Change the size of a fragment with a button

I'm trying to change the weight of "MapView" and "InfoContent" when i click on a button inside the mapview fragment. The mapView Fragment is defined in the PlaceholderFragment2 Java Class. The first click should change the weight to a new value, while the second click should restore the old value.

XMl:

<LinearLayout xmlns:android="http://ift.tt/nIICcg"
xmlns:tools="http://ift.tt/LrGmb4"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
tools:context=".MainActivity" 
android:orientation="vertical"
>

<FrameLayout
    android:id="@+id/TitleBar"
    android:layout_width="fill_parent"
    android:layout_height="50dp" 
    >
</FrameLayout>

<FrameLayout
    android:id="@+id/MapView"
    android:layout_width="fill_parent"
    android:layout_height="0dp" 
    android:layout_weight="1">
</FrameLayout>

<FrameLayout
    android:id="@+id/InfoTitleBar"
    android:layout_width="fill_parent"
    android:layout_height="170dp" 
    >
</FrameLayout>

<FrameLayout
    android:id="@+id/InfoContent"
    android:layout_width="fill_parent"
    android:layout_height="0dp"
    android:layout_weight="0" 
    >
</FrameLayout></LinearLayout>

MainActivity.Java

public class MainActivity extends Activity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    PlaceholderFragment frg=new PlaceholderFragment();
    PlaceholderFragment2 frg2=new PlaceholderFragment2();
    PlaceholderFragment3 frg3=new PlaceholderFragment3();
    PlaceholderFragment4 frg4=new PlaceholderFragment4();

    FragmentManager manager=getFragmentManager();
    FragmentTransaction transaction=manager.beginTransaction();

    transaction.add(R.id.TitleBar, frg, "Frag_Top_tag");
    transaction.add(R.id.MapView, frg2, "Frag_Middle_tag");
    transaction.add(R.id.InfoTitleBar, frg3, "Frag_Bottom_tag");
    transaction.add(R.id.InfoContent, frg4, "Frag_Content_tag");

    transaction.commit();
}

And PlaceHolderFragment2.java

public static class PlaceholderFragment2 extends Fragment {

    public PlaceholderFragment2() {
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.mapview, container,
                false);

        final Button button = 
                 (Button) rootView.findViewById(R.id.zoomMap);
            button.setOnClickListener(new View.OnClickListener() {
                public void onClick(View v) {
                    buttonClicked(v);
                }
            });

        return rootView;
    }