Add method for external storage

Android supports accessing the "external" storage medium. Support
finding this path in flutter with a method call in path_provider

Author: natelust

packages/path-provider/CHANGELOG.md

@@ -1,3 +1,7 @@
+## [0.2.1] - 2017-05-16
+
+* Add function to determine external storage directory.
+
 ## [0.2.0] - 2017-05-10
 
 * Upgrade to new plugin registration. (https://groups.google.com/forum/#!topic/flutter-dev/zba1Ynf2OKM)

packages/path-provider/android/src/main/java/io/flutter/plugins/path_provider/PathProviderPlugin.java

@@ -5,6 +5,7 @@
 package io.flutter.plugins.path_provider;
 
 import android.app.Activity;
+import android.os.Environment;
 import io.flutter.plugin.common.MethodCall;
 import io.flutter.plugin.common.MethodChannel;
 import io.flutter.plugin.common.MethodChannel.MethodCallHandler;
@@ -35,6 +36,9 @@ public void onMethodCall(MethodCall call, Result result) {
       case "getApplicationDocumentsDirectory":
         result.success(getPathProviderApplicationDocumentsDirectory());
         break;
+      case "getStorageDirectory":
+        result.success(getPathProviderStorageDirectory());
+        break;
       default:
         result.notImplemented();
     }
@@ -47,4 +51,8 @@ private String getPathProviderTemporaryDirectory() {
   private String getPathProviderApplicationDocumentsDirectory() {
     return PathUtils.getDataDirectory(activity);
   }
+
+  private String getPathProviderStorageDirectory() {
+    return Environment.getExternalStorageDirectory().getAbsolutePath();
+  }
 }

packages/path-provider/example/lib/main.dart

@@ -36,6 +36,7 @@ class MyHomePage extends StatefulWidget {
 class _MyHomePageState extends State<MyHomePage> {
   Future<Directory> _tempDirectory;
   Future<Directory> _appDocumentsDirectory;
+  Future<Directory> _externalDocumentsDirectory;
 
   void _requestTempDirectory() {
     setState(() {
@@ -65,6 +66,12 @@ class _MyHomePageState extends State<MyHomePage> {
     });
   }
 
+  void _requestExternalStorageDirectory() {
+    setState(() {
+      _externalDocumentsDirectory = getExternalStorageDirectory();
+    });
+  }
+
   @override
   Widget build(BuildContext context) {
     return new Scaffold(
@@ -105,6 +112,25 @@ class _MyHomePageState extends State<MyHomePage> {
               child: new FutureBuilder<Directory>(
                   future: _appDocumentsDirectory, builder: _buildDirectory),
             ),
+            new Column(
+              children : <Widget>[
+                new Padding(
+                  padding: const EdgeInsets.all(16.0),
+                  child: new RaisedButton(
+                    child: new Text('${Platform.isIOS ?
+                                    "External directories are unavailable " +
+                                    "on iOS":
+                                    "Get External Storage Directory" }'),
+                    onPressed: Platform.isIOS ? null :
+                      _requestExternalStorageDirectory,
+                  ),
+                ),
+              ]
+            ),
+            new Expanded(
+              child: new FutureBuilder<Directory>(
+               future: _externalDocumentsDirectory, builder: _buildDirectory),
+            ),
           ],
         ),
       ),

packages/path-provider/lib/path_provider.dart

@@ -40,3 +40,20 @@ const _channel = const MethodChannel('plugins.flutter.io/path_provider');
       return null;
     return new Directory(path);
   }
+
+  /// Path to a directory where the application may access top level storage.
+  /// The current operating system should be determined before issuing this
+  /// function call, as this functionality is only available on Android.
+  ///
+  /// On iOS, this function throws an UnsupportedError as it is not possible
+  /// to access outside the app's sandbox.
+  ///
+  /// On Android this returns getExternalStorageDirectory.
+  Future<Directory> getExternalStorageDirectory() async {
+    if (Platform.isIOS)
+      throw new UnsupportedError("Functionality not available on iOS");
+    final String path = await _channel.invokeMethod('getStorageDirectory');
+    if (path == null)
+      return null;
+    return new Directory(path);
+  }

packages/path-provider/pubspec.yaml

@@ -1,6 +1,6 @@
 name: path_provider
 
-version: 0.2.0
+version: 0.2.1
 description: A Flutter plugin for getting commonly used locations on the filesystem.
 author: Flutter Team <[email protected]>
 homepage: https://github.com/flutter/plugins/tree/master/packages/path_provider