Why doesn't my TabListener work?

Question

I wanted to implement tabs and a tablistener to my app.

    public class MyActivity extends Activity {

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

        final ActionBar actionBar = getActionBar();
        actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);

        ActionBar.Tab tabA = actionBar.newTab();
        tabA.setText("Tab A");
        tabA.setTabListener(new TabListener<Tab1>(this, "Tag A", Tab1.class));
        actionBar.addTab(tabA);

        Tab tabB = actionBar.newTab();
        tabB.setText("Tab B");
        tabB.setTabListener(new TabListener<Tab2>(this, "Tag B", Tab2.class));
        actionBar.addTab(tabB);

        Tab tabC = actionBar.newTab();
        tabC.setText("Tab C");
        tabC.setTabListener(new TabListener<Tab3>(this, "Tag C", Tab3.class));
        actionBar.addTab(tabC);

        if (savedInstanceState != null) {
            int savedIndex = savedInstanceState.getInt("SAVED_INDEX");
            getActionBar().setSelectedNavigationItem(savedIndex);
        }

    }

    @Override
    protected void onSaveInstanceState(Bundle outState) {
        // TODO Auto-generated method stub
        super.onSaveInstanceState(outState);
        outState.putInt("SAVED_INDEX", getActionBar().getSelectedNavigationIndex());
    }

}

But i get an NullPointerException from this line:

actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);

Could somebody tell me why and what to do?

I will add the other classes and the StackTrace if needed.

Answer 1

getActionBar() returns null. Do check the manifest if you applied a non action bar theme. If so change the theme so that the activity has actiobar.

public ActionBar getActionBar ()

Added in API level 11 Retrieve a reference to this activity's ActionBar.

Returns The Activity's ActionBar, or null if it does not have one

Answer 2

Which theme are you using? Check if theme is Theme.NoTitleBar in Manifest. If so, change it to ie Theme.Holo.