Allow passing extra creation parameters for embedded Android views. (flutter/engine#6081)

This allows plugins to pass extra parameters from the Dart side to the
platform view constructor.

engine/src/flutter/shell/platform/android/io/flutter/plugin/platform/PlatformViewFactory.java

@@ -5,13 +5,34 @@
 package io.flutter.plugin.platform;
 
 import android.content.Context;
+import io.flutter.plugin.common.MessageCodec;
+
+public abstract class PlatformViewFactory {
+    private final MessageCodec<Object> mCreateArgsCodec;
+
+    /**
+     *
+     * @param createArgsCodec the codec used to decode the args parameter of {@link #create}.
+     */
+    public PlatformViewFactory(MessageCodec<Object> createArgsCodec) {
+        mCreateArgsCodec = createArgsCodec;
+    }
 
-public interface PlatformViewFactory {
     /**
      * Creates a new Android view to be embedded in the Flutter hierarchy.
      *
      * @param context the context to be used when creating the view, this is different than FlutterView's context.
      * @param viewId unique identifier for the created instance, this value is known on the Dart side.
+     * @param args arguments sent from the Flutter app. The bytes for this value are decoded using the createArgsCodec
+     *             argument passed to the constructor. This is null if createArgsCodec was null, or no arguments were
+     *             sent from the Flutter app.
      */
-    PlatformView create(Context context, int viewId);
+    public abstract PlatformView create(Context context, int viewId, Object args);
+
+    /**
+     * Returns the codec to be used for decoding the args parameter of {@link #create}.
+     */
+    public final MessageCodec<Object> getCreateArgsCodec() {
+        return mCreateArgsCodec;
+    }
 }

engine/src/flutter/shell/platform/android/io/flutter/plugin/platform/PlatformViewsController.java

@@ -15,6 +15,7 @@ import io.flutter.plugin.common.StandardMethodCodec;
 import io.flutter.view.FlutterView;
 import io.flutter.view.TextureRegistry;
 
+import java.nio.ByteBuffer;
 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
@@ -140,6 +141,11 @@ public class PlatformViewsController implements MethodChannel.MethodCallHandler
             return;
         }
 
+        Object createParams = null;
+        if (args.containsKey("params")) {
+            createParams = viewFactory.getCreateArgsCodec().decodeMessage(ByteBuffer.wrap((byte[]) args.get("params")));
+        }
+
         TextureRegistry.SurfaceTextureEntry textureEntry = mFlutterView.createSurfaceTexture();
         VirtualDisplayController vdController = VirtualDisplayController.create(
                 mFlutterView.getContext(),
@@ -147,7 +153,8 @@ public class PlatformViewsController implements MethodChannel.MethodCallHandler
                 textureEntry.surfaceTexture(),
                 toPhysicalPixels(logicalWidth),
                 toPhysicalPixels(logicalHeight),
-                id
+                id,
+                createParams
         );
 
         if (vdController == null) {

engine/src/flutter/shell/platform/android/io/flutter/plugin/platform/SingleViewPresentation.java

@@ -58,9 +58,13 @@ class SingleViewPresentation extends Presentation {
     private final PlatformViewFactory mViewFactory;
 
     // This is the view id assigned by the Flutter framework to the embedded view, we keep it here
-    // so when we create the platform we can tell it its view id.
+    // so when we create the platform view we can tell it its view id.
     private int mViewId;
 
+    // This is the creation parameters for the platform view, we keep it here
+    // so when we create the platform view we can tell it its view id.
+    private Object mCreateParams;
+
     // The root view for the presentation, it has 2 childs: mContainer which contains the embedded view, and
     // mFakeWindowRootView which contains views that were added directly to the presentation's window manager.
     private FrameLayout mRootView;
@@ -74,10 +78,16 @@ class SingleViewPresentation extends Presentation {
      * Creates a presentation that will use the view factory to create a new
      * platform view in the presentation's onCreate, and attach it.
      */
-    public SingleViewPresentation(Context outerContext, Display display, PlatformViewFactory viewFactory, int viewId) {
+    public SingleViewPresentation(
+            Context outerContext,
+            Display display,
+            PlatformViewFactory viewFactory,
+            int viewId,
+            Object createParams) {
         super(outerContext, display);
         mViewFactory = viewFactory;
         mViewId = viewId;
+        mCreateParams = createParams;
         mState = new PresentationState();
         getWindow().setFlags(
                 WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE,
@@ -117,7 +127,7 @@ class SingleViewPresentation extends Presentation {
         PresentationContext context = new PresentationContext(getContext(), mState.mWindowManagerHandler);
 
         if (mState.mView == null) {
-            mState.mView = mViewFactory.create(context, mViewId);
+            mState.mView = mViewFactory.create(context, mViewId, mCreateParams);
         }
 
         mContainer.addView(mState.mView.getView());

engine/src/flutter/shell/platform/android/io/flutter/plugin/platform/VirtualDisplayController.java

@@ -23,7 +23,8 @@ class VirtualDisplayController {
             SurfaceTexture surfaceTexture,
             int width,
             int height,
-            int viewId
+            int viewId,
+            Object createParams
     ) {
         surfaceTexture.setDefaultBufferSize(width, height);
         Surface surface = new Surface(surfaceTexture);
@@ -43,7 +44,8 @@ class VirtualDisplayController {
             return null;
         }
 
-        return new VirtualDisplayController(context, virtualDisplay, viewFactory, surface, surfaceTexture, viewId);
+        return new VirtualDisplayController(
+                context, virtualDisplay, viewFactory, surface, surfaceTexture, viewId, createParams);
     }
 
     private final Context mContext;
@@ -60,14 +62,16 @@ class VirtualDisplayController {
             PlatformViewFactory viewFactory,
             Surface surface,
             SurfaceTexture surfaceTexture,
-            int viewId
+            int viewId,
+            Object createParams
     ) {
         mSurfaceTexture = surfaceTexture;
         mSurface = surface;
         mContext = context;
         mVirtualDisplay = virtualDisplay;
         mDensityDpi = context.getResources().getDisplayMetrics().densityDpi;
-        mPresentation = new SingleViewPresentation(context, mVirtualDisplay.getDisplay(), viewFactory, viewId);
+        mPresentation = new SingleViewPresentation(
+                context, mVirtualDisplay.getDisplay(), viewFactory, viewId, createParams);
         mPresentation.show();
     }