Android Signature Capture [closed]

Answer 1

I know this is an old question, but I needed to implement my own view to capture the signature because I am using MonoForAndroid (C# not Java). So I am adding my View code in here in case somebody needs it.

using System;
using Android.Content;
using Android.Graphics;
using Android.Views;

namespace MyApp.Views
{
    public class CaptureSignatureView : View
    {
        public CaptureSignatureView(Context c, SignatureData signatureData) : base(c)
        {
            SignatureData = signatureData;
            _Path = new Path();
            _BitmapPaint = new Paint(PaintFlags.Dither);
            _paint = new Paint
            {
                AntiAlias = true,
                Dither = true,
                Color = Color.Argb(255, 0, 0, 0)
            };
            _paint.SetStyle(Paint.Style.Stroke);
            _paint.StrokeJoin = Paint.Join.Round;
            _paint.StrokeCap = Paint.Cap.Round;
            _paint.StrokeWidth = 8;
        }

        protected override void OnSizeChanged(int w, int h, int oldw, int oldh)
        {
            base.OnSizeChanged(w, h, oldw, oldh);
            _Bitmap = Bitmap.CreateBitmap(w, (h > 0 ? h : ((View)this.Parent).Height), Bitmap.Config.Argb8888);
            _Canvas = new Canvas(_Bitmap);
        }

        protected override void OnDraw(Canvas canvas)
        {
            canvas.DrawColor(Color.White);
            canvas.DrawBitmap(_Bitmap, 0, 0, _BitmapPaint);
            canvas.DrawPath(_Path, _paint);
        }

        private float _mX, _mY;
        private const float TouchTolerance = 4;

        private void TouchStart(float x, float y)
        {
            _Path.Reset();
            _Path.MoveTo(x, y);
            _mX = x;
            _mY = y;
            SignatureData.AddPoint(SignatureState.Start, (int)x, (int)y);
        }

        private void TouchMove(float x, float y)
        {
            float dx = Math.Abs(x - _mX);
            float dy = Math.Abs(y - _mY);

            if (dx >= TouchTolerance || dy >= TouchTolerance)
            {
                _Path.QuadTo(_mX, _mY, (x + _mX) / 2, (y + _mY) / 2);
                SignatureData.AddPoint(SignatureState.Move, (int)x, (int)y);
                _mX = x;
                _mY = y;
            }
        }

        private void TouchUp()
        {
            if (!_Path.IsEmpty)
            {
                _Path.LineTo(_mX, _mY);
                _Canvas.DrawPath(_Path, _paint);
            }
            else
            {
                _Canvas.DrawPoint(_mX, _mY, _paint);
            }
            SignatureData.AddPoint(SignatureState.End, (int)_mX, (int)_mY);

            _Path.Reset();
        }

        public override bool OnTouchEvent(MotionEvent e)
        {
            var x = e.GetX();
            var y = e.GetY();

            switch (e.Action)
            {
                case MotionEventActions.Down:
                    TouchStart(x, y);
                    Invalidate();
                    break;
                case MotionEventActions.Move:
                    TouchMove(x, y);
                    Invalidate();
                    break;
                case MotionEventActions.Up:
                    TouchUp();
                    Invalidate();
                    break;
            }
            return true;
        }

        public void ClearCanvas()
        {
            _Canvas.DrawColor(Color.White);
            Invalidate();
        }

        public Bitmap CanvasBitmap()
        {
            return _Bitmap;
        }

        public void Clear()
        {
            ClearCanvas();
            SignatureData = new SignatureData();
        }

        #region Implementation

        private Bitmap _Bitmap;
        private Canvas _Canvas;
        private readonly Path _Path;
        private readonly Paint _BitmapPaint;
        private readonly Paint _paint;
        public  SignatureData SignatureData;

        #endregion
    }

}

Also, I have a blog post here that goes through the details of how to capture the signature. Basically you can do it in two different ways. Either you capture the view with the signature as an image and you save that bitmap (and send it to the server maybe). Or you could just capture a two dimensional array of points and reconstruct the signature in any way you want it.