SingleFragmentActivity.java

package criminalintent.android.bignerdranch.com.criminalintent;

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentManager;

public abstract class SingleFragmentActivity extends FragmentActivity {
    protected abstract Fragment createFragment();
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_fragment);
        FragmentManager fm = getSupportFragmentManager();
        Fragment fragment = fm.findFragmentById(R.id.fragmentContainer);
        if (fragment == null) {
            fragment = createFragment();
            fm.beginTransaction()
                    .add(R.id.fragmentContainer, fragment)
                    .commit();
        }
    }
}