Android App - How to save a bitmap drawing on canvas as image? Check code?

Android App - How to save a bitmap drawing on canvas as image? Check code?

I tried to use the following codes to
Draw on canvas
Save the canvas on Image
Problem - When I try to save the image, it shows a null pointer error and
nothing is saved.
Please help me to find the problem with the code or suggest me an
alternative, which does excatly the same. Thanks in advance.
Code to draw on canvas:
package com.example.drawapp_new;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
public class MyDrawViewNew extends View {
private Bitmap mBitmap;
private Canvas mCanvas;
private Path mPath;
private Paint mBitmapPaint;
private Paint mPaint;
public MyDrawViewNew(Context c, AttributeSet attrs) {
super(c, attrs);
mPath = new Path();
mBitmapPaint = new Paint(Paint.DITHER_FLAG);
mPaint = new Paint();
mPaint.setAntiAlias(true);
mPaint.setDither(true);
mPaint.setColor(0xFF000000);
mPaint.setStyle(Paint.Style.STROKE);
mPaint.setStrokeJoin(Paint.Join.ROUND);
mPaint.setStrokeCap(Paint.Cap.ROUND);
mPaint.setStrokeWidth(9);
}
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
mBitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
mCanvas = new Canvas(mBitmap);
}
@Override
protected void onDraw(Canvas canvas) {
canvas.drawBitmap(mBitmap, 0, 0, mBitmapPaint);
canvas.drawPath(mPath, mPaint);
}
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;
}
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 clear(){
mBitmap.eraseColor(Color.GREEN);
invalidate();
System.gc();
}
}
Second code to save the canvas as image is in main activity.
I tried a few things and some part of the code is commented.
Since I am a beginner, I appreciate any advice
Second code MainActivity:
package com.example.draw2;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import android.app.Activity;
import android.os.Bundle;
import android.os.Environment;
import android.view.Menu;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;
public class MainActivity extends Activity
{
MyDrawView myDrawView;
//FileService file;
//TextView hello;
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
myDrawView = new MyDrawView(this, null);
setContentView(R.layout.activity_main);
Button button1 = (Button)findViewById(R.id.button1);
button1.setOnClickListener(new View.OnClickListener()
{
public void onClick(View v)
{
//View content = myDrawView;
//System.out.println(content);
//Bitmap bitmap = content.getDrawingCache();
File folder = new
File(Environment.getExternalStorageDirectory().toString());
boolean success = false;
if (!folder.exists())
{
success = folder.mkdirs();
}
System.out.println(success+"folder");
File file = new
File(Environment.getExternalStorageDirectory().toString()
+ "/sample.JPEG");
if ( !file.exists() )
{
try {
success = file.createNewFile();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
System.out.println(success+"file");
// File f = new
File(Environment.getExternalStoragePublicDirectory(
// Environment.DIRECTORY_PICTURES),"YYYimage.png");
//System.out.println(file);
/*
* try {
f.createNewFile();
} catch (IOException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
*/
FileOutputStream ostream = null;
try
{
ostream = new FileOutputStream(file);
System.out.println(ostream);
//bitmap.compress(Bitmap.CompressFormat.PNG, 100, ostream);
ostream.flush();
ostream.close();
}catch (NullPointerException e)
{
e.printStackTrace();
Toast.makeText(getApplicationContext(), "Null error",
Toast.LENGTH_SHORT).show();
}
catch (FileNotFoundException e)
{
e.printStackTrace();
Toast.makeText(getApplicationContext(), "File error",
Toast.LENGTH_SHORT).show();
}
catch (IOException e)
{
e.printStackTrace();
Toast.makeText(getApplicationContext(), "IO error",
Toast.LENGTH_SHORT).show();
}
}
});
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is
present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
}