Maui for Android simulate backspace button action

Haviv Elbsz 1,986 Reputation points
2024-05-24T10:04:01.8433333+00:00

Hello All. in my app I want to simulate backspace button action manly I want when user hold the the button pressed to delete a character in every 300 milliseconds until the button released please how I do that. Thank you.

.NET MAUI
.NET MAUI
A Microsoft open-source framework for building native device applications spanning mobile, tablet, and desktop.
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Accepted answer
  1. Yonglun Liu (Shanghai Wicresoft Co,.Ltd.) 37,421 Reputation points Microsoft Vendor
    2024-05-28T03:03:52.1566667+00:00

    Hello,

    After some investigation, you can achieve this functionality by implementing a listen to the touch event for finger presses and lifts.

    Here is the workaround and sample code.

    First of all, KeyDown will always be triggered in the touch event when the finger is pressed for a long time. Therefore you can accomplish the function of deleting a character every 300ms by initiating a thread when the finger is pressed for a long time.

    When the user is short-pressing, you need to determine the event interval between when the user's finger is pressed and when it is lifted. In this example, if the time interval is less than 300ms, it is treated as a short press and one character is deleted.

    The following is sample code:

    //Implement the OnTouchListener in Android folder
    public class TouchToDelete : Java.Lang.Object, IOnTouchListener
    {
        private EditText editText;
        long lastTimeStamp;//Record the time pressed
        bool isPress;//Determine if you are pressing
        public TouchToDelete(EditText editText)
        {
            this.editText = editText;
        }
        public bool OnTouch(global::Android.Views.View? v, MotionEvent? e)
        {
            if (e.Action == MotionEventActions.Down) {
                isPress = true;
                lastTimeStamp = GetCurrenttimemillis();
                Thread t1 = new Thread(new ThreadStart(delegate
                {                   
                    while (isPress)
                    {
                        if(GetCurrenttimemillis() - lastTimeStamp > 300)
                        {
                            // If the keystroke event exceeds 300ms, one character is deleted every 300ms
                            MainThread.BeginInvokeOnMainThread(() =>
                            {
                                editText.DispatchKeyEvent(new KeyEvent(KeyEventActions.Down, Keycode.Del));
                            });
                            try
                            {
                                Thread.Sleep(300);
                            }
                            catch (Exception ex)
                            {
                                Console.WriteLine(ex);
                            }
                        }
                    }
                }));
                t1.Start();
            }
            else if (e.Action == MotionEventActions.Up)
            {
                if(GetCurrenttimemillis()- lastTimeStamp <= 300)
                {
                    editText.DispatchKeyEvent(new KeyEvent(KeyEventActions.Down, Keycode.Del));
                }
                isPress = false;
            }
            return true;
        }
        private long GetCurrenttimemillis() // Get the current time in milliseconds
        {
            return (long)(DateTime.UtcNow - new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc)).TotalMilliseconds;
        }
    }
    
    // Invoke the Listener in MAUI part.
    protected override void OnHandlerChanged()
            {
                base.OnHandlerChanged();
    #if ANDROID
                var btn = test_backspace.Handler.PlatformView as Android.Widget.Button;
                var edit = test_entry.Handler.PlatformView as Android.Widget.EditText;
                btn.SetOnTouchListener(new TouchToDelete(edit));
     
    #endif
            }
    

    Best Regards,

    Alec Liu.


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