Maps snapshot

packages/google_maps_flutter/android/src/main/java/io/flutter/plugins/googlemaps/GoogleMapController.java

@@ -17,6 +17,7 @@
 import android.app.Application;
 import android.content.Context;
 import android.content.pm.PackageManager;
+import android.graphics.Bitmap;
 import android.os.Bundle;
 import android.util.Log;
 import android.view.View;
@@ -37,6 +38,7 @@
 import io.flutter.plugin.common.MethodChannel;
 import io.flutter.plugin.common.PluginRegistry;
 import io.flutter.plugin.platform.PlatformView;
+import java.io.ByteArrayOutputStream;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashMap;
@@ -60,6 +62,7 @@ final class GoogleMapController
         OnMapReadyCallback,
         GoogleMap.OnMapClickListener,
         GoogleMap.OnMapLongClickListener,
+        GoogleMap.SnapshotReadyCallback,
         PlatformView {
 
   private static final String TAG = "GoogleMapController";
@@ -220,6 +223,11 @@ public void onMethodCall(MethodCall call, MethodChannel.Result result) {
           }
           break;
         }
+      case "map#snapshot":
+        {
+          googleMap.snapshot(this);
+          break;
+        }
       case "camera#move":
         {
           final CameraUpdate cameraUpdate =
@@ -403,6 +411,15 @@ public void onCircleClick(Circle circle) {
     circlesController.onCircleTap(circle.getId());
   }
 
+  @Override
+  public void onSnapshotReady(Bitmap bitmap) {
+    ByteArrayOutputStream stream = new ByteArrayOutputStream();
+    bitmap.compress(Bitmap.CompressFormat.PNG, 100, stream);
+    byte[] byteArray = stream.toByteArray();
+    bitmap.recycle();
+    methodChannel.invokeMethod("map#onSnapshot", byteArray);
+  }
+
   @Override
   public void dispose() {
     if (disposed) {

packages/google_maps_flutter/example/lib/map_ui.dart

@@ -2,6 +2,9 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'dart:typed_data';
+import 'dart:ui' as ui;
+
 import 'package:flutter/material.dart';
 import 'package:google_maps_flutter/google_maps_flutter.dart';
 import 'package:flutter/services.dart' show rootBundle;
@@ -186,6 +189,14 @@ class MapUiBodyState extends State<MapUiBody> {
     );
   }
 
+  Widget _snapshotter() {
+    return FlatButton(
+        child: const Text('make snapshot'),
+        onPressed: () {
+          _controller.snapshot();
+        });
+  }
+
   Future<String> _getFileData(String path) async {
     return await rootBundle.loadString(path);
   }
@@ -232,6 +243,7 @@ class MapUiBodyState extends State<MapUiBody> {
       myLocationEnabled: _myLocationEnabled,
       myLocationButtonEnabled: _myLocationButtonEnabled,
       onCameraMove: _updateCameraPosition,
+      onSnapshot: _snapshot,
     );
 
     final List<Widget> columnChildren = <Widget>[
@@ -269,6 +281,7 @@ class MapUiBodyState extends State<MapUiBody> {
               _zoomToggler(),
               _myLocationToggler(),
               _myLocationButtonToggler(),
+              _snapshotter(),
               _nightModeToggler(),
             ],
           ),
@@ -289,9 +302,35 @@ class MapUiBodyState extends State<MapUiBody> {
   }
 
   void onMapCreated(GoogleMapController controller) {
+    _controller = controller;
     setState(() {
       _controller = controller;
       _isMapCreated = true;
     });
   }
+
+  void _snapshot(Uint8List argument) async {
+    final ui.Codec codec = await ui.instantiateImageCodec(argument);
+    final ui.FrameInfo frame = await codec.getNextFrame();
+    final ui.Image img = frame.image;
+    print('${argument.length} bytes, ${img.width} x ${img.height} px');
+    await showDialog<void>(
+      context: context,
+      builder: (BuildContext context) {
+        return AlertDialog(
+            actions: <Widget>[
+              FlatButton(
+                child: const Text('OK'),
+                onPressed: () => Navigator.of(context).pop(),
+              )
+            ],
+            content: Padding(
+                padding: const EdgeInsets.symmetric(vertical: 66),
+                child: Row(
+                  mainAxisAlignment: MainAxisAlignment.spaceAround,
+                  children: <Widget>[Image.memory(argument)],
+                )));
+      },
+    );
+  }
 }

packages/google_maps_flutter/ios/Classes/GoogleMapController.m

@@ -136,6 +136,14 @@ - (void)onMethodCall:(FlutterMethodCall*)call result:(FlutterResult)result {
   } else if ([call.method isEqualToString:@"map#update"]) {
     InterpretMapOptions(call.arguments[@"options"], self);
     result(PositionToJson([self cameraPosition]));
+  } else if ([call.method isEqualToString:@"map#snapshot"]) {
+    UIGraphicsBeginImageContext(_mapView.frame.size);
+    [_mapView.layer renderInContext:UIGraphicsGetCurrentContext()];
+    UIImage* screenShotImage = UIGraphicsGetImageFromCurrentImageContext();
+    NSData* imageData = UIImagePNGRepresentation(screenShotImage);
+    [_channel invokeMethod:@"map#onSnapshot" arguments:imageData];
+    UIGraphicsEndImageContext();
+    result(nil);
   } else if ([call.method isEqualToString:@"map#getVisibleRegion"]) {
     if (_mapView != nil) {
       GMSVisibleRegion visibleRegion = _mapView.projection.visibleRegion;

packages/google_maps_flutter/lib/src/controller.dart

@@ -76,6 +76,9 @@ class GoogleMapController {
         _googleMapState
             .onLongPress(LatLng._fromJson(call.arguments['position']));
         break;
+      case 'map#onSnapshot':
+        _googleMapState.onSnaphot(call.arguments);
+        break;
       default:
         throw MissingPluginException();
     }
@@ -204,4 +207,9 @@ class GoogleMapController {
 
     return LatLngBounds(northeast: northeast, southwest: southwest);
   }
+
+  /// Ask for a snapshot to be returned via onSnapshot event
+  Future<void> snapshot() async {
+    await channel.invokeMethod<void>('map#snapshot');
+  }
 }

packages/google_maps_flutter/lib/src/google_map.dart

@@ -39,6 +39,7 @@ class GoogleMap extends StatefulWidget {
     this.onCameraIdle,
     this.onTap,
     this.onLongPress,
+    this.onSnapshot,
   })  : assert(initialCameraPosition != null),
         super(key: key);
 
@@ -112,6 +113,9 @@ class GoogleMap extends StatefulWidget {
   /// Called every time a [GoogleMap] is long pressed.
   final ArgumentCallback<LatLng> onLongPress;
 
+  /// Called when a snapshot has completed
+  final ArgumentCallback<Uint8List> onSnapshot;
+
   /// True if a "My Location" layer should be shown on the map.
   ///
   /// This layer includes a location indicator at the current device location,
@@ -328,6 +332,13 @@ class _GoogleMapState extends State<GoogleMap> {
       widget.onLongPress(position);
     }
   }
+
+  void onSnaphot(Uint8List imgData) {
+    assert(imgData != null);
+    if (widget.onSnapshot != null) {
+      widget.onSnapshot(imgData);
+    }
+  }
 }
 
 /// Configuration options for the GoogleMaps user interface.