API level22下SD卡写入读取权限

SDK min 18 , compile with 25,运行在22的 AVD下,虽然在manifest文件下写了权限
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />但是实际运行中仍然被拒绝:提示

open
failed: EACCES (Permission denied)

需要在使用权限之前询问:

// 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
);
}
}

在使用前调用verifyStoragePermission方法,暂时解决了. (在stackoverflow看到的解决方法之一,使用有效)

2017 .1.11
实际上就这三行代码

int code = checkSelfPermission("android.permission.READ_CONTACTS");
if(code!= PackageManager.PERMISSION_GRANTED)
requestPermissions(new String[]{"android.permission.READ_CONTACTS"},1);