Android 4.0开发指南：从环境配置到高级特性

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本篇文档是关于"Android 4.0"的深入指南，由Apress出版，专为Android开发者设计。书中涵盖了从入门到进阶的各种主题，旨在帮助读者全面理解和掌握Android 4.0平台。主要内容分为多个章节： 1. **第1章：介绍Android计算平台** - 引导读者理解Android的核心概念和架构，为后续开发打下基础。 2. **第2章：设置开发环境** - 指导如何配置和搭建适用于Android 4.0项目的开发工具，包括安装SDK、调试器等。 3. **第3章：理解Android资源** - 讲解Android应用程序中的各种资源管理，如布局文件、图片、字符串和样式等。 4. **第4章：理解Content Providers** - 内容提供者是Android的核心组件，用于数据共享和跨应用通信。 5. **第5章：理解Intents** - 介绍Android的消息传递机制，如何使用Intent实现应用程序间的交互。 6. **第6章：构建用户界面与控件** - 学习如何创建美观且响应式的UI元素，包括各种控件的使用和布局管理。 7. **第7章：菜单与导航** - 探讨Android菜单系统和上下文菜单的使用，提升用户体验。 8. **第8章：Fragment for tablets and more** - 针对平板电脑和大屏幕设备，讲解Fragment的使用，支持多屏应用设计。 9. **第9章：工作与对话框** - 如何设计和展示对话框，处理用户输入和反馈。 10. **第10章：探索Action Bar** - 介绍Android 4.0中的新特性，即Action Bar，对头部导航栏的优化。 11. **第11章：高级调试与分析** - 提供实用的调试技巧和性能分析方法，帮助开发者解决疑难问题。 12. **第12章：应对配置变化** - 学习如何使应用在不同设备和屏幕尺寸上保持一致性，处理不同环境下的行为调整。 13. **第13章：处理偏好设置与保存状态** - 掌握用户设置的管理和保存，提高应用的个性化和易用性。 14. **第14章：探索安全与权限** - 讨论Android的安全模型，以及如何正确地请求和管理应用程序权限。 15. **第15章：构建和服务** - 学习服务的概念，以及如何创建后台运行的服务来支持复杂功能。 16. **第16章：探索包管理** - 解析Android的包结构，理解如何组织和分发应用组件。 17. **第17章：探索Handler** - 深入理解Android消息处理机制，包括Handler和Looper的使用。这本指南详细而全面，无论是初学者还是有经验的开发者，都能从中找到所需的知识和技能，帮助他们在Android 4.0平台上高效开发高质量的应用程序。

CHAPTER 1: Introducing the Android Computing Platform

loaded as XML files and because resource IDs for those menus are auto-generated.

Here’s how you would declare menus in an XML file:

<item android:id="@+id/menu_clear"

android:orderInCategory="10"

android:title="clear" />

<item android:id="@+id/menu_show_browser"

android:orderInCategory="5"

android:title="show browser" />

</group>

</menu>

Android supports dialogs, and all dialogs in Android are asynchronous. These

asynchronous dialogs present a special challenge to developers accustomed to the

synchronous modal dialogs in some windowing frameworks. We’ll address menus in

Chapter 7 and dialogs in Chapter 9.

Android offers extensive support for animation. There are three fundamental ways to

accomplish animation. You can do frame-by-frame animation. Or you can provide

tweening animation by changing view transformation matrices (position, scale, rotation,

and alpha). Or you can also do tweening animation by changing properties of objects.

The property-based animation is introduced in 3.0 and is the most flexible and

recommended way to accomplish animation. All of these animations are covered in

Chapter 21.

Moreover, Android allows you to define these animations in an XML resource file. Check

out this example, in which a series of numbered images is played in frame-by-frame

animation:

<animation-list xmlns:android="http://schemas.android.com/apk/res/android"

android:oneshot="false">

……

</animation-list>

Android also supports 3D graphics through its implementation of the OpenGL ES 1.0

and 2.0 standards. OpenGL ES, like OpenGL, is a C-based flat API. The Android SDK,

because it’s a Java-based programming API, needs to use Java binding to access the

OpenGL ES. Java ME has already defined this binding through Java Specification

Request (JSR) 239 for OpenGL ES, and Android uses the same Java binding for

OpenGL ES in its implementation. If you are not familiar with OpenGL programming, the

learning curve is steep. Due to space limitations, we are not able to include the OpenGL

coverage in the fourth edition of the book. However we have over 100 pages of

coverage in our third edition.

Android has a number of new concepts that revolve around information at your fingertips

using the home screen. The first of these is live folders. Using live folders, you can

publish a collection of items as a folder on the homepage. The contents of this collection

change as the underlying data changes. This changing data could be either on the

CHAPTER 1: Introducing the Android Computing Platform

device or from the Internet. Due to space limitations, we are not able to cover live folders

in the fourth edition of the book. However, the third edition includes extensive coverage.

The second homepage-based idea is the home screen widget. Home screen widgets are

used to paint information on the homepage using a UI widget. This information can

change at regular intervals. An example could be the number of e-mail messages in your

e-mail store. We describe home screen widgets in Chapter 25. The home screen

widgets are enhanced in 3.0 to include list views that can get updated when their

underlying data changes. These enhancements are covered in Chapter 26.

Integrated Android Search is the third homepage-based idea. Using integrated search,

you can search for content both on the device and also across the Internet. Android

search goes beyond search and allows you to fire off commands through the search

control. Due to space limitations, we can’t include coverage of the search API in the

fourth edition of the book. However, it is covered in the third edition.

Android also supports touchscreen and gestures based on finger movements on the

device. Android allows you to record any random motion on the screen as a named

gesture. This gesture can then be used by applications to indicate specific actions. We

cover touchscreens and gestures in Chapter 27.

Sensors are now becoming a significant part of the mobile experience. We cover

sensors in Chapter 29.

Another necessary innovation required for a mobile device is the dynamic nature of its

configurations. For instance, it is very easy to change the viewing mode of a handheld

between portrait and landscape. Or you may dock your handheld to become a laptop.

Android 3.0 has introduced a concept called fragments to deal with these variations

effectively. Chapter 8 is dedicated to fragments, and Chapter 12 talks about how to deal

with configuration changes.

We also cover the 3.0 feature (which is much enhanced in 4.0) of action bars in Chapter 10.

Action bars bring Android up to par with a desktop menu bar paradigm.

Drag-and-drop is introduced for tablets in 3.0. This feature is now available to phones as

well. We cover drag-and-drop in Chapter 28.

Handheld devices are fully aware of a cloud-based environment. To make server-side

HTTP calls, it is important to understand the threading model to avoid Application Not

Responding messages. We cover the mechanisms available for asynchronous

processing in Chapter 18.

Outside of the Android SDK, there are a number of independent innovations taking place

to make development exciting and easy. Some examples are XML/VM, PhoneGap, and

Titanium. Titanium allows you to use HTML technologies to program the WebKit-based

Android browser. We covered Titanium in the second edition of this book. However, due

to time and space limitations, we are not covering Titanium in this edition.

CHAPTER 1: Introducing the Android Computing Platform

Android Service Components

Security is a fundamental part of the Android platform. In Android, security spans all

phases of the application life cycle—from design-time policy considerations to runtime

boundary checks. We cover security and permissions in Chapter 14.

In Chapter 15, we’ll show you how to build and consume services in Android,

specifically HTTP services. This chapter will also cover interprocess communication

(communication between applications on the same device).

Location-based service is another of the more exciting components of the Android SDK.

This portion of the SDK provides application developers with APIs to display and

manipulate maps, as well as obtain real-time device-location information. We’ll cover

these ideas in detail in Chapter 22.

Android Media and Telephony Components

Android has APIs that cover audio, video, and telephony components. Chapter 23 will

address the telephony API. We’ll cover the audio and video APIs extensively in

Chapter 24.

Starting with Android 2.0, Android includes the Pico Text-to-Speech engine. Due to

space limitations, we are not able to include Text-to-Speech coverage in the fourth

edition of the book. The third edition does cover the Text-to-Speech API.

Last but not least, Android ties all these concepts into an application by creating a single

XML file that defines what an application package is. This file is called the application’s

manifest file (AndroidManifest.xml). Here is an example:

<?xml version="1.0" encoding="utf-8"?>

<manifest xmlns:android="http://schemas.android.com/apk/res/android"

package="com.ai.android.HelloWorld"

android:versionCode="1"

android:versionName="1.0.0">

<activity android:name=".HelloWorld"

android:label="@string/app_name">

<intent-filter>

</intent-filter>

</activity>

</application>

</manifest>

The Android manifest file is where activities are defined, where services and content

providers are registered, and where permissions are declared. Details about the

manifest file will emerge throughout the book as we develop each idea.

CHAPTER 1: Introducing the Android Computing Platform

Android Java Packages

One way to get a quick snapshot of the Android platform is to look at the structure of

Java packages. Because Android deviates from the standard JDK distribution, it is

important to know what is supported and what is not. Here’s a brief description of the

important packages that are included in the Android SDK:

android.app: Implements the Application model for Android. Primary

classes include Application, representing the start and stop

semantics, as well as a number of activity-related classes, fragments,

controls, dialogs, alerts, and notifications. We work with most of these

classes through out this book.

android.app.admin: Provides the ability to control the device by folks

such as enterprise administrators.

android.accounts: Provides classes to manage accounts such as

Google, Facebook, and so on. The primary classes are

AccountManager and Account. We cover this API briefly in Chapter 30

when we discuss the Contacts API.

android.animation: Hosts all the new property animation classes.

These clases are extensively covered in Chapter 21.

android.app.backup: Provides hooks for applications to back up and

restore their data when folks switch their devices.

android.appwidget: Provides functionality for home screen widgets.

This package is covered extensively in Chapter 25 and Chapter 26

when we talk about home screen widgets, including list-based

widgets.

android.bluetooth: Provides a number of classes to work with

Bluetooth functionality. The main classes include BluetoothAdapter,

BluetoothDevice, BluetoothSocket, BluetoothServerSocket, and

BluetoothClass. You can use BluetoothAdapter to control the locally

installed Bluetooth adapter. For example, you can enable it, disable it,

and start the discovery process. BluetoothDevice represents the

remote Bluetooth device that you are connecting with. The two

Bluetooth sockets are used to establish communication between the

devices. A Bluetooth class represents the type of Bluetooth device you

are connecting to.

android.content: Implements the concepts of content providers.

Content providers abstract out data access from data stores. This

package also implements the central ideas around intents and Android

Uniform Resource Identifiers (URIs). These classes are covered in

Chapter 4.

CHAPTER 1: Introducing the Android Computing Platform

android.content.pm: Implements package manager–related classes. A

package manager knows about permissions, installed packages,

installed providers, installed services, installed components such as

activities, and installed applications.

android.content.res: Provides access to resource files, both

structured and unstructured. The primary classes are AssetManager

(for unstructured resources) and Resources. Some of the classes from

this package are covered in Chapter 3.

android.database: Implements the idea of an abstract database. The

primary interface is the Cursor interface. Some of the classes from this

package are covered in Chapter 4.

android.database.sqlite: Implements the concepts from the

android.database package using SQLite as the physical database.

Primary classes are SQLiteCursor, SQLiteDatabase, SQLiteQuery,

SQLiteQueryBuilder, and SQLiteStatement. However, most of your

interaction is going to be with classes from the abstract

android.database package.

android.drm: Classes related to Digital Rights Management.

android.gesture: Houses all the classes and interfaces necessary to

work with user-defined gestures. Primary classes are Gesture,

GestureLibrary, GestureOverlayView, GestureStore, GestureStroke,

and GesturePoint. A Gesture is a collection of GestureStrokes and

GesturePoints. Gestures are collected in a GestureLibrary. Gesture

libraries are stored in a GestureStore. Gestures are named so that they

can be identified as actions. Some of the classes from this package

are covered in Chapter 27.

android.graphics: Contains the classes Bitmap, Canvas, Camera, Color,

Matrix, Movie, Paint, Path, Rasterizer, Shader, SweepGradient, and

TypeFace.

android.graphics.drawable: Implements drawing protocols and

background images, and allows animation of drawable objects.

android.graphics.drawable.shapes: Implements shapes including

ArcShape, OvalShape, PathShape, RectShape, and RoundRectShape.

android.hardware: Implements the physical Camera-related classes.

The Camera represents the hardware camera, whereas

android.graphics.Camera represents a graphical concept that’s not

to a physical camera at all.

android.hardware.usb: Lets you talk to USB devices from Android.

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Android 4.0开发指南：从环境配置到高级特性

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