Android programming: UI Fragment hosted in Activity

AndroidManifest.xml:

<manifest package="com.solezero.android.learning"

           xmlns:android="http://schemas.android.com/apk/res/android">

    <application

         android:allowBackup="true"

         android:icon="@mipmap/ic_launcher" 

         android:label="@string/app_name" 

         android:supportsRtl="true" 

         android:theme="@style/AppTheme">
        <activity

             android:name=".MyActivity"

             android:label="@string/app_name">
            <intent-filter>
                <action android:name="android.intent.action.MAIN"/>
                <category android:name="android.intent.category.LAUNCHER"/>
            </intent-filter>
        </activity>
    </application>

</manifest>

MyActivity.java:

package com.solezero.android.learning;

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

public class MyActivity extends AppCompatActivity {

    @Override    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_my);

        FragmentManager fragmentManager = getSupportFragmentManager();

        Fragment fragment = fragmentManager.findFragmentById(R.id.fragmentContainer);

        if (fragment == null) {
            fragment = createFragment();

           fragmentManager.beginTransaction().add(R.id.fragmentContainer, fragment).commit();        }
    }

    protected Fragment createFragment() {

        MyFragment myFragment = new MyFragment();

        return myFragment;
    }

}

layout/activity_my.xml:

<?xml version="1.0" encoding="utf-8"?> 

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"

              android:id="@+id/fragmentContainer"

              android:layout_width="match_parent"

              android:layout_height="match_parent" />

MyFragment.java:

package com.solezero.android.learning;

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

public class MyFragment extends Fragment {
    @Override    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

        View view = inflater.inflate(R.layout.fragment_my, container, false);

        return view;
    }
}

To access the Activity from the Fragment, use getActivity().


layout/fragment_my.xml:

<?xml version="1.0" encoding="utf-8"?> 

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

               android:orientation="vertical" 

               android:layout_width="match_parent"

               android:layout_height="match_parent">

</LinearLayout>