ActivityGroup

package com.example.myandroid;

import java.util.ArrayList;

import android.app.ActivityGroup;
import android.content.Intent;
import android.os.Bundle;
import android.view.KeyEvent;
import android.view.View;

public class FirstGroup extends ActivityGroup {

// Keep this in a static variable to make it accessible for all the nested activities, lets them manipulate the view
public static FirstGroup group;

// Need to keep track of the history if you want the back-button to work properly, don't use this if your activities requires a lot of memory.
private ArrayList history;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
this.history = new ArrayList();
group = this;

// Start the root activity withing the group and get its view
View view = getLocalActivityManager().startActivity("CitiesActivity", new
Intent(this,CitiesActivity.class)
.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP))
.getDecorView();

// Replace the view of this ActivityGroup
replaceView(view);

}

public void replaceView(View v) {
// Adds the old one to history
history.add(v);
// Changes this Groups View to the new View.
setContentView(v);
}

public void back() {
if(history.size() > 0) {
history.remove(history.size()-1);
setContentView(history.get(history.size()-1));
}else {
finish();
}
}

// public void onBackPressed() {
// FirstGroup.group.back();
// return;
// }
@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
// TODO Auto-generated method stub
if(keyCode==KeyEvent.KEYCODE_BACK){
back();
return true;
}else

return super.onKeyDown(keyCode, event);
}
}






Add Code:
View view = FirstGroup.group.getLocalActivityManager()
.startActivity("show_city", i
.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP))
.getDecorView();

// Again, replace the view
FirstGroup.group.replaceView(view);