Hi,

HereI am posting code for Digital Signature.

Create Android project in that

Create MainAct.Class

package com.example.digitalsignatre;

/**
 *  Rahul Baradia
 */

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.os.Bundle;
import android.util.Log;
import android.view.KeyEvent;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup.LayoutParams;
import android.widget.Button;
import android.widget.RelativeLayout;
import android.widget.Toast;

public class MainActivity extends Activity implements OnClickListener {

    public Canvas  mCanvas;   
    private MyView signature;
    private Button saveButton;
    private Button clearButton;

    // onCreate Activity
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        mPaint = new Paint();
        mPaint.setAntiAlias(true);
        mPaint.setDither(true);
        mPaint.setColor(0xFF003F87);
        mPaint.setStyle(Paint.Style.STROKE);
        mPaint.setStrokeJoin(Paint.Join.ROUND);
        mPaint.setStrokeCap(Paint.Cap.ROUND);
        mPaint.setStrokeWidth(3);

        // content view
        signature = new MyView(this);        

        // Dynamically created button on bitmap & canvas       
        RelativeLayout myLayout = new RelativeLayout(this);       
        myLayout.setLayoutParams(new RelativeLayout.LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.FILL_PARENT));
        myLayout.setBackgroundColor(Color.WHITE);

        // For Save Button
        saveButton = new Button(this);
        saveButton.setText("Save");
        saveButton.setOnClickListener(this);

        // For Clear Button
        clearButton = new Button(this);
        clearButton.setText("Clear");
        clearButton.setOnClickListener(this);

        myLayout.addView(signature);
        myLayout.addView(saveButton);
        myLayout.addView(clearButton);

        RelativeLayout.LayoutParams params = new RelativeLayout.LayoutParams(100, LayoutParams.WRAP_CONTENT);
        //Alignments
        params.addRule(RelativeLayout.ALIGN_PARENT_BOTTOM);
        params.addRule(RelativeLayout.ALIGN_PARENT_LEFT);
        saveButton.setLayoutParams(params);

        //Alignments
        RelativeLayout.LayoutParams params2 = new RelativeLayout.LayoutParams(100, LayoutParams.WRAP_CONTENT);
        params2.addRule(RelativeLayout.ALIGN_PARENT_RIGHT);
        params2.addRule(RelativeLayout.ALIGN_PARENT_BOTTOM);
        clearButton.setLayoutParams(params2);

        saveButton.bringToFront();
        clearButton.bringToFront();
        this.setContentView(myLayout);
        new Thread(new RefreshRunner()).start();

        // onclick listner for CLEAR button
        clearButton.setOnClickListener(new OnClickListener() {           
            public void onClick(View v) {
                //Activity for Clearing the Screen
                startActivity(new Intent(MainActivity.this, MainActivity.class));
                finish();
            }
        });
    }

    public Paint mPaint;
    public Bitmap mBitmap;
    public View view;
    public Bitmap b;
    public int w;
    public int h;
    public int Wid;
    public int Ht;

    public void colorChanged(int color) {
        mPaint.setColor(color);
    }

    // Bitmap MyView
    public class MyView extends View implements OnClickListener
    {
        public int height;
        public int width;        
        private Bitmap  mBitmap;       
        private Path    mPath;
        private Paint   mBitmapPaint;

        public MyView(Context c)
        {
            super(c);
            mPath = new Path();
            mBitmapPaint = new Paint(Paint.DITHER_FLAG);  
        }

        @Override
        protected void onSizeChanged(int w, int h, int oldw, int oldh)
        {
            super.onSizeChanged(w, h, oldw, oldh); 
            Wid = w;
            Ht = h;
            mBitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);           
            mCanvas = new Canvas(mBitmap);   


        }

        @Override
        protected void onDraw(final Canvas canvas)
        { try{
            //canvas BG color
            canvas.drawColor(Color.WHITE);   


            canvas.drawPath(mPath, mPaint);
            canvas.drawBitmap(mBitmap, 0, 0, null);

            // onclick listner for SAVE button
            saveButton.setOnClickListener(new OnClickListener() { 
                public void onClick(View v) {
                    //capture the image 
                    try {       
                        //background color of Bitmap
                        Bitmap newBitmap = Bitmap.createBitmap(mBitmap.getWidth(), mBitmap.getHeight(), mBitmap.getConfig());

                        Canvas canvas = new Canvas(newBitmap);
                        canvas.drawColor(Color.WHITE);
                        canvas.drawBitmap(mBitmap, 0, 0, null);

                        newBitmap = Bitmap.createScaledBitmap(newBitmap, 200, 150, true);
                        // Saving the Image
                        saveAsJpg(newBitmap);   
                    } catch (IOException e) {
                        Toast.makeText(getApplicationContext(), e.getMessage(), Toast.LENGTH_LONG).show();
                       
                        e.printStackTrace();
                    }
                } 
            });     
        }catch (Exception e) {Toast.makeText(getApplicationContext(), e.getMessage(), Toast.LENGTH_LONG).show();

       
        e.printStackTrace();
        }
        }

        private float mX, mY;
        private static final float TOUCH_TOLERANCE = 4;

        private void touch_start(float x, float y)
        {
            mPath.reset();
            mPath.moveTo(x, y);
            mX = x;
            mY = y;
            System.out.println("---- " +mX);
        }
        private void touch_move(float x, float y)
        {
            float dx = Math.abs(x - mX);
            float dy = Math.abs(y - mY);
            if (dx >= TOUCH_TOLERANCE || dy >= TOUCH_TOLERANCE) {
                mPath.quadTo(mX, mY, (x + mX)/2, (y + mY)/2);
                mX = x;
                mY = y;
            }
        }
        private void touch_up()
        {
            mPath.lineTo(mX, mY);
            // commit the path to our offscreen
            mCanvas.drawPath(mPath, mPaint);

            // kill this so we don't double draw
            mPath.reset();
        }

        @Override
        public boolean onTouchEvent(MotionEvent event)
        {

            float x = event.getX();
            float y = event.getY();

            switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                touch_start(x, y);
                invalidate();
                break;
            case MotionEvent.ACTION_MOVE:
                touch_move(x, y);
                invalidate();
                break;
            case MotionEvent.ACTION_UP:
                touch_up();
                invalidate();
                break;

            }
            return true;
        }

        public void onClick(View v)
        {
            //In myView
        }
    }

    public void onClick(View v)
    {
        //onCreate
    }
    public static final String DIRECTORY = "/sdcard";
    public static  String signatureImagePath = DIRECTORY+"/signature.png"; 

    // saveAsJpg Method
    public void saveAsJpg(Bitmap b) throws IOException
    {  
        File f= new File(DIRECTORY);
        if(! f.exists())
        {
            f.mkdir();
        }
        FileOutputStream fos = null;
        try { 
            fos = new FileOutputStream(signatureImagePath);
            if(fos != null)
            {     
                b.compress(Bitmap.CompressFormat.PNG, 100, fos );
                Toast.makeText(getApplicationContext(), "Saved to External Memory", Toast.LENGTH_SHORT).show();
                fos.close();
            }
        }catch( NullPointerException e )
        {
            Log.e("testSaveView", "Exception: " + e.toString() );
        }
    }
}


AndroidManifest.xml

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.digitalsignatre"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="15" />
   
   // give permission for external storage
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
   

    <application
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name=".MainActivity"
            android:label="@string/title_activity_main" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

Here is the app image