using a generic class in android

Hi i am new to android.. i have the following code..

package squash.trainer;
import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;

public class SquashTrainerActivity extends Activity {
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
         // Button btn_start = (Button) findViewById(R.id.btn_start);
        //btn_start.setOnClickListener(new View.OnClickListener() {
        //      public void onClick(View v) {
        //      setContentView(R.layout.selecttopmenu);

        //      }});          
}
public boolean onCreateOptionsMenu(Menu menu) { 
    MenuInflater inflater = getMenuInflater(); 
    inflater. inflate(R.menu.mainmenu, menu); 
    return true; 
 }
public boolean onOptionsItemSelected(MenuItem item) { 

        switch (item. getItemId() ) { 

        case R. id.btn1: 
            BugsSequence();
                        return true; 
        case R. id.btn2: 

                        return true; 
        case R. id.btn3: 

                        return true; 
        case R. id.btn4: 

                        return true; 
                    default: 
                return super. onOptionsItemSelected(item) ; 
        }    
}
private void BugsSequence() {
    // TODO Auto-generated method stub
}
}

for each case i want to use the a class to load the new layout and logic...

currently i have a test class called Bugssequence

package squash.trainer;
import android.os.Bundle;
import android.app.Activity;
//import android.view.View;
//import android.widget.Button;

public class BugsSequence extends Activity {
        @Override
public void onCreate(Bundle savedInstanceState) {
        //super.onCreate(savedInstanceState);
        setContentView(R.layout.selecttopmenu);   
}
/**
 * @param args
 */
public static void main(String[] args) {
    //
}

}

How can i get it load the new layout.. when i press on button 1.. it does nothing.. or is there a better way to load 4 different layouts /class(logic) one for each of the menus. Should i开发者_如何学JAVA even be creating new activities for each screen / layout ?

Thanks you for your assistance...

Complete guide can be found here: http://developer.android.com/guide/topics/fundamentals/activities.html

At first, your activity should be declared in the manifest

    <activity android:name=".YourActivity"
              android:label="@string/youractivitylabel">
        <intent-filter>
            <action android:name="android.intent.action.VIEW" />
            <category android:name="android.intent.category.DEFAULT" />
        </intent-filter>
    </activity>

and then you can start YourActivity from code:

Intent intent = new Intent(this, YourActivity.class);
startActivity(intent);

You can put easily some extra data into the intent and/or start it for a result

startActivityForResult(intent, PICK_CONTACT_REQUEST);

Read the link above, it's very useful!