessageResponseCallback.
-    Java_FlutterView_handlePlatformMessage(
-        env, view.obj(), java_message_name.obj(), java_message_data.obj(),
-        response_id);
-  }
+  // This call can re-enter in InvokePlatformMessageResponseCallback.
+  Java_FlutterView_handlePlatformMessage(env, view.obj(),
+                                         java_message_name.obj(),
+                                         java_message_data.obj(), response_id);
+}
+
+void PlatformViewAndroid::HandlePlatformMessageResponse(
+    int response_id,
+    std::vector<char> data) {
+  JNIEnv* env = base::android::AttachCurrentThread();
+  base::android::ScopedJavaLocalRef<jobject> view = flutter_view_.get(env);
+  if (view.is_null())
+    return;
+
+  base::StringPiece message_data(data.data(), data.size());
+  auto java_message_data =
+      base::android::ConvertUTF8ToJavaString(env, message_data);
+
+  Java_FlutterView_handlePlatformMessageResponse(env, view.obj(), response_id,
+                                                 java_message_data.obj());
 }
 
 void PlatformViewAndroid::DispatchSemanticsAction(JNIEnv* env,

shell/platform/android/platform_view_android.h

@@ -37,6 +37,12 @@ class PlatformViewAndroid : public PlatformView {
 
   void SurfaceDestroyed(JNIEnv* env, jobject obj);
 
+  void DispatchPlatformMessage(JNIEnv* env,
+                               jobject obj,
+                               jstring name,
+                               jstring message,
+                               jint response_id);
+
   void DispatchPointerDataPacket(JNIEnv* env,
                                  jobject obj,
                                  jobject buffer,
@@ -61,6 +67,8 @@ class PlatformViewAndroid : public PlatformView {
   void HandlePlatformMessage(
       ftl::RefPtr<blink::PlatformMessage> message) override;
 
+  void HandlePlatformMessageResponse(int response_id, std::vector<char> data);
+
   void RunFromSource(const std::string& main,
                      const std::string& packages,
                      const std::string& assets_directory) override;