1) Fragment Life Cycle – Dr James Froggatt

To make a fragment we have to:

1) Extend the fragment class
2) Give the appearance in XML or Java
3) Override the onCreateView() method to link appearance
4) Use the fragment in XML or Java

CREATING a fragment

1) Activity onCreate() called, where activity can set its view using the setContentView() method.
2) Fragment has it’s onAttach() method called after the fragment is associated with its activity. It gets a reference to the activity object which can be used as context.
3) onAttachFragment() is called by activity to notify the activity that a fragment was attached recently.
4) onCreate() is called inside the fragment

What is the difference between onCreate() in the activity, and onCreate() in the fragment?

In activity onCreate(), you use setContentView() and link the appearance, in onCreate() of the fragment you are not supposed to access UI elements of the fragment because the activity onCreate() may not yet be finished,however, you can create background threads here for longer running operations

5) onCreateView() method called in the fragment – this is where you link the layout file of the fragment to its object
6) onActivityCreated() is called AFTER the activities onCreate() method is completed. So here you can access UI elements through this method.
7) onStart() is called in the activity
8) onStart() is called in the fragment
9) onResume() is called in the activity
10) onResume() is called in the fragment

In the blue box, this represents the methods that are called for each fragment. For every fragment 3,4,5 are called and finally 6.

when a fragment is about to be destroyed

onSaveInstanceState() is used to save information about the fragment/activity in the Bundle object
onDestroyView() is called after the fragment view hierarchy is no longer accessible
onDestroy() is called after the fragment is not used, it still exists as a java object attached to the activity
onDetach() – fragment is not tied to the activity, and does not have a view hierarchy

Demo of fragment lifecycle with code

MainActivity.java

package com.jamesfroggatt.fragments1.app;

import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.view.Menu;


public class MainActivity extends ActionBarActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }


}

MyFragment.java

package com.jamesfroggatt.fragments1.app;

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


public class MyFragment extends Fragment{


    @Override
    public void onAttach(Activity activity) {
        Log.i("Fragment ","onAttach");
        super.onAttach(activity);
    }


    @Override
    public void onCreate(Bundle savedInstanceState) {
        Log.i("Fragment ","onCreate");
        super.onCreate(savedInstanceState);
    }


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        Log.i("Fragment ","onCreateView");
       // return super.onCreateView(R.layout.james_fragment_layout, container, false);
        return inflater.inflate(R.layout.james_fragment_layout, container, false);
    }


    @Override
    public void onActivityCreated(Bundle savedInstanceState) {
        Log.i("Fragment ","onActivityCreated");
        super.onActivityCreated(savedInstanceState);

    }


    @Override
    public void onStart() {
        Log.i("Fragment ","onStart");
        super.onStart();
    }


    @Override
    public void onResume() {
        Log.i("Fragment ","onResume");
        super.onResume();

    }

    @Override
    public void onPause() {
        Log.i("Fragment ","onPause");
        super.onPause();
    }

    @Override
    public void onSaveInstanceState(Bundle outState) {
        Log.i("Fragment ","onSaveInstanceState");
        super.onSaveInstanceState(outState);
    }

    @Override
    public void onStop() {
        Log.i("Fragment ","onStop");
        super.onStop();
    }


    @Override
    public void onDestroyView() {
        Log.i("Fragment ","onDestroyView");
        super.onDestroyView();
    }


    @Override
    public void onDestroy() {
        Log.i("Fragment ","onDestroy");
        super.onDestroy();
    }


    @Override
    public void onDetach() {
        Log.i("Fragment ","onDetach");
        super.onDetach();
    }
}

activity_main.xml

<RelativeLayout 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:background="#ffcc0044"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingBottom="@dimen/activity_vertical_margin"
    tools:context="com.jamesfroggatt.fragments1.app.MainActivity">

    <TextView
        android:text="@string/hello_world"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

    <fragment
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:name="com.jamesfroggatt.fragments1.app.MyFragment"
        tools:layout="@layout/james_fragment_layout" />

</RelativeLayout>

james_fragment_layout.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"
    android:paddingLeft="100dp"
    android:background="#ffccc320"
    >

    <TextView
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:background="#ff30cc4e"
        android:paddingLeft="50dp"
        android:text="This is MyFragment"/>

</LinearLayout>

Demo of fragment lifecycle and activity lifecycle with code

MainActivity.java

package com.jamesfroggatt.fragments1.app;

import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.util.Log;
import android.view.Menu;


public class MainActivity extends ActionBarActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Log.e("Activity ","onCreate");
        setContentView(R.layout.activity_main);
    }

    @Override
    protected void onStop() {
        super.onStop();
        Log.e("Activity ","onStop");
    }

    @Override
    protected void onRestoreInstanceState(Bundle savedInstanceState) {
        super.onRestoreInstanceState(savedInstanceState);
        Log.e("Activity ","onRestoreInstanceState");
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        Log.e("Activity ","onDestroy");
    }

    @Override
    protected void onPause() {
        super.onPause();
        Log.e("Activity ","onPause");
    }

    @Override
    protected void onResume() {
        super.onResume();
        Log.e("Activity ","onResume");
    }

    @Override
    protected void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);
        Log.e("Activity ","onSaveInstanceState");
    }

    @Override
    protected void onStart() {
        super.onStart();
        Log.e("Activity ","onStart");
    }

    @Override
    protected void onRestart() {
        super.onRestart();
        Log.e("Activity ","onRestart");
    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {

        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }


}

MyFragment.java

package com.jamesfroggatt.fragments1.app;

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


public class MyFragment extends Fragment{


    @Override
    public void onAttach(Activity activity) {
        Log.i("Fragment ","onAttach");
        super.onAttach(activity);
    }


    @Override
    public void onCreate(Bundle savedInstanceState) {
        Log.i("Fragment ","onCreate");
        super.onCreate(savedInstanceState);
    }


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        Log.i("Fragment ","onCreateView");
        // return super.onCreateView(R.layout.james_fragment_layout, container, false);
        return inflater.inflate(R.layout.james_fragment_layout, container, false);
    }


    @Override
    public void onActivityCreated(Bundle savedInstanceState) {
        Log.i("Fragment ","onActivityCreated");
        super.onActivityCreated(savedInstanceState);

    }


    @Override
    public void onStart() {
        Log.i("Fragment ","onStart");
        super.onStart();
    }


    @Override
    public void onResume() {
        Log.i("Fragment ","onResume");
        super.onResume();

    }

    @Override
    public void onPause() {
        Log.i("Fragment ","onPause");
        super.onPause();
    }

    @Override
    public void onSaveInstanceState(Bundle outState) {
        Log.i("Fragment ","onSaveInstanceState");
        super.onSaveInstanceState(outState);
    }

    @Override
    public void onStop() {
        Log.i("Fragment ","onStop");
        super.onStop();
    }


    @Override
    public void onDestroyView() {
        Log.i("Fragment ","onDestroyView");
        super.onDestroyView();
    }


    @Override
    public void onDestroy() {
        Log.i("Fragment ","onDestroy");
        super.onDestroy();
    }


    @Override
    public void onDetach() {
        Log.i("Fragment ","onDetach");
        super.onDetach();
    }
}

activity_main.xml

<RelativeLayout 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:background="#ffcc0044"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingBottom="@dimen/activity_vertical_margin"
    tools:context="com.jamesfroggatt.fragments1.app.MainActivity">

    <TextView
        android:text="@string/hello_world"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

    <fragment
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:name="com.jamesfroggatt.fragments1.app.MyFragment"
        tools:layout="@layout/james_fragment_layout" />

</RelativeLayout>

james_fragment_layout.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"
    android:paddingLeft="100dp"
    android:background="#ffccc320"
    >

    <TextView
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:background="#ff30cc4e"
        android:paddingLeft="50dp"
        android:text="This is MyFragment"/>

</LinearLayout>

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