使用新的 registerForActivityResult 请求在 DialogFragment 中写入的权限

我尝试提醒用户在退出活动时将数据保存在文件中。因此，我显示一个对话框，询问他们是否要存储数据。这里我需要检查是否授予了权限。如果没有，请请求它，一旦被授予，就写入文件。

我无法在 DialogFragment 中捕获 onRequestPermissionResult 回调，因此我开始使用新的 registerForActivityResult。问题是，当尚未授予权限时，弹出窗口会显示请求权限，但当授予权限时，不会调用回调。如果我再次按下关闭按钮，则会检查权限，并且回调现在会收到“已授予”，而不显示弹出窗口。

这是我在 DialogFragment 中的代码：

class SaveCalibrationDialogFragment(val data: String) : DialogFragment() {
    private val activityResultLauncher = registerForActivityResult(
        ActivityResultContracts.RequestPermission()) { isGranted ->
        println("Received CallBack")
        if (isGranted) {
            println("Permission granted!")
        } else {
            println("Permission needed!")
        }
    }

    override fun onCreateDialog(savedInstanceState: Bundle?): Dialog {
        val builder = AlertDialog.Builder(this.requireContext())
        val dialog = builder.setTitle("Notice")
            .setMessage("Data is not saved. Do you want to save before exiting?")
            .setNegativeButton("No") { dialog, _ ->
            }.setPositiveButton("Yes") { _, _ ->
                activityResultLauncher?.launch(WRITE_EXTERNAL_STORAGE)
            }
            .create()
        return dialog
    }

}

活动：

cancel.setOnClickListener {
        if (viewModel.isDataSave && viewModel.isLastPage) {
            setResult(Activity.RESULT_OK, intent)
            finish()
        } else if (!viewModel.isDataSave && viewModel.isLastPage){
            SaveCalibrationDialogFragment(viewModel.dataToSave!!).show(this.supportFragmentManager, "costumeSaveDialog")
        } else {
            setResult(Activity.RESULT_CANCELED, intent)
            finish()
        }

    }

“问题是......当授予权限时，不会调用回调”

也许这就是为什么在调用“launch(...)”之前检查是否已授予权限是常见的原因。

Example

将回调存储在单独的变量中（myCallback)，然后更改为：

activityResultLauncher?.launch(WRITE_EXTERNAL_STORAGE)

变成这样的东西：

Activity activity = this;
String permission = Manifest.permission.WRITE_EXTERNAL_STORAGE;

if (ContextCompat.checkSelfPermission(activity, permission)
        == PackageManager.PERMISSION_GRANTED
) {
    // Already granted permission.
    myCallback.onActivityResult(true);
} else if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M
        && activity.shouldShowRequestPermissionRationale(permission)
) {
    // Permission denied permanently (by "Never ask again" checkbox).
    myCallback.onActivityResult(false);
} else {
    // At last, ask for permission.
    activityResultLauncher?.launch(WRITE_EXTERNAL_STORAGE);
}