package com.calindora.tracker;

import android.app.Activity;
import android.os.Bundle;

public class TrackerActivity extends Activity
{
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
    }
}

package com.calindora.tracker;

import android.app.Activity;
import android.os.Bundle;

public class TrackerActivity extends Activity
{
    /** Called when the activity is first created. */
    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
    }
}

Change onCreate from public to protected in TrackerActivity.