How do I share an image on iOS and Android using Flutter?

Question

I would like to share an image using the standard share dialogs in iOS and Android. The code below is mostly from https://pub.dartlang.org/packages/share which I'm using as a starting point (only Dart and Objective-C below). It currently shares only text.

Instead of Image below which I'm not sure is the best approach, how would I convert the image to a byte stream in Dart and handle in iOS and Android.

Dart

static const _kShareChannel = const MethodChannel('example.test.com/share'); Future<Null> shareImage(Image image) {   assert(image != null);   return _kShareChannel.invokeMethod('shareImage', image); } 

Objective-C

static NSString *const PLATFORM_CHANNEL = @"example.test.com/share";  - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {     [GeneratedPluginRegistrant registerWithRegistry:self];      FlutterViewController* controller = (FlutterViewController*)self.window.rootViewController;      FlutterMethodChannel *shareChannel = [FlutterMethodChannel methodChannelWithName:PLATFORM_CHANNEL                             binaryMessenger:controller];      [shareChannel setMethodCallHandler:^(FlutterMethodCall *call, FlutterResult result) {         if ([@"shareImage" isEqualToString:call.method]) {             [self share:call.arguments withController:[UIApplication sharedApplication].keyWindow.rootViewController];             result(nil);         } else {             result([FlutterError errorWithCode:@"UNKNOWN_METHOD"                                        message:@"Unknown share method called"                                        details:nil]);         }     }];     return [super application:application didFinishLaunchingWithOptions:launchOptions]; }  - (void)share:(id)sharedItems withController:(UIViewController *)controller {     UIActivityViewController *activityViewController = [[UIActivityViewController alloc] initWithActivityItems:@[ sharedItems ]                                   applicationActivities:nil];     [controller presentViewController:activityViewController animated:YES completion:nil]; } 

Answer 1

The below will allow you to send a file (specifically an image in this example) using UIActivityViewController on iOS and as a share intent on Android.

FileProvider overview (Android)

Update pubspec.yaml to reference your image if local (image.jpg in this example) and to use the path_provider plugin in order to access the file system. https://pub.dartlang.org/packages/path_provider

main.dart

import 'dart:io'; import 'dart:typed_data';  import 'package:flutter/material.dart'; import 'package:flutter/services.dart'; import 'package:path_provider/path_provider.dart';  void main() => runApp(new MyApp());  class MyApp extends StatelessWidget {   @override   Widget build(BuildContext context) {     return new MaterialApp(       title: 'Share Demo',       theme: new ThemeData(         primarySwatch: Colors.blue,       ),       home: new MyHomePage(title: 'Share Demo Home Page'),     );   } }  class MyHomePage extends StatefulWidget {   MyHomePage({Key key, this.title}) : super(key: key);    final String title;    @override   _MyHomePageState createState() => new _MyHomePageState(); }  class _MyHomePageState extends State<MyHomePage> {    @override   Widget build(BuildContext context) {      return new Scaffold(       appBar: new AppBar(         title: new Text(widget.title),       ),       body: new Center(         child: new Column(           mainAxisAlignment: MainAxisAlignment.center,           children: <Widget>[           ],         ),       ),       floatingActionButton: new FloatingActionButton(         onPressed: _shareImage,         tooltip: 'Share',         child: new Icon(Icons.share),       ),     );   }    _shareImage() async {     try {       final ByteData bytes = await rootBundle.load('assets/image.jpg');       final Uint8List list = bytes.buffer.asUint8List();        final tempDir = await getTemporaryDirectory();       final file = await new File('${tempDir.path}/image.jpg').create();       file.writeAsBytesSync(list);        final channel = const MethodChannel('channel:me.albie.share/share');       channel.invokeMethod('shareFile', 'image.jpg');      } catch (e) {       print('Share error: $e');     }   } } 

AppDelegate.m

#include "AppDelegate.h" #include "GeneratedPluginRegistrant.h"  @implementation AppDelegate  static NSString *const SHARE_CHANNEL = @"channel:me.albie.share/share";  - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {     [GeneratedPluginRegistrant registerWithRegistry:self];     FlutterViewController* controller = (FlutterViewController*)self.window.rootViewController;      FlutterMethodChannel *shareChannel =     [FlutterMethodChannel methodChannelWithName:SHARE_CHANNEL                                 binaryMessenger:controller];      [shareChannel setMethodCallHandler:^(FlutterMethodCall *call, FlutterResult result) {         if ([@"shareFile" isEqualToString:call.method]) {             [self shareFile:call.arguments              withController:[UIApplication sharedApplication].keyWindow.rootViewController];         }     }];      return [super application:application didFinishLaunchingWithOptions:launchOptions]; }  - (void)shareFile:(id)sharedItems withController:(UIViewController *)controller {     NSMutableString *filePath = [NSMutableString stringWithString:sharedItems];     NSString *docsPath = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) objectAtIndex:0];     NSString *imagePath = [docsPath stringByAppendingPathComponent:filePath];     NSURL *imageUrl = [NSURL fileURLWithPath:imagePath];     NSData *imageData = [NSData dataWithContentsOfURL:imageUrl];     UIImage *shareImage = [UIImage imageWithData:imageData];      UIActivityViewController *activityViewController =     [[UIActivityViewController alloc] initWithActivityItems:@[ shareImage ]                                       applicationActivities:nil];     [controller presentViewController:activityViewController animated:YES completion:nil]; }  @end 

MainActivity.java

package com.example.share;  import android.content.Intent; import android.net.Uri; import android.os.Bundle;  import java.io.File;  import io.flutter.app.FlutterActivity; import io.flutter.plugin.common.MethodCall; import io.flutter.plugin.common.MethodChannel; import io.flutter.plugins.GeneratedPluginRegistrant;  import android.support.v4.content.FileProvider;  public class MainActivity extends FlutterActivity {      private static final String SHARE_CHANNEL = "channel:me.albie.share/share";      @Override     protected void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         GeneratedPluginRegistrant.registerWith(this);          new MethodChannel(this.getFlutterView(), SHARE_CHANNEL).setMethodCallHandler(new MethodChannel.MethodCallHandler() {             public final void onMethodCall(MethodCall methodCall, MethodChannel.Result result) {                 if (methodCall.method.equals("shareFile")) {                     shareFile((String) methodCall.arguments);                 }             }         });     }      private void shareFile(String path) {         File imageFile = new File(this.getApplicationContext().getCacheDir(), path);         Uri contentUri = FileProvider.getUriForFile(this, "me.albie.share", imageFile);         Intent shareIntent = new Intent(Intent.ACTION_SEND);         shareIntent.setType("image/jpg");         shareIntent.putExtra(Intent.EXTRA_STREAM, contentUri);         this.startActivity(Intent.createChooser(shareIntent, "Share image using"));     } } 

AndroidManifest.xml

<provider     android:name="android.support.v4.content.FileProvider"     android:authorities="me.albie.share"     android:exported="false"     android:grantUriPermissions="true">     <meta-data         android:name="android.support.FILE_PROVIDER_PATHS"         android:resource="@xml/file_paths" /> </provider> 

xml/file_paths.xml

<?xml version="1.0" encoding="utf-8"?> <paths>     <cache-path name="images" path="/"/> </paths> 

build.gradle (app)

dependencies {     ...     implementation 'com.android.support:support-v4:27.1.1' }