Efficient Android Threading

279 Pages·2014·12.03 MB·English

by  Anders Göransson

Efficient Android Threading
Anders Göransson
Efficient Android Threading
by Anders Göransson
Copyright © 2014 Anders Göransson. All rights reserved.
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May 2014: First Edition
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2014-05-21: First release
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ISBN: 978-1-449-36413-7
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Table of Contents
Preface. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi
1. Android Components and the Need for Multiprocessing. . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Android Software Stack 1
Application Architecture 2
Application 3
Components 3
Application Execution 5
Linux Process 6
Lifecycle 6
Structuring Applications for Performance 9
Creating Responsive Applications Through Threads 9
Summary 11
Part I. Fundamentals
2. Multithreading in Java. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Thread Basics 15
Execution 15
Single-Threaded Application 17
Multithreaded Application 17
Thread Safety 19
Intrinsic Lock and Java Monitor 20
Synchronize Access to Shared Resources 22
Example: Consumer and Producer 24
Task Execution Strategies 26
Concurrent Execution Design 27
v
Summary 27
3. Threads on Android. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Android Application Threads 29
UI Thread 29
Binder Threads 30
Background Threads 30
The Linux Process and Threads 31
Scheduling 34
Summary 37
4. Thread Communication. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Pipes 39
Basic Pipe Use 40
Example: Text Processing on a Worker Thread 42
Shared Memory 44
Signaling 45
BlockingQueue 46
Android Message Passing 47
Example: Basic Message Passing 49
Classes Used in Message Passing 51
Message 55
Looper 58
Handler 60
Removing Messages from the Queue 68
Observing the Message Queue 70
Communicating with the UI Thread 73
Summary 74
5. Interprocess Communication. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
Android RPC 75
Binder 76
AIDL 77
Synchronous RPC 79
Asynchronous RPC 81
Message Passing Using the Binder 83
One-Way Communication 84
Two-Way Communication 86
Summary 87
6. Memory Management. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
Garbage Collection 89
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Thread-Related Memory Leaks 91
Thread Execution 92
Thread Communication 98
Avoiding Memory Leaks 101
Use Static Inner Classes 101
Use Weak References 101
Stop Worker Thread Execution 102
Retain Worker Threads 102
Clean Up the Message Queue 102
Summary 103
Part II. Asynchronous Techniques
7. Managing the Lifecycle of a Basic Thread. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
Basics 107
Lifecycle 107
Interruptions 108
Uncaught Exceptions 110
Thread Management 112
Definition and Start 112
Retention 114
Summary 119
8. HandlerThread: A High-Level Queueing Mechanism. . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
Fundamentals 121
Lifecycle 123
Use Cases 124
Repeated Task Execution 125
Related Tasks 125
Task Chaining 128
Conditional Task Insertion 131
Summary 131
9. Control over Thread Execution Through the Executor Framework. . . . . . . . . . . . . . . . . 133
Executor 133
Thread Pools 136
Predefined Thread Pools 136
Custom Thread Pools 137
Designing a Thread Pool 138
Lifecycle 142
Shutting Down the Thread Pool 143
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Thread Pool Uses Cases and Pitfalls 145
Task Management 146
Task Representation 146
Submitting Tasks 147
Rejecting Tasks 151
ExecutorCompletionService 152
Summary 154
10. Tying a Background Task to the UI Thread with AsyncTask. . . . . . . . . . . . . . . . . . . . . . . 157
Fundamentals 157
Creation and Start 160
Cancellation 161
States 162
Implementing the AsyncTask 163
Example: Downloading Images 164
Background Task Execution 167
Application Global Execution 169
Execution Across Platform Versions 170
Custom Execution 172
AsyncTask Alternatives 173
When an AsyncTask Is Trivially Implemented 173
Background Tasks That Need a Looper 174
Local Service 174
Using execute(Runnable) 174
Summary 175
11. Services. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177
Why Use a Service for Asynchronous Execution? 177
Local, Remote, and Global Services 179
Creation and Execution 181
Lifecycle 181
Started Service 183
Implementing onStartCommand 184
Options for Restarting 184
User-Controlled Service 186
Task-Controlled Service 190
Bound Service 192
Local Binding 194
Choosing an Asynchronous Technique 197
Summary 198
12. IntentService. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199
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