方向更改后重复的权限请求

Question

由于Android SDK 23允许用户拒绝应用访问某些功能,我想更新我的某个应用以请求权限,如下所述:https://developer.android.com/preview/features/runtime- permissions.html.

在其中一个活动中,我嵌入了一个SupportMapFragment.要使其工作,您需要拥有WRITE_EXTERNAL_STORAGE权限,因此我在启动活动时请求它,这会导致创建权限请求对话框.

现在的问题是,当对话框仍然打开并且我旋转设备时,活动将重新启动并打开一个新的权限请求对话框,而旧的仍然存在.结果是其中两个对话框彼此叠加,其中只有一个是有用的.

有没有办法摆脱首先启动的对话框？

Answer 1

正如CommonsWare在他的评论中所说,最好的解决方案是将一个布尔值放入savedInstanceState-Bundle中,以了解该对话框是否仍处于打开状态.

例:

// true if dialog already open
private boolean alreadyAskedForStoragePermission = false;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    if(savedInstanceState != null) {
        alreadyAskedForStoragePermission = savedInstanceState.getBoolean(STORAGE_PERMISSION_DIALOG_OPEN_KEY, false);
    }
}

@Override
protected void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);

    outState.putBoolean(KEY, alreadyAskedForStoragePermission);
}

private void checkStoragePermission(){
    if(alreadyAskedForStoragePermission){
        // don't check again because the dialog is still open
        return;
    }

    if(ActivityCompat.checkSelfPermission(this, STORAGE_PERMISSIONS[0]) != PackageManager.PERMISSION_GRANTED){
        // the dialog will be opened so we have to keep that in memory
        alreadyAskedForStoragePermission = true;
        ActivityCompat.requestPermissions(this, STORAGE_PERMISSIONS, STORAGE_PERMISSION_REQUEST_CODE);
    } else {
        onStoragePermissionGranted();
    }
}

@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
    switch (requestCode){
        case STORAGE_PERMISSION_REQUEST_CODE:
            // the request returned a result so the dialog is closed
            alreadyAskedForStoragePermission = false;

            if(grantResults[0] == PackageManager.PERMISSION_GRANTED){
                onStoragePermissionGranted();
            }

            break;
    }
}

Answer 2

正如@ user1991776所提到的,实际上有一个未记录的额外内容,其中包含当前是否打开了一个权限对话框,在Activity中:

private static final String HAS_CURENT_PERMISSIONS_REQUEST_KEY =
        "android:hasCurrentPermissionsRequest";

但是有更好的方法.当您第二次请求权限对话框(由于轮换)时,Activity通过调用onRequestPermissionResult() 空数组自动取消旧对话框:

public final void requestPermissions(@NonNull String[] permissions, int requestCode) {
    if (mHasCurrentPermissionsRequest) {
        Log.w(TAG, "Can reqeust only one set of permissions at a time");
        // Dispatch the callback with empty arrays which means a cancellation.
        onRequestPermissionsResult(requestCode, new String[0], new int[0]);
        return;
    }
    Intent intent = getPackageManager().buildRequestPermissionsIntent(permissions);
    startActivityForResult(REQUEST_PERMISSIONS_WHO_PREFIX, intent, requestCode, null);
    mHasCurrentPermissionsRequest = true;
}

或者当然没有记录这种行为,因为这是Android,谁想记录复杂的行为？

无论如何,您可以随时请求权限onCreate(),然后忽略对onRequestPermissionsResult()零长度permissions数组的调用.