Understand lifecycle of Activity and Fragment, Introduction

To develop Android Apps run on Fragment, understanding of lifecycle of Activity and Fragment is very important. (I'm confused now!)

It is a simple exercise to load Fragment using FragmentTransaction, with all lifecycle methods overrided to display the status on Toast and output to Log. Such that you can easy understand the lifecycle behavior between Activity and Fragment.

MainActivity.java

package com.example.androidfragmenttest;

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.FrameLayout;
import android.widget.Toast;
import android.app.Activity;

public class MainActivity extends  FragmentActivity {
 
 static public class MyFragment1 extends Fragment {
  
  String savedText;

  @Override
  public void onAttach(Activity activity) {
   toastFragment1Method();
   super.onAttach(activity);
  }

  @Override
  public void onCreate(Bundle savedInstanceState) {
   toastFragment1Method();
   super.onCreate(savedInstanceState);
  }

  @Override
  public View onCreateView(LayoutInflater inflater, ViewGroup container,
    Bundle savedInstanceState) {
   toastFragment1Method();
   View view = inflater.inflate(R.layout.fragment_layout1, null);
   return view;
  }
  
  @Override
  public void onActivityCreated(Bundle savedInstanceState) {
   toastFragment1Method();
   super.onActivityCreated(savedInstanceState);
  }

  @Override
  public void onStart() {
   toastFragment1Method();
   super.onStart();
  }

  @Override
  public void onResume() {
   toastFragment1Method();
   super.onResume();
  }

  @Override
  public void onPause() {
   toastFragment1Method();
   super.onPause();
  }

  @Override
  public void onStop() {
   toastFragment1Method();
   super.onStop();
  }

  @Override
  public void onDestroyView() {
   toastFragment1Method();
   super.onDestroyView();
  }

  @Override
  public void onDestroy() {
   toastFragment1Method();
   super.onDestroy();
  }

  @Override
  public void onDetach() {
   toastFragment1Method();
   super.onDetach();
  }
  
  private void toastFragment1Method(){
   StackTraceElement[] s = Thread.currentThread().getStackTrace();
   String methodName = s[3].getMethodName();
   Toast.makeText(getActivity(), 
     "MyFragment1 : " + methodName, Toast.LENGTH_SHORT).show();
   
   Log.i("MYTAG", "MyFragment1 : " + methodName);
  }

 }
 
 FrameLayout fragmentContainer;

 @Override
 protected void onCreate(Bundle savedInstanceState) {
  toastActivityMethod();
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  
  fragmentContainer = (FrameLayout)findViewById(R.id.container);
  if(savedInstanceState == null){
   //if's the first time created
   MyFragment1 myListFragment1 = new MyFragment1();
   FragmentManager supportFragmentManager = getSupportFragmentManager();
   FragmentTransaction fragmentTransaction = supportFragmentManager.beginTransaction();
   fragmentTransaction.add(R.id.container, myListFragment1);
   fragmentTransaction.commit(); 
  }
  
 }
 
 @Override
 protected void onStart() {
  toastActivityMethod();
  super.onStart();
 }

 @Override
 protected void onResume() {
  toastActivityMethod();
  super.onResume();
 }

 @Override
 protected void onPause() {
  toastActivityMethod();
  super.onPause();
 }
 
 @Override
 protected void onStop() {
  toastActivityMethod();
  super.onStop();
 }

 @Override
 protected void onDestroy() {
  toastActivityMethod();
  super.onDestroy();
 }

 private void toastActivityMethod(){
  StackTraceElement[] s = Thread.currentThread().getStackTrace();
  String methodName = s[3].getMethodName();
  Toast.makeText(getApplicationContext(), 
    "MainActivity : " + methodName, Toast.LENGTH_SHORT).show();
  
  Log.i("MYTAG", "MainActivity : " + methodName);
 }

}

/res/layout/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:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity" >

    <FrameLayout
        android:id="@+id/container"
        android:layout_width="match_parent"
        android:layout_height="match_parent" >
    </FrameLayout>

</RelativeLayout>

/res/layout/fragment_layout1.xml

<LinearLayout 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:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:orientation="vertical"
    tools:context=".MainActivity" >

    <TextView 
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Fragment 1"/>
    
</LinearLayout>

Download the files.

To view the Log in Eclipse, Show View of LogCat in Window menu; select info and enter tag:MYTAG in the search box.

Suggested Android Developers doc:
- Activity
- Fragments

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Next:

• Different case in lifecycle of Activity and Fragment
• UI elements lost after Activity/Fragment re-created
• How setRetainInstance(true) affect lifecycle of Fragment
• Lifecycle of dual fragment activity