Android Fragments

Introduction

Introduced in API 11. They are a small piece of UI and must have an Activity. Fragments can be added or removed from the Activity. They allow you to capture the UI functionality where you may need to share it across different activities. If we look at phone vs tablet we might this it more appropriate to use to activities but the UI code will remain the same.

Creating Layout

• Create a subclass of fragment
• Create layout
• Link layout with Fragment
• Place the Fragment inside an Activity

Create a subclass of fragment

We create a subclass of Fragment and override the onCreateView to link the layout with the view.

public class HelloFragment extends Fragment {
        private static final String TAG = HelloFragment.class.getSimpleName();
        @Override
        public void onAttach(Context context) {
                super.onAttach(context);
                Log.i(TAG, "onAttach");
        }
        @Override
        public void onCreate(Bundle savedInstanceState) {
                super.onCreate(savedInstanceState);
                Log.i(TAG, "onCreate");
        }
        @Nullable
        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
                Log.i(TAG, "onCreateView");
                return inflater.inflate(R.layout.fragment_hello, container, false);
        }
        @Override
        public void onActivityCreated(Bundle savedInstanceState) {
                super.onActivityCreated(savedInstanceState);
                Log.i(TAG, "onActivityCreated");
        }
        @Override
        public void onStart() {
                super.onStart();
                Log.i(TAG, "onStart");
        }
        @Override
        public void onResume() {
                super.onResume();
                Log.i(TAG, "onResume");
        }

....

Create layout

<?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:background="#FF0"
                          android:orientation="vertical">

        <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_margin="10dp"
                android:text="Hello From Fragment"
                android:textColor="@android:color/black"/>

</LinearLayout>

Place the Fragment inside an Activity

Fragment Manager

We use a Fragment manager to manager the fragments transaction which are methods which add, remove or replace fragments for an activity.