package com.bignerdranch.android.beatbox;

import android.support.v4.app.Fragment;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

public class BeatBoxActivity extends SingleFragmentActivity {
    @Override
    protected Fragment createFragment() {
        return BeatBoxFragment.newInstance();
    }
}

package com.bignerdranch.android.beatbox;


import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v7.app.AppCompatActivity;

public abstract class SingleFragmentActivity extends AppCompatActivity {
    protected abstract Fragment createFragment();

    protected int getLayoutResId() {
        return R.layout.activity_fragment;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(getLayoutResId());
        FragmentManager manager = getSupportFragmentManager();
        Fragment fragment = manager.findFragmentById(R.id.fragment_container);

        if (fragment == null) {
            fragment = createFragment();
            manager.beginTransaction()
                .add(R.id.fragment_container, fragment)
                .commit();
        }
    }
}