Android App-Hook and Plug-In Technology

This book presents the Android plug-in technology used in Android development. This technology is widely used by a majority of Chinese internet companies, and is becoming more widely used worldwide. The book fully describes the history of Android plug-in technology, the installation and startup process, and new features of the Android plug-in technology. It also explores plug-in solutions for peripheral technologies. The book is designed to help Android app developers better understand the underlying technology of the Android system. Features Introduces Android system knowledge, including the communication between AMS and four components Describes the Hook technique by Proxy.newProxyInstance and reflection, to modify Android system behavior, for example, to launch an activity not declared in the AndroidManifest. Shows how to use the Hook apk packaging process in Gradle Covers how to merge the resources in the plugin app and the host app, and how to merge dex of the host app and all the plugin apps Presents the SO technique and how to launch SO files dynamically

Contents Acknowledgments, xvii About the Author, xix About the Translators, xxi Introduction, xxiii Chapter 1 ? Plug-Ins from the Past to the Future 1 1.1 ANDROID PLUG-INS IN CHINA 1 1.2 HISTORY OF ANDROID PLUG-IN TECHNIQUES 2 1.3 USAGE OF PLUG-INS 8 1.4 ANOTHER CHOICE: REACT NATIVE 9 1.5 DO ALL COMPONENTS REQUIRE PLUG-INS? 10 1.6 DOUBLE-OPENING AND VIRTUAL MACHINE 10 1.7 FROM NATIVE TO HTML5 11 1.8 SUMMARY 12 Chapter 2 ? The Underlying Knowledge of Android 13 2.1 OVERVIEW OF UNDERLYING ANDROID KNOWLEDGE 13 2.2 BINDER 15 2.3 AIDL 17 2.4 ACTIVITYMANAGERSERVICE 22 2.5 ACTIVITY WORKING PRINCIPLES 23 2.5.1 How to Launch an App 23 2.5.2 Starting the App Is Not So Simple 24 2.5.2.1 Click the App Icon in Launcher and Send a Message to the AMS 25 2.5.2.2 The AMS Handles the Information from the Launcher 30 2.5.2.3 The Launcher Goes to Sleep and Informs the AMS Again 31 2.5.2.4 The AMS Creates a New Process 33 2.5.2.5 Start a New Process and Inform the AMS 34 2.5.2.6 The AMS Tells the New App Which Activity to Launch 35 2.5.2.7 The Amazon App Starts an Activity 35 2.6 NAVIGATION IN APP 37 2.7 FAMILY OF CONTEXT 38 2.8 SERVICE 41 2.8.1 Start Service in a New Process 41 2.8.1.1 The App Sends a Message to the AMS to Launch Service 42 2.8.1.2 The AMS Creates a New Process 42 2.8.1.3 Start a New Process and Inform the AMS 43 2.8.1.4 The AMS Sends Information to the New Process 43 2.8.1.5 New Process to Launch Service 43 2.8.2 Start a Service in the Same Process 44 2.8.3 Bind a Service in the Same Process 44 2.8.3.1 The App Sends a Message to the AMS to Bind a Service 45 2.8.3.2 The AMS Sends Two Messages to the App Process 45 2.8.3.3 The App Receives the First Message 45 2.8.3.4 The App Receives the Second Message and Sends a Binder Object to the AMS 46 2.8.3.5 AMS Informs the App 46 2.9 BROADCASTRECEIVER 47 2.9.1 Registration 48 2.9.2 Send a Broadcast 49 2.10 CONTENTPROVIDER 51 2.10.1 The Essence of the ContentProvider 54 2.10.2 The ASM 54 2.10.3 Communication between ContentProvider and the AMS 56 2.11 THE PMS AND APP INSTALLATION PROCESS 57 2.11.1 PMS Introduction 57 2.11.2 App Installation Process 58 2.11.3 PackageParser 59 2.11.4 ActivityThread and PackageManager 60 2.12 CLASSLOADER 61 2.13 PARENT-DELEGATION 63 2.14 MULTIDEX 63 2.15 A MUSIC PLAYER APP 65 2.15.1 A Music Player Based on Two Receivers 65 2.15.2 A Music Player Based on One Receiver 71 2.16 SUMMARY 77 Chapter 3 ? Reflection 79 3.1 BASIC REFLECTION 79 3.1.1 Get the Class Using a String 80 3.1.1.1 Get the Class Using a String 80 3.1.1.2 Class.forName 80 3.1.1.3 Property class 80 3.1.1.4 Property TYPE 80 3.1.2 Get the Property and Method of the Class 81 3.1.2.1 Get the Constructor of the Class 81 3.1.2.2 Invoke a Private Method of the Class 83 3.1.2.3 Invoke a Private and Static Method of the Class 84 3.1.2.4 Get a Private Field of the Class and Modify Its Value 84 3.1.2.5 Get the Private Static Field of the Class and Modify Its Value 85 3.1.3 Generics and Singleton 86 3.2 jOOR 88 3.2.1 Get a Class from a String 89 3.2.1.1 Get a Class from a String 89 3.2.1.2 Get a Class by Using on and get 89 3.2.2 Get the Property and Method of a Class 90 3.2.2.1 Get a Constructor of a Class 90 3.2.2.2 Get the Private Method of the Class 90 3.2.2.3 Get the Private and Static Method of the Class 91 3.2.2.4 Get the Private Field of the Class 91 3.2.2.5 Get the Private and Static Field of the Class 91 3.2.3 Generics and Singleton 91 3.3 ENCAPSULATED CLASSES OF THE BASIC REFLECTION 93 3.3.1 Get a Constructor 93 3.3.2 Invoke Instance Methods 94 3.3.3 Invoke Static Methods 95 3.3.4 Get the Field of the Class and Set Its Value 95 3.3.5 Handle Generics 96 3.4 FURTHER ENCAPSULATION OF THE REFLECTION 97 3.4.1 Reflect a Method with Only One Parameter or without Parameters 97 3.4.2 Replace String with Class Type 100 3.4.3 Differences between the Static and Instance Fields 101 3.4.4 Optimization of the Field Reflection 102 3.5 SUMMARY 103 Chapter 4 ? Proxy Pattern 105 4.1 WHAT IS A PROXY PATTERN? 105 4.1.1 Remote Proxy 106 4.1.2 Write Log 108 4.2 STATIC-PROXY AND DYNAMIC-PROXY 109 4.3 A HOOK ON THE AMN 111 4.4 A HOOK ON THE PMS 113 4.5 SUMMARY 114 Chapter 5 ? Hooking startActivity() 115 5.1 INVOKE STARTACTIVITY() IN TWO WAYS 115 5.2 HOOKING STARTACTIVITY() OF THE ACTIVITY 116 5.2.1 Solution 1: Hooking the Method startActivityForResult of Activity 118 5.2.2 Solution 2: Hooking the Field mInstrumentation of Activity 118 5.2.3 Solution 3: Hooking the Method getDefault() of AMN 121 5.2.4 Solution 4: Hooking the Field mCallback of H 125 5.2.5 Solution 5: Hooking Instrumentation Again 128 5.3 HOOKING THE METHOD STARTACTIVITY OF CONTEXT 131 5.3.1 Solution 6: Hooking the Field mInstrumentation of ActivityThread 131 5.3.2 Which Solution Is the Best? 133 5.4 LAUNCH AN ACTIVITY NOT DECLARED IN ANDROIDMANIFEST.XML 133 5.4.1 How to Hook AMN 133 5.4.2 First Half of the Hook 135 5.4.3 Second Half of the Hook: Hooking the Field mCallback of H 139 5.4.4 Second Half of the Hook: Hooking the mInstrumentation Field of ActivityThread 141 5.5 SUMMARY 143 Chapter 6 ? The Basic Concepts of Plug-In Techniques 145 6.1 LOADING EXTERNAL DEX 145 6.2 INTERFACE-ORIENTED PROGRAMMING 148 6.3 PLUG-IN THINNING 151 6.4 DEBUGGING IN PLUG-INS 154 6.5 APPLICATION PLUG-IN SOLUTIONS 156 6.6 SUMMARY 158 Chapter 7 ? Resources in Plug-In 159 7.1 HOW TO LOAD RESOURCES IN ANDROID 159 7.1.1 Types of Resources 159 7.1.2 Resources and AssetManager 160 7.2 PLUG-IN SOLUTIONS OF RESOURCES 161 7.3 SOLUTIONS FOR CHANGING SKINS 166 7.4 ANOTHER PLUG-IN SOLUTION FOR CHANGING SKINS 178 7.5 SUMMARY 179 Chapter 8 ? The Plug-In Solution of Four Components 181 8.1 THE SIMPLEST PLUG-IN SOLUTION 181 8.1.1 Pre-Declare Activity and Service of the Plug-In in the HostApp’s AndroidManifest.xml 182 8.1.2 Combine the Dex 183 8.1.3 Start a Service of the Plug-In 184 8.1.4 Resources in Activity 185 8.2 A PLUG-IN SOLUTION FOR ACTIVITY 188 8.2.1 Launch an Activity of a Plug-In Not Declared in the AndroidManifest.xml of the HostApp 188 8.2.2 Solution 1: Based on Dynamic-Proxy 193 8.2.2.1 The Process of Launching an Activity 193 8.2.2.2 Add a Plug-In Activity to the Cache 196 8.2.2.3 Solution 1 of Loading Class in a Plug-In: Create DexClassLoader for Each Plug-In apk 201 8.2.2.4 Hooking More Classes 202 8.2.3 Solution 2: Merge All the Plug-In Dexes into One Array 205 8.2.4 Plug-In Solution of Resources 208 8.2.5 Support LaunchMode in Plug-In 208 8.2.6 Solution 3: Hook ClassLoader 212 8.3 THE PLUG-IN SOLUTION FOR SERVICE 216 8.3.1 The Relationship Between Service and Activity 216 8.3.2 StubService 218 8.3.3 Plug-In Solution to startService() 220 8.3.4 Plug-In Solution of bindService 226 8.4 A PLUG-IN SOLUTION FOR BROADCASTRECEIVER 229 8.4.1 Receiver Overview 229 8.4.2 A Plug-In Solution for Dynamic Receiver 231 8.4.3 A Plug-In Solution for Static Receiver 231 8.4.4 A Final Plug-In Solution for Static Receiver 233 8.5 A PLUG-IN SOLUTION FOR CONTENTPROVIDER 239 8.5.1 The Basic Concept of ContentProvider 239 8.5.2 A Simple Example of ContentProvider 239 8.5.3 A Plug-In Solution for ContentProvider 242 8.5.4 The Right Time to Install a ContentProvider Plug-In 245 8.5.5 The Forwarding Mechanism of ContentProvider 246 8.6 SUMMARY 247 Chapter 9 ? A Plug-In Solution Based on Static-Proxy 249 9.1 A PLUG-IN SOLUTION FOR ACTIVITY BASED ON STATIC-PROXY 249 9.1.1 The Idea of Static-Proxy 249 9.1.2 The Simplest Example of Static-Proxy 250 9.1.2.1 Jump from the HostApp to the Plug-In 251 9.1.2.2 Communication between ProxyActivity and Plug-In Activity 252 9.1.2.3 The Logic of Activity in the Plug-In 255 9.1.3 Jump in the Plug-In 255 9.1.4 Eliminate the Keyword “that” 256 9.1.5 Jump Out 259 9.1.5.1 Preparation for Jumping Out 259 9.1.5.2 Jump to Another Plug-In 260 9.1.5.3 Jump to the HostApp 260 9.1.6 Use Interface-Oriented Programming in Static-Proxy 261 9.1.7 Support for LaunchMode 267 9.1.7.1 Overview of LaunchMode 267 9.1.7.2 Plug-In Solutions for LaunchMode 269 9.2 THE PLUG-IN SOLUTION FOR SERVI

Jianqiang Bao is a senior Android app developer. For more than 15 years he has developed enterprise solutions using Silverlight, ASP.NET, WP7, Android and iOS. He has worked in HP, Microsoft, Qunar, Tuniu company. He has a technique blog http://www.cnblogs.com/jax, his GitHub is https://github.com/BaoBaoJianqiang.