App crashed on FragmentTransaction

Question

everybody. My app crashed and I don't know why. I'm recently learning FragmentTransaction. Basically, activity_main.xml contains my ActionBar with two tabs containing two fragments, BasicFragment and BFragment. I want BasicFragment to dynamically show a fragment. Can somebody please enlighten me what went wrong here? Thank you.

activity_main.xml:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context=".MainActivity" >

<LinearLayout
    android:id="@+id/fragment_container"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >
</LinearLayout>

</LinearLayout>

MainActivity.java:

public class MainActivity extends Activity {

public static Context appContext;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    actionBar();
    FragmentManager fragmentManager = getFragmentManager();
    FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
    BasicFragment fragmentee = new BasicFragment();
    fragmentTransaction.add(R.id.afrag_container, fragmentee);
    fragmentTransaction.commit();
}

private void actionBar() {
    // TODO Auto-generated method stub
    appContext = getApplicationContext();

    // ActionBar
    ActionBar actionbar = getActionBar();
    actionbar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);

    actionbar.setDisplayShowTitleEnabled(false);

    ActionBar.Tab PlayerTab = actionbar.newTab().setText("Fragment A");
    ActionBar.Tab StationsTab = actionbar.newTab().setText("Fragment B");

    Fragment PlayerFragment = new BasicFragment();
    Fragment StationsFragment = new BFragment();

    PlayerTab.setTabListener(new TabListener(PlayerFragment));
    StationsTab.setTabListener(new TabListener(StationsFragment));

    actionbar.addTab(PlayerTab);
    actionbar.addTab(StationsTab);
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    MenuInflater inflater = getMenuInflater();
    inflater.inflate(R.menu.menu_pow, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId()) {
    case R.id.menuitem_search:
        Toast.makeText(appContext, "search", Toast.LENGTH_SHORT).show();
        return true;
    case R.id.menuitem_add:
        Toast.makeText(appContext, "add", Toast.LENGTH_SHORT).show();
        return true;
    }
    return false;
}

@Override
protected void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
    outState.putInt("tab", getActionBar().getSelectedNavigationIndex());
}

}

class TabListener implements ActionBar.TabListener { public Fragment fragment;

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

@Override
public void onTabReselected(Tab tab, FragmentTransaction ft) {
    Toast.makeText(MainActivity.appContext, "Reselected!",
            Toast.LENGTH_LONG).show();
}

@Override
public void onTabSelected(Tab tab, FragmentTransaction ft) {
    ft.replace(R.id.fragment_container, fragment);
}

@Override
public void onTabUnselected(Tab tab, FragmentTransaction ft) {
    ft.remove(fragment);
}

}

BasicFragment.java:

public class BasicFragment extends Fragment {

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    View view = inflater.inflate(R.layout.examplefragment, container, false);
    return view;
}

}

afragment.xml:

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

<FrameLayout
    android:id="@+id/afrag_container"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />

</LinearLayout>

examplefragment.xml:

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

<Button android:id="@+id/butt1"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:text="HI!" />

</LinearLayout>

Answer 1

In your Main activity you are trying to access a linear layout which is in afragment.xml, so is the error. Main activity is displaying the layout activity_main.xml, change the afrag_container to fragment_container(Linear layout) which is in activity_main.xml.