Mean of this alert message box in Android

I am creating a simple application in Android. When I compile and run it in the emulator, it's showing an alert box like this; what it does mean?

sorry, The application simplegame (process com.example.simplegame) has stopped unexpectedly. Please try again!

I'm getting this alert box always? Please explain?

UPDATE:

just trying to import a Picture in it,

import android.app.Activity;
import android.os.Bundle;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
imp开发者_如何学运维ort android.graphics.Paint;
import android.graphics.RectF;
import android.graphics.drawable.Drawable;
import android.os.Handler;



public class SimpleGame extends Activity {
    /** Called when the activity is first created. */
    private Bitmap mBackGroundImage;
    private Canvas canvas;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) 
    {
        super.onCreate(savedInstanceState);
        mBackGroundImage = hBitmapFactory(R.drawable.background1);
        canvas.drawBitmap(mBackGroundImage, 0, 0,null);
        setContentView(R.layout.main);
    }

    private Bitmap hBitmapFactory(int background1) 
    {
        // TODO Auto-generated method stub
        return null;
    }
}

am newable to android.thats why getting some troubles.

your application is crashing, there must be some exception in your app. Please check the log .