Android 6.0以上，权限管理

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

// Storage Permissions
private static final int REQUEST_EXTERNAL_STORAGE = 1;
private static String[] PERMISSIONS_STORAGE = {
Manifest.permission.READ_EXTERNAL_STORAGE,
Manifest.permission.WRITE_EXTERNAL_STORAGE };
/**
* Checks if the app has permission to write to device storage
* If the app does not has permission then the user will be prompted to
* grant permissions
* @param activity
*/
public static void verifyStoragePermissions(Activity activity) {
// Check if we have write permission
int permission = ActivityCompat.checkSelfPermission(activity,
Manifest.permission.WRITE_EXTERNAL_STORAGE);

if (permission != PackageManager.PERMISSION_GRANTED) {
// We don't have permission so prompt the user
ActivityCompat.requestPermissions(activity, PERMISSIONS_STORAGE,
REQUEST_EXTERNAL_STORAGE);
}
}