问检测闪光灯是否已打开

EN

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="20dp"
        android:text="Please see following switch"/>
<Switch
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
        android:id="@+id/switch1"/>
<Button
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:id="@+id/button1" 
        android:text="start"/>

    <Button
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:id="@+id/button2" 
        android:text="Stop"/>

    <EditText
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="123@456"/>
</LinearLayout>

   [Activity(Label = "@string/app_name", Theme = "@style/AppTheme", MainLauncher = true)]
    public class MainActivity : AppCompatActivity
    {
        public static MainActivity Instance;
        public static Switch switch1;
        protected override void OnCreate(Bundle savedInstanceState)
        {
            base.OnCreate(savedInstanceState);
            Xamarin.Essentials.Platform.Init(this, savedInstanceState);
            Instance = this;
            // Set our view from the "main" layout resource
            SetContentView(Resource.Layout.activity_main);
            Button button1 = FindViewById<Button>(Resource.Id.button1);
            Button button2 = FindViewById<Button>(Resource.Id.button2);
            switch1 = FindViewById<Switch>(Resource.Id.switch1);
          
            button2.Click += Button2_Click;
            button1.Click += Button1_Click;
        }
        Intent intent;
        private void Button2_Click(object sender, System.EventArgs e)
        {
            // throw new System.NotImplementedException();
            Android.App.Application.Context.StopService(intent);
        }

        private void Button1_Click(object sender, System.EventArgs e)
        {
             intent = new Intent(Android.App.Application.Context, typeof(MyForegroundService));


            if (Android.OS.Build.VERSION.SdkInt >= Android.OS.BuildVersionCodes.O)
            {
                StartForegroundService(intent);
               // Android.App.Application.Context.StartForegroundService(intent);
            }
        }

        public override void OnRequestPermissionsResult(int requestCode, string[] permissions, [GeneratedEnum] Android.Content.PM.Permission[] grantResults)
        {
            Xamarin.Essentials.Platform.OnRequestPermissionsResult(requestCode, permissions, grantResults);

            base.OnRequestPermissionsResult(requestCode, permissions, grantResults);
        }
    }
}

using Android.Hardware.Camera2;
using Android.OS;
using Android.Runtime;
using Android.Views;
using Android.Widget;
using Xamarin.Essentials;

namespace ForegroundServiceDemo
{
    [Service]
    class MyForegroundService : Service
    {
        public const int SERVICE_RUNNING_NOTIFICATION_ID = 10000;

        [return: GeneratedEnum]
        public override StartCommandResult OnStartCommand(Intent intent, [GeneratedEnum] StartCommandFlags flags, int startId)
        {
            CreateNotificationChannel();
            string messageBody = "service starting";


            Clipboard.ClipboardContentChanged += Clipboard_ClipboardContentChanged;

             // / Create an Intent for the activity you want to start
             Intent resultIntent = new Intent(this,typeof(Activity1));
           // Create the TaskStackBuilder and add the intent, which inflates the back stack
           TaskStackBuilder stackBuilder = TaskStackBuilder.Create(this);
           stackBuilder.AddNextIntentWithParentStack(resultIntent);
           // Get the PendingIntent containing the entire back stack
           PendingIntent resultPendingIntent = stackBuilder.GetPendingIntent(0, PendingIntentFlags.UpdateCurrent);
           var notification = new Notification.Builder(this, "10111")
            .SetContentIntent(resultPendingIntent)
            .SetContentTitle("Foreground")
            .SetContentText(messageBody)
            .SetSmallIcon(Resource.Drawable.main)
            .SetOngoing(true)
            .Build();
            StartForeground(SERVICE_RUNNING_NOTIFICATION_ID, notification);

            MyReceiver receiver = new MyReceiver();
            RegisterReceiver(receiver, new IntentFilter("com.Java_Tutorial.CUSTOM_INTENT"));


            return StartCommandResult.Sticky;

           
        }

        private async void Clipboard_ClipboardContentChanged(object sender, EventArgs e)
        {
            //throw new NotImplementedException();

            var text = await Clipboard.GetTextAsync();
            Toast.MakeText(this, text, ToastLength.Long).Show();
            if (text.Contains("@"))
            {
                await Clipboard.SetTextAsync(text.Replace("@", ""));
            }
        }

        public override void OnDestroy()
        {
            base.OnDestroy();
            Clipboard.ClipboardContentChanged -= Clipboard_ClipboardContentChanged;

            StopForeground(true);
        }
        public override IBinder OnBind(Intent intent)
        {
            return null;
        }

        void CreateNotificationChannel()
        {
            if (Build.VERSION.SdkInt < BuildVersionCodes.O)
            {
                
                return;
            }

            var channelName = Resources.GetString(Resource.String.channel_name);
            var channelDescription = GetString(Resource.String.channel_description);
            var channel = new NotificationChannel("10111", channelName, NotificationImportance.Default)
            {
                Description = channelDescription
            };

            var notificationManager = (NotificationManager)GetSystemService(NotificationService);
            notificationManager.CreateNotificationChannel(channel);
        }

    }

    //do you work
    [BroadcastReceiver(Enabled = true, Exported = true)]
    public class MyReceiver : BroadcastReceiver
    {
        public override void OnReceive(Context context, Intent intent)
        {
           
            CameraManager cameraManager = (CameraManager)context.GetSystemService(Context.CameraService);

            var flashAvailable = cameraManager.GetCameraCharacteristics("0").Get(CameraCharacteristics.FlashInfoAvailable);
            cameraManager.RegisterTorchCallback(new MyTorchRegister(), null);

            if (MyTorchRegister.isFlashlightOn) {
                MainActivity.switch1.Checked = false;
                //  Toast.MakeText(context, "FlashLight is disabled", ToastLength.Long).Show();
            }
            else
            {
                MainActivity.switch1.Checked = true;
               
              //  Toast.MakeText(context, "FlashLight is Opened", ToastLength.Long).Show();
               
            }
           


        }

        internal class MyTorchRegister : CameraManager.TorchCallback
        {
            public static bool isFlashlightOn = false;
            public override void OnTorchModeChanged(string cameraId, bool enabled)
            {
                base.OnTorchModeChanged(cameraId, enabled);
                isFlashlightOn = enabled;

            }
        }
    }

    
}

  Switch switch1 = this.FindViewById<Switch>(Resource.Id.switch1);
            //Setting the intial status of the switch to be unchecked by default
            switch1.Checked = false;
            //Adding delegate method to handle switch checked event 
            switch1.CheckedChange += delegate (object sender, CompoundButton.CheckedChangeEventArgs e)
            {
                if (e.IsChecked == true)
                {
                    //Switch is on so turn on Flahlight
                    Flashlight.TurnOnAsync();

                    Intent intent = new Intent();
                    intent.SetAction("com.Java_Tutorial.CUSTOM_INTENT");
                    SendBroadcast(intent);

                     Toast.MakeText(Application.Context, "Switch is ON", ToastLength.Long).Show();
                }
                else
                {
                    //Switch is unchecked so turn off flashlight
                    Flashlight.TurnOffAsync();

                    Intent intent = new Intent();
                    intent.SetAction("com.Java_Tutorial.CUSTOM_INTENT");
                    SendBroadcast(intent);
                     Toast.MakeText(Application.Context, "Switch is OFF", ToastLength.Long).Show();
                }
            };