Xamarin.Android Camera Touch to Focus

Question

I am using Xamarin.Android to use inbuilt camera app to take a photo but there are two missed things that I cant do and I have been googling them for long time:

I want to get a msg or popup (anything) after pressing the button to take a photo like "photo taken"
I want to let the user focus on any point of the camera - TAP TO FOCUS

async void TakePhotoButtonTapped(object sender, EventArgs e)
{
    camera.StopPreview();
    Android.Hardware.Camera.Parameters parameters = camera.GetParameters();
    parameters.FocusMode = global::Android.Hardware.Camera.Parameters.FocusModeAuto;
    camera.SetParameters(parameters);
    var image = textureView.Bitmap;
    try
    {
        var absolutePath = Android.OS.Environment.GetExternalStoragePublicDirectory(Android.OS.Environment.DirectoryDcim).AbsolutePath;
        var folderPath = absolutePath + "/Camera";
        var filePath = System.IO.Path.Combine(folderPath, string.Format("photo_{0}.jpg", Guid.NewGuid()));
        var fileStream = new FileStream(filePath, FileMode.Create);
        await image.CompressAsync(Bitmap.CompressFormat.Jpeg, 92, fileStream);
        fileStream.Close();
        image.Recycle();
        var intent = new Android.Content.Intent(Android.Content.Intent.ActionMediaScannerScanFile);
        var file = new Java.IO.File(filePath);
        var uri = Android.Net.Uri.FromFile(file);
        intent.SetData(uri);
        MainActivity.Instance.SendBroadcast(intent);
    }
    catch (Exception ex)
    {
        System.Diagnostics.Debug.WriteLine(@"               ", ex.Message);
    }
    camera.StartPreview();
}

I tried this but not working:

public void OnAutoFocus(bool success, Android.Hardware.Camera camera)
{
    var parameters = camera.GetParameters();
    if (parameters.FocusMode != Android.Hardware.Camera.Parameters.FocusModeContinuousPicture)
    {
        parameters.FocusMode = Android.Hardware.Camera.Parameters.FocusModeContinuousPicture;
        if (parameters.MaxNumFocusAreas > 0)
        {
            parameters.FocusAreas = null;
        }
        camera.SetParameters(parameters);
        camera.StartPreview();
    }
}
public bool OnTouch(Android.Views.View view, MotionEvent e)
{
    if (camera != null)
    {
        var parameters = camera.GetParameters();
        camera.CancelAutoFocus();
        Rect focusRect = CalculateTapArea(e.GetX(), e.GetY(), 1f);
        if (parameters.FocusMode != Android.Hardware.Camera.Parameters.FocusModeAuto)
        {
            parameters.FocusMode = Android.Hardware.Camera.Parameters.FocusModeAuto;
        }
        if (parameters.MaxNumFocusAreas > 0)
        {
            List<Area> mylist = new List<Area>();
            mylist.Add(new Android.Hardware.Camera.Area(focusRect, 1000));
            parameters.FocusAreas = mylist;
        }
        try
        {
            camera.CancelAutoFocus();
            camera.SetParameters(parameters);
            camera.StartPreview();
            camera.AutoFocus(this);
        }
        catch (System.Exception ex)
        {
            Console.WriteLine(ex.ToString());
            Console.Write(ex.StackTrace);
        }
        return true;
    }
    return false;
}
private Rect CalculateTapArea(object x, object y, float coefficient)
{
    var focusAreaSize = 500;
    int areaSize = Java.Lang.Float.ValueOf(focusAreaSize * coefficient).IntValue();
    int left = clamp((int) x - areaSize / 2, 0, textureView.Width - areaSize);
    int top = clamp((int) y - areaSize / 2, 0, textureView.Height - areaSize);
    RectF rectF = new RectF(left, top, left + areaSize, top + areaSize);
    Matrix.MapRect(rectF);
    return new Rect((int) System.Math.Round(rectF.Left), (int) System.Math.Round(rectF.Top), (int) System.Math.Round(rectF.Right),
        (int) System.Math.Round(rectF.Bottom));
}
private int clamp(int x, int min, int max)
{
    if (x > max)
    {
        return max;
    }
    if (x < min)
    {
        return min;
    }
    return x;
}

To notify the user (point 1) that the photo is taken you can use Toast, refer https://developer.xamarin.com/api/type/Android.Widget.Toast/ for more info. — Leslie Correa, Jan 28 '19 at 13:54
Here is a discussion may be helpful for you .(https://stackoverflow.com/questions/40900263/tap-to-focus-for-camera-implementation) — Junior Jiang, Jan 31 '19 at 01:58

score 0 · Answer 1 · answered Jan 28 '19 at 14:14

0

For focusing the camera when touching the preview you will need to:

Add a touch event handler to listen for the user touching the preview
Get the X and Y coordinates from that touch event, which are usually in the event arguments
Create a rectangle to focus to tell the Android Camera where to focus and in which area
Set FocusAreas and MeteringAreas on Camera.Parameters from your rectangle
Set the new Camera.Parameters on the camera
Set a AutoFocus callback on the camera
When the callback triggers, remove the callback from the camera, and cancel auto focus

To notify the user about a picture being taken, you can use a Toast or create a area in your preview where you want to show such messages. It is entirely up to you how you want to notify the user.

answered Jan 28 '19 at 14:14

Cheesebaron

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i have tried something but it didnt work and i am still fresh with xamarin – Hani Gerges Jan 28 '19 at 14:33
i cant add it here, i dont know how to post it – Hani Gerges Jan 28 '19 at 14:33
i added it as an answer , can you see it ? – Hani Gerges Jan 28 '19 at 14:44
You shouldn't add it as an answer, edit your question and add it there. – Cheesebaron Jan 28 '19 at 14:44
my camera is in a AXML file named CameraLayout.AXML and camera appear in TextureView with ID textureView and i have 2 button 1 for flash and 1 for take photo – Hani Gerges Jan 28 '19 at 14:46
i added it as a comment – Hani Gerges Jan 28 '19 at 14:52
you got it sir ? – Hani Gerges Jan 28 '19 at 15:01
i dont know , when i tab or touch the camera nothing happen and – Hani Gerges Jan 28 '19 at 20:04
camera.AutoFocus(this); in this line i get issue – Hani Gerges Jan 28 '19 at 20:04
CheeseBaron any help ? – Hani Gerges Jan 30 '19 at 10:31

Xamarin.Android Camera Touch to Focus

1 Answers1