Question

我想创建新文件和写/读应用程序设置。 isExternalStorageAvailable（）返回false并且应该为true。 Android模拟器外部存储器= 200mb。

 boolean isExternalStorageAvailable() {
        String extStorageState = Environment.getExternalStorageState();
        if (Environment.MEDIA_MOUNTED.equals(extStorageState)) {
            return true;
        }
        return false;
    }

添加了对清单文件的权限：

<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

代码：

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    if (!isExternalStorageAvailable() || isExternalStorageReadOnly()) {
        saveButton.setEnabled(false);
        System.out.println("Available: "+isExternalStorageAvailable()+", ReadOnly: "+isExternalStorageReadOnly());
    }
    else {
        myExternalFile = new File(getExternalFilesDir(filepath), filename);
    }
}

Answer 1

要获取所有外部存储路径，可以使用：

    File[] extSDCardPaths = null;
    try {
        extSDCardPaths = ContextCompat.getExternalFilesDirs(ctx, null);
    } catch (Exception e) {
        // handle
    }

    for (File f : extSDCardPaths) {
        if (Environment.isExternalStorageRemovable(f)) {
            // check if anything found
        }
    }

如果extSDCardPaths返回某些内容，则可以使用ext存储。

以上适用于＆gt; 4.4（KitKat）仅

以下hack可用作较低操作系统版本的后备：

String[] fallback = {"/storage/sdcard1/", "/mnt/ext_card/", "/mnt/extSdCard/", "/storage/extsdcard/",
            "/mnt/extsdcard/", "/storage/extSdCard/", "/mnt/external_sd", "/storage/MicroSD/",
            "/storage/external_SD/", "/storage/ext_sd/", "/storage/removable/sdcard1/", "/mnt/sdcard/external_sd/",
            "/storage/ext_sd/", "/mnt/emmc/", "/data/sdext/", "/sdcard/sd/"};

   for (String path : fallback) {
        if (new File(path).exists()) {
                // found an ext. dir
            break;
        }
   }

Answer 2

如果您的应用程序定位并在marshmallow或更高版本上运行，您必须获得读取/写入外部存储的权限，您必须在声明清单中的权限后明确请求用户的许可。

确保您的清单中有此内容：<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" /> <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

明确检查权限。如果没有提供，请求：

public void checkPermissionReadStorage(Activity activity){
         if (ContextCompat.checkSelfPermission(activity,      
Manifest.permission.READ_EXTERNAL_STORAGE) !=     
PackageManager.PERMISSION_GRANTED) {

        // Should we show an explanation?
        if (ActivityCompat.shouldShowRequestPermissionRationale(activity,
                Manifest.permission.READ_EXTERNAL_STORAGE)) {

            // Show an expanation to the user *asynchronously* -- don't block
            // this thread waiting for the user's response! After the user
            // sees the explanation, try again to request the permission.

        } else {

            // No explanation needed, we can request the permission.

            ActivityCompat.requestPermissions(activity,
                    new String[]{Manifest.permission.READ_EXTERNAL_STORAGE},
                    MY_PERMISSIONS_REQUEST_READ_STORAGE);

            // MY_PERMISSIONS_REQUEST_READ_CONTACTS is an
            // app-defined int constant. The callback method gets the
            // result of the request.
        }
    }
}

接收权限回复：

@Override
public void onRequestPermissionsResult(int requestCode,
                                       String permissions[], int[] grantResults) {
    switch (requestCode) {
        case PermissionManager.MY_PERMISSIONS_REQUEST_READ_STORAGE:
            //premission to read storage
            if (grantResults.length > 0
                    && grantResults[0] == PackageManager.PERMISSION_GRANTED) {

                // Permission granted. Call your storage related code here

            } else {

                // permission denied.
                // Handle permission failed here.
            }
            return;


        // other 'case' lines to check for other
        // permissions this app might request
    }
}

代码取自here

外部存储空间不可用

2 个答案: