[Xamarin][原创]Android SD卡读写 动态权限添加

先 要在AndroidManifest.xml文件中添加权限

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
然后Activity中设置两个私有静态变量

private static final int REQUEST_EXTERNAL_STORAGE = 1;
private static String[] PERMISSIONS_STORAGE = {
        "android.permission.READ_EXTERNAL_STORAGE",
        "android.permission.WRITE_EXTERNAL_STORAGE" };
然后在Activity中的onCreate引用方法
 protected override void OnCreate(Bundle savedInstanceState)
        {
            base.OnCreate(savedInstanceState);
            Xamarin.Essentials.Platform.Init(this, savedInstanceState);
            // Set our view from the "main" layout resource
            SetContentView(Resource.Layout.activity_main);
            verifyStoragePermissions(this);
        }

 public void verifyStoragePermissions(Activity activity)
        {
            try
            {
                //检测是否有写的权限
                var permission = ActivityCompat.CheckSelfPermission(activity,"android.permission.WRITE_EXTERNAL_STORAGE");
                if (permission != Android.Content.PM.Permission.Granted)
                {
                    // 没有写的权限，去申请写的权限，会弹出对话框
                    ActivityCompat.RequestPermissions(activity, PERMISSIONS_STORAGE, REQUEST_EXTERNAL_STORAGE);
                }
            }
            catch (Exception ex)
            {
                Toast.MakeText(activity, ex.Message, ToastLength.Short).Show();
            }
        }