在 Xamarin Android 的运行时向用户请求位置权限时应用程序崩溃答案

【问题标题】：App Crashing when requesting Location Permission from Users on Runtime in Xamarin Android在 Xamarin Android 的运行时向用户请求位置权限时应用程序崩溃
【发布时间】：2019-04-03 16:25:17
【问题描述】：

当我移动到另一个选项卡时，我只是请求位置的运行时权限（ACCESS_FINE_LOCATION），当时应用程序崩溃了。

private void RequestPermissions()
        {
            try
            {
                bool shouldProvideRationale = Android.Support.V4.App.ActivityCompat.ShouldShowRequestPermissionRationale(Activity, Manifest.Permission.AccessFineLocation);

                if (shouldProvideRationale)
                {
                    Log.Info(Tag, "Displaying permission rationale to provide additional context.");
                }
                else
                {
                    Android.Support.V4.App.ActivityCompat.RequestPermissions(Activity, new String[] { Manifest.Permission.AccessFineLocation }, 1);
                    Log.Info(Tag, "Requesting permission");
                    // StartLocationPermissionRequest();
                }
            }
}

我需要弹出窗口一直保留到我响应该权限。

【问题讨论】：

标签： android xamarin.android request location android-permissions

【解决方案1】：

您是否在清单中声明了许可？如果没有，请转到 AndroidManifest.xml 并添加：

【讨论】：

是的，我在清单中声明了此权限，但应用程序仍然崩溃

【解决方案2】：

对于完全相同的事情，我有一个可行的解决方案，如下所示：

在您的 OnCreate 方法中检查现有权限：

 if (!(CheckPermissionGranted(Manifest.Permission.AccessCoarseLocation) &&
            CheckPermissionGranted(Manifest.Permission.AccessFineLocation)))
        {
            RequestLocationPermission();
        }
        else
        {
            InitializeLocationManager();
        }
        InitPageWidgets();

Check permission Granted 是这样一种方法：

 [Export]
    public bool CheckPermissionGranted(string Permissions)
    {
        // Check if the permission is already available.
        if (ActivityCompat.CheckSelfPermission(this, Permissions) != Permission.Granted)
        {
            return false;
        }
        else
        {
            return true;
        }


    }

请求权限代码如下所示：

  private void RequestLocationPermission()
    {
        if (ActivityCompat.ShouldShowRequestPermissionRationale(this, Manifest.Permission.AccessFineLocation))
        {
            // Provide an additional rationale to the user if the permission was not granted
            // and the user would benefit from additional context for the use of the permission.
            // For example if the user has previously denied the permission.
            ActivityCompat.RequestPermissions(this, PermissionsLocation, REQUEST_LOCATION);

        }
        else
        {
            // Camera permission has not been granted yet. Request it directly.
            ActivityCompat.RequestPermissions(this, PermissionsLocation, REQUEST_LOCATION);
        }
    }

一旦您接受或拒绝此权限，此方法将被调用：

public override void OnRequestPermissionsResult(int requestCode, string[] permissions,
                     Android.Content.PM.Permission[] grantResults)
    {
        Log.Info(Tag, "onRequestPermissionResult");
        if (requestCode == RequestPermissionsRequestCode)
        {
            if (grantResults.Length <= 0)
            {
                // If user interaction was interrupted, the permission request is cancelled and you
                // receive empty arrays.
                Log.Info(Tag, "User interaction was cancelled.");
            }
            else if (grantResults[0] == PermissionChecker.PermissionGranted)
            {
                // Permission was granted.
                Service.RequestLocationUpdates();
            }
            else
            {
                // Permission denied.
                SetButtonsState(false);
                Toast.MakeText(this, "Permission Denied", ToastLength.Long).Show();
            }
        }
    }

【讨论】：