In my android application user do signature in the form in my app. the signature has to be edit , cleer, save. i do save and clear. but edit not work i used code below
mContent = (LinearLayout) findViewById(R.id.linearLayout);
mSignature = new signature(this, null);
mSignature.setBackgroundColor(Color.WHITE);
mContent.addView(mSignature, LayoutParams.FILL_PARENT, LayoutParams.FILL_PARENT);
mClear = (Button)findViewById(R.id.clear);
mGetSign = (Button)findViewById(R.id.getsign);
mGetSign.setEnabled(false);
mCancel = (Button)findViewById(R.id.cancel);
mView = mContent;
mClear.setOnClickListener(new OnClickListener() 
    {        
        public void onClick(View v) 
        {
            Log.v("log_tag", "Panel Cleared");
            mSignature.clear();
            mGetSign.setEnabled(false);
        }
    });
    mGetSign.setOnClickListener(new OnClickListener() 
    {        
        public void onClick(View v) 
        {
            Log.v("log_tag", "Panel Saved");
                mView.setDrawingCacheEnabled(true);
                mSignature.save(mView);
                Bundle b = new Bundle();
                b.putString("status", "done");
                b.putParcelable("data", mBitmap);
                Intent intent = new Intent();
                intent.putExtras(b);
                setResult(RESULT_OK,intent);   
                finish();
            }
    });
    mCancel.setOnClickListener(new OnClickListener() 
    {        
        public void onClick(View v) 
        {
            Log.v("log_tag", "Panel Canceled");
            Bundle b = new Bundle();
            b.putString("status", "cancel");
            Intent intent = new Intent();
            intent.putExtras(b);
            setResult(RESULT_OK,intent);  
            finish();
        }
    });
}
@Override
protected void onDestroy() {
    Log.w("GetSignature", "onDestory");
    super.onDestroy();
}
public class signature extends View 
    {
        private static final float STROKE_WIDTH = 5f;
        private static final float HALF_STROKE_WIDTH = STROKE_WIDTH / 2;
        private Paint paint = new Paint();
        private Path path = new Path();
        private float lastTouchX;
        private float lastTouchY;
        private final RectF dirtyRect = new RectF();
        public signature(Context context, AttributeSet attrs) 
        {
            super(context, attrs);
            paint.setAntiAlias(true);
            paint.setColor(Color.BLACK);
            paint.setStyle(Paint.Style.STROKE);
            paint.setStrokeJoin(Paint.Join.ROUND);
            paint.setStrokeWidth(STROKE_WIDTH);
        }
        public void save(View v) 
        {
            Log.v("log_tag", "Width: " + v.getWidth());
            Log.v("log_tag", "Height: " + v.getHeight());
            if(mBitmap == null)
            {
                mBitmap =  Bitmap.createBitmap (mContent.getWidth(), mContent.getHeight(), Bitmap.Config.RGB_565);;
            }
            Canvas canvas = new Canvas(mBitmap);
            try
            {
                FileOutputStream mFileOutStream = new FileOutputStream(mypath);
                v.draw(canvas); 
                mBitmap.compress(Bitmap.CompressFormat.PNG, 90, mFileOutStream); 
                mFileOutStream.flush();
                mFileOutStream.close();
               // String url = Images.Media.insertImage(getContentResolver(), mBitmap, "title", null);
               // Log.v("log_tag","url: " + url);
                //In case you want to delete the file
                //boolean deleted = mypath.delete();
                //Log.v("log_tag","deleted: " + mypath.toString() + deleted);
                //If you want to convert the image to string use base64 converter
            }
            catch(Exception e) 
            { 
                Log.v("log_tag", e.toString()); 
            } 
        }
        public void clear() 
        {
            path.reset();
          invalidate();
        }
        @Override
        protected void onDraw(Canvas canvas) 
        {
            canvas.drawPath(path, paint);
        }
        @Override
        public boolean onTouchEvent(MotionEvent event) 
        {
            float eventX = event.getX();
            float eventY = event.getY();
            mGetSign.setEnabled(true);
            switch (event.getAction()) 
            {
            case MotionEvent.ACTION_DOWN:
                path.moveTo(eventX, eventY);
                lastTouchX = eventX;
                lastTouchY = eventY;
                return true;
            case MotionEvent.ACTION_MOVE:
            case MotionEvent.ACTION_UP:
                resetDirtyRect(eventX, eventY);
                int historySize = event.getHistorySize();
                for (int i = 0; i < historySize; i++) 
                {
                    float historicalX = event.getHistoricalX(i);
                    float historicalY = event.getHistoricalY(i);
                    expandDirtyRect(historicalX, historicalY);
                    path.lineTo(historicalX, historicalY);
                }
                path.lineTo(eventX, eventY);
                break;
            default:
                debug("Ignored touch event: " + event.toString());
                return false;
            }
            invalidate((int) (dirtyRect.left - HALF_STROKE_WIDTH),
                    (int) (dirtyRect.top - HALF_STROKE_WIDTH),
                    (int) (dirtyRect.right + HALF_STROKE_WIDTH),
                    (int) (dirtyRect.bottom + HALF_STROKE_WIDTH));
            lastTouchX = eventX;
            lastTouchY = eventY;
            return true;
        }
        private void debug(String string){
        }
        private void expandDirtyRect(float historicalX, float historicalY) 
        {
            if (historicalX < dirtyRect.left) 
            {
                dirtyRect.left = historicalX;
            } 
            else if (historicalX > dirtyRect.right) 
            {
                dirtyRect.right = historicalX;
            }
            if (historicalY < dirtyRect.top) 
            {
                dirtyRect.top = historicalY;
            } 
            else if (historicalY > dirtyRect.bottom) 
            {
                dirtyRect.bottom = historicalY;
            }
        }
        private void resetDirtyRect(float eventX, float eventY) 
        {
            dirtyRect.left = Math.min(lastTouchX, eventX);
            dirtyRect.right = Math.max(lastTouchX, eventX);
            dirtyRect.top = Math.min(lastTouchY, eventY);
            dirtyRect.bottom = Math.max(lastTouchY, eventY);
        }
    }