Android Tutorials - Herong's Tutorial Examples - v3.05, by Herong Yang
Implementing Activity Callback Methods
This section provides a tutorial example on how to implement activity callback methods using ActivityLog application as an example to log a short message from each callback method in a log file.
In this tutorial, I am going to enhance my ActivityLog application to implement other callback methods. See the ActivityLog.java source code below:
/* ActivityLog.java * Version 2.0 - Adding more callback methods * Copyright (c) 2015, HerongYang.com, All Rights Reserved. */ package com.herongyang.activity; import android.app.Activity; import android.os.Bundle; import android.widget.TextView; import android.content.Context; import java.io.*; public class ActivityLog extends Activity { @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); String msg = ""; msg += "Activity created\n"; msg += "----------------\n"; TextView tv = new TextView(this); tv.setText(msg); setContentView(tv); logLine("Checkpoint #1 - onCreate() called"); } public void onStart() { //working super.onStart(); logLine("Checkpoint #2 - onStart() called"); } public void onResume() { super.onResume(); logLine("Checkpoint #3 - onResume() called"); } public void onPause() { super.onPause(); logLine("Checkpoint #4 - onPause() called"); } public void onStop() { super.onStop(); logLine("Checkpoint #5 - onStop() called"); } public void onRestart() { super.onRestart(); logLine("Checkpoint #6a - onRestart() called"); } public void onDestroy() { super.onDestroy(); logLine("Checkpoint #6b - onDestroyed() called"); } public void logLine(String msg) { try { FileOutputStream fos = openFileOutput("Activity.log", Context.MODE_APPEND); OutputStreamWriter out = new OutputStreamWriter(fos); out.write((new java.util.Date()).toString()+": "+msg+"\n"); out.close(); fos.close(); } catch (Exception e) { e.printStackTrace(System.err); } } }
Some notes on the enhanced ActivityLog.java code:
Now build and install the enhanced version of ActivityLog to the emulator. Then follow next tutorials on how to test the activity lifecycle by running ActivityLog in different ways.
Table of Contents
Installing JDK 1.8 on Windows System
Installation of Android SDK R24 and Emulator
Installing Apache Ant 1.9 on Windows System
Developing First Android Application - HelloAndroid
Android Application Package (APK) Files
Android Debug Bridge (adb) Tool
AboutAndroid - Application to Retrieve System Information
►android.app.Activity Class and Activity Lifecycle
Introduction of Activity Lifecycle
onCreate() and Other Callback Methods
ActivityLog - Application to Create Log File
Viewing Activity Log File with "cat" Command in "adb shell"
►Implementing Activity Callback Methods
ActivityLog Test - Activity Terminated by User
ActivityLog Test - Activity Stopped and Restarted
ActivityLog Test - Activity Paused and Resumed
View Objects and Layout Resource Files
Using "adb logcat" Command for Debugging
Build Process and Package File Content
Samsung Galaxy Tab 3 Mini Tablet
USB Debugging Applications on Samsung Tablet
USB Debugging Applications on LG-V905R Tablet