ZXing.Net.Mobile的Xamarin.Android摄像头权限仅在应用重启后有效

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

using Android;
using Android.Content.PM;
using Android.Support.V4.App;
using Android.Support.V4.Content;

...

private const int RequestCameraPermissionId = 1001;

private void RequestCameraPermission()
{
    if (ContextCompat.CheckSelfPermission(this, Manifest.Permission.Camera) != (int)Permission.Granted)
    {
        if (ActivityCompat.ShouldShowRequestPermissionRationale(this, Manifest.Permission.Camera))
        {
            // TODO: 解释为什么需要摄像头权限
        }

        ActivityCompat.RequestPermissions(this, new string[] { Manifest.Permission.Camera }, RequestCameraPermissionId);
    }
}

public override void OnRequestPermissionsResult(int requestCode, string[] permissions, Permission[] grantResults)
{
    if (requestCode == RequestCameraPermissionId)
    {
        if (grantResults.Length > 0 && grantResults[0] == Permission.Granted)
        {
            // 摄像头权限已授权
        }
        else
        {
            // 摄像头权限被拒绝
        }
    }
}