Dynamic Background (on LinearLayout) - what is my

Question

I have a problem, I'm trying to get my apps background to change, each ten seconds, based on a timer... I have done what i could and cant work it out as im a beginner to java and programming :) I would love if someone could just correct my code please ;) (I can packgage it into a phone etc eclipse doesnt show an error, but my app force closes, when the timer goes), here it is:

public class CookBookActivity extends Activity {
    /** Called when the activity is first created. */

    private static final long GET_DATA_INTERVAL = 10000;
    int images[] = {R.drawable.smothie1,R.drawable.omletherb1};
    int index = 0;
    ImageView img;
    Handler hand = new Handler();
    private LinearLayout layout;

    public void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        this.setContentView(R.layout.main);
        layout = (LinearLayout)findViewById(R.id.linearLayout1);
        hand.postDelayed(run, GET_DATA_INTERVAL);
    }

    Runnable run = new Runnable() {
        public void run() {
            layout.setBackgroundDrawable(getDrawable(images[index++]));
            if (index == images.length)
                index = 0;
            hand.postDelayed(run, GET_DATA_INTERVAL);


        Typeface tf2 = Typeface.createFromAsset(getAssets(),
                "fonts/BPreplay.otf");
        TextView tv2 = (TextView) findViewById(R.id.textView2);
        tv2.setTypeface(tf2);


        Typeface tf = Typeface.createFromAsset(getAssets(),
                "fonts/BPreplay.otf");
        TextView tv = (TextView) findViewById(R.id.textView1);
        tv.setTypeface(tf);


        Button mainNext = (Button) findViewById(R.id.nextScreen1);
        mainNext.setOnClickListener(new OnClickListener() {
            public void onClick(View v) {
                Intent i = new Intent();
                i.setClassName("com.unKnown.cookbook", "com.unKnown.cookbook.screen1");
                startActivity(i);

            }
        });
        }
    };

    protected Drawable getDrawable(int i) {
        // TODO Auto-generated method stub
        return null;
    }
}

EDIT:

Now I have finnaly solved my problem and my image sets to background (thanks to @Yashwanth Kumar 's help and me :) ), Its almost fine now, but now my it only sets one image as background (each ten seconds it sets the same image), I think it's down to either of two of the following things:

either:

-handler stops (whcich i doubt)- I have now confirmed it works and every swecond it does the procedure, so it's down to second issue

or:

it only uses the first image from the list (R.drawable.omletherb1), in which case I'll have to set something like if R.Drawable.zzz is set then do set image R.drawable.ccc

Please tell me what you think, and here is tyhe code I have now ended up with:

public class CookBookActivity extends Activity { /** Called when the activity is first created. */

private static final long GET_DATA_INTERVAL = 1000;
int images[] = {R.drawable.omletherb1,R.drawable.smothie1};
int index = 0;
LinearLayout img;
Handler hand = new Handler();
private LinearLayout layout;

public void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);
    this.setContentView(R.layout.main);
    layout = (LinearLayout)findViewById(R.layout.main);
    hand.postDelayed(run, GET_DATA_INTERVAL);

    Typeface tf2 = Typeface.createFromAsset(getAssets(),
            "fonts/BPreplay.otf");
    TextView tv2 = (TextView) findViewById(R.id.textView2);
    tv2.setTypeface(tf2);


    Typeface tf = Typeface.createFromAsset(getAssets(),
            "fonts/BPreplay.otf");
    TextView tv = (TextView) findViewById(R.id.textView1);
    tv.setTypeface(tf);


    Button mainNext = (Button) findViewById(R.id.nextScreen1);
    mainNext.setOnClickListener(new OnClickListener() {
        public void onClick(View v) {
            Intent i = new Intent();
            i.setClassName("com.unKnown.cookbook", "com.unKnown.cookbook.screen1");
            startActivity(i);

        }
    });
}

Runnable run = new Runnable() {
    public void run() {
        layout.setBackgroundDrawable(getDrawable(images[index++]));
        if (index == images.length)
            index = 0;
        hand.postDelayed(run, GET_DATA_INTERVAL);

    }
};

protected Drawable getDrawable(int i) {
    // TODO Auto-generated method stub
    return getResources().getDrawable(images[i%2]);
}

}

Answer 1

layout.setBackgroundDrawable(getDrawable(images[index++]));

protected Drawable getDrawable(int i) {
    // TODO Auto-generated method stub
    return null;
}

This is the problem, you are setting null to the background.return some valid drawable and it will work.