VERY Basic actionbarsherlock tabs with fragments: FragmentTransaction is null in the onTabSelected() method

Question

I'm implementing some code from an example (http://arvid-g.de/12/android-4-actionbar-with-tabs-example) and trying to convert it to work with ActionBarSherlock.

Here is TabActivity.java:

package com.pnet;

import com.actionbarsherlock.app.ActionBar;
import com.actionbarsherlock.app.ActionBar.Tab;
import com.actionbarsherlock.app.SherlockActivity;

import android.content.Context;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentTransaction;
import android.util.Log;
import android.widget.Toast;

public class TabActivity extends SherlockActivity {

    private static String TAG = "TabActivity";
    public static Context appContext;

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.tab_activity);

       //ActionBar gets initiated
        ActionBar actionbar = getSupportActionBar();
      //Tell the ActionBar we want to use Tabs.
        actionbar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
      //initiating both tabs and set text to it.
        ActionBar.Tab PlayerTab = actionbar.newTab().setText("Fragment A");
        ActionBar.Tab StationsTab = actionbar.newTab().setText("Fragment B");

     //create the two fragments we want to use for display content
        Fragment PlayerFragment = new AFragment();
        Fragment StationsFragment = new BFragment();

    //set the Tab listener. Now we can listen for clicks.
        PlayerTab.setTabListener(new MyTabsListener(PlayerFragment));
        StationsTab.setTabListener(new MyTabsListener(StationsFragment));

   //add the two tabs to the actionbar
        actionbar.addTab(PlayerTab);
        actionbar.addTab(StationsTab);
    }

    class MyTabsListener implements ActionBar.TabListener {
        public Fragment fragment;

        public MyTabsListener(Fragment fragment) {
        this.fragment = fragment;
        }

        @Override
        public void onTabSelected(Tab tab, FragmentTransaction ft) {
            // TODO Auto-generated method stub
            if (fragment == null) {
                Log.v(TAG, "fragment is null");
            }

            if (ft == null) {
                Log.v(TAG, "fragment TRANSACTION is null");
            }

            ft.replace(R.id.fragment_container, fragment);          
        }

        @Override
        public void onTabUnselected(Tab tab, FragmentTransaction ft) {
            // TODO Auto-generated method stub

        }

        @Override
        public void onTabReselected(Tab tab, FragmentTransaction ft) {
            // TODO Auto-generated method stub
            Toast.makeText(TabActivity.appContext, "Reselected!", Toast.LENGTH_LONG).show();

        }

    }
}

Here is AFragment.java

package com.pnet;

import com.actionbarsherlock.app.SherlockFragment;

import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

public class AFragment extends SherlockFragment {

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        return inflater.inflate(R.layout.afragment, container, false);
    }

}

Here is BFragment.java

package com.pnet;

import com.actionbarsherlock.app.SherlockFragment;

import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

public class BFragment extends SherlockFragment {

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        return inflater.inflate(R.layout.bfragment, container, false);
    }

}

Here is tab_activity.xml:

<LinearLayout android:layout_gravity="center" android:layout_height="fill_parent" android:layout_width="fill_parent" android:orientation="vertical" xmlns:android="http://schemas.android.com/apk/res/android">
<LinearLayout android:id="@+id/fragment_container" android:layout_height="match_parent" android:layout_width="match_parent">

 </LinearLayout>
</LinearLayout>

Here is afragment.xml:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <TextView xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/text"
    android:layout_width="match_parent" android:layout_height="match_parent"
    android:gravity="center_vertical|center_horizontal"
    android:textAppearance="?android:attr/textAppearanceMedium"
    android:text="@string/hello_world"/>


</LinearLayout>

Here is bfragment.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <TextView xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/text"
    android:layout_width="match_parent" android:layout_height="match_parent"
    android:gravity="center_vertical|center_horizontal"
    android:textAppearance="?android:attr/textAppearanceMedium"
    android:text="@string/tab_navigation_content"/>


</LinearLayout>

When the activity loads it triggers the onTabSelected() method. I put a couple if statements checking objects for null which write to the log and it shows that the FragmentTransaction object is null. Anyone see where I'm going wrong? Thanks.

Solution

You should make your Activity extend from SherlockFragmentActivity instead of SherlockActivity the same way you would use FragmentActivity instead of Activity with support-v4 package

Please have a look at the Fragment sample here: https://github.com/JakeWharton/ActionBarSherlock/tree/master/actionbarsherlock-samples/fragments