android - Flutter:getApplicationDocumentsDirectory() 返回 null

Question

getApplicationDocumentsDirectory() 方法返回 null。我想不通为什么....

getApplicationDocumentsDirectory().then((directory) {
  print(_directory);
  _directory = directory;
});

null 打印到控制台...

我需要注册一些东西或请求许可吗？

Answer 1

您需要获得 WRITE_EXTERNAL_STORAGE 和 READ_EXTERNAL_STORAGE 权限。

在您的 list 中添加如下:

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.xxx.yyy">
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
...
</manifest>

并且还需要运行时请求权限，通过使用 simple_permissions 包。引用以下代码:

    import 'package:simple_permissions/simple_permissions.dart';

    PermissionStatus permissionResult = await SimplePermissions.requestPermission(Permission. WriteExternalStorage);
    if (permissionResult == PermissionStatus.authorized){
      // code of read or write file in external storage (SD card)
      getApplicationDocumentsDirectory().then((directory) {
        print(_directory);
        _directory = directory;
     });
    }

Refer to this tutorial for learning more about using runtime permission in flutter.