Android 依赖注入框架RoboGuice
概述
在开发应用时一个基本原则是模块化，并且尽最大可能性地降低模块之间的耦合性。Dependency injection 大大降低了类之间的依赖性，可以通过annotation描述类之间的依赖性，避免了直接调用类似的构造函数或是使用Factory来参加所需的类，从而降低类或模块之间的耦合性，以提高代码重用并增强代码的可维护性。
Google Guice提供了Java平台上一个轻量级的 Dependency injection 框架，并可以支持开发Android应用。本指南将使用Android平台来说明Google Guice的用法。(其他类似框架有Dagger,Buffernife)
RoboGuice 为Android平台上基于Google Guice开发的一个库，可以大大简化Android应用开发的代码和一些繁琐重复的代码。比如代码中可能需要大量使用findViewById在XML中查找一个View，并将其强制转换到所需类型，onCreate 中可能有大量的类似代码。RoboGuice 允许使用annotation 的方式来描述id于View之间的关系，其余的工作由roboGuice库来完成。
RoboGuice主要功能：
- 控件注入：用@InjectViews方法初始化控件，例如：@InjectView（R.id.textview1）TextView textView1。
- 资源注入：用@InjectResources方法初始化资源，例如：@InjectResource（R.string.app_name）String name。
- 系统服务注入：用@Inject方法初始化并获取系统服务，例如：@Inject LayoutInflater inflater。
- POJO对象注入：用@Inject方法注入并初始化POJO对象，例如：@Inject Foo foo。
以下示例对比看看RoboGuice的作用：
不使用RoboGuice:
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
name = (TextView) findViewById(R.id.name);
thumbnail = (ImageView) findViewById(R.id.thumbnail);
loc = (LocationManager) getSystemService(Activity.LOCATION_SERVICE);
icon = getResources().getDrawable(R.drawable.icon);
myName = getString(R.string.app_name);
name.setText( "Hello, " + myName );
}
} 使用RoboGuice:
@ContentView(R.layout.main)
class RoboWay extends RoboActivity {
@InjectView(R.id.name) TextView name;
@InjectView(R.id.thumbnail) ImageView thumbnail;
@InjectResource(R.drawable.icon) Drawable icon;
@InjectResource(R.string.app_name) String myName;
@Inject LocationManager loc;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
name.setText( "Hello, " + myName );
}
}
使用前准备工作
RoboGuice官方Demo: https://github.com/roboguice/roboguice/tree/master/astroboy
安装
方式一：添加依赖库：（不推荐，在androidStudio上报错，很诡异。不知道为什么）
- RoboGuice 3.0
- RoboBlender 3.0
- jsr330 javax.inject (JSR-330 support)
- jsr305 (optional support for @Nullable annotation, if desired)
方式二：在build.gradle中的dependecies片段中添加：(推荐)
dependencies {
provided 'org.roboguice:roboblender:3.0'
compile 'org.roboguice:roboguice:3.0'
}
参考https://github.com/roboguice/roboguice/wiki/InstallationNonMaven
继承类：
activities, services, and fragments都需要继承自RoboGuice提供的下列类：
- RoboActivity
- RoboListActivity
- RoboExpandableListActivity
- RoboMapActivity
- RoboPreferenceActivity
- RoboAccountAuthenticatorActivity
- RoboActivityGroup
- RoboTabActivity
- RoboFragmentActivity
- RoboLauncherActivity
- RoboService
- RoboIntentService
- RoboFragment
- RoboListFragment
- RoboDialogFragment
- etc.
Injection
- Inherit from RoboActivity
- Set your content view
- Annotate your views with @InjectView
public class MyActivity extends RoboActivity {
@InjectView(R.id.text1) TextView textView;
@Override
protected void onCreate( Bundle savedState ) {
setContentView(R.layout.myactivity_layout);
textView.setText("Hello!");
}
}@ContentView注解：
@ContentView(R.layout.myactivity_layout)
public class MyActivity extends RoboActivity {
@InjectView(R.id.text1) TextView textView;
@Override
protected void onCreate( Bundle savedState ) {
textView.setText("Hello!");
}
}
将View注入Fragment@InjectView
由于Fragment中的依赖注入发生在onViewCreated()中，所以需要在onViewCreated中调用super.onViewCreate()之后才能使用注入的View.
注意这里的：onViewCreated是在onCreateView调用之后恢复保存的状态到View之前立马调用，
@InjectView TextView commentEditText;
@Override
public void onViewCreated(View view, Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
commentEditText.setText("Some comment");
}
注入Resource到Activity:@InjectResource
public class MyActivity extends RoboActivity {
@InjectResource(R.anim.my_animation) Animation myAnimation;
}
注入System Service:@Inject
class MyActivity extends RoboActivity {
@Inject Vibrator vibrator;
@Inject NotificationManager notificationManager;
注入POJO:@Inject
注意：需要提供一个无参数构造器
class MyActivity extends RoboActivity {
@Inject Foo foo; // this will basically call new Foo();
}当然如果不想使用默认构造器，可以注解构造器：
class Foo {
Bar bar;
@Inject
public Foo(Bar bar) {
this.bar = bar;
}
}也可以注解POJO的Field:
class Foo {
@Inject Bar bar;
// Roboguice doesn't need a constructor, but you might...
}
注入Singleton
前提：对单例类使用@Singleton@Singleton //a single instance of Foo is now used though the whole app
class Foo {
}
class MyActivity extends RoboActivity {
@Inject Foo foo; // this will basically call new Foo();
}
注意：这个单例一旦创建会一直驻留内存，其他类似的还有@ContextSingleton,@FragmentSingletion，他们的作用范围比较小，利于垃圾回收。
自定义Binding
public interface IFoo {}
public class Foo implements IFoo {}
public class MyActivity extends RoboActivity {
//How to tell RoboGuice to inject an instance of Foo ?
@Inject IFoo foo;
}
步骤：
1.向AndroidManifest.xml中添加meta-data
<application ...>
<meta-data android:name="roboguice.modules"
android:value="com.example.MyModule,com.example.MyModule2" />
</application>
2.继承AbstractModule
public class MyModule extends AbstractModule {
//a default constructor is fine for a Module
public void bind() {
bind(IFoo.class).to(Foo.class);
}
}
public class MyModule2 extends AbstractModule {
//if your module requires a context, add a constructor that will be passed a context.
private Context context;
//with RoboGuice 3.0, the constructor for AbstractModule will use an `Application`, not a `Context`
public MyModule( Context context ) {
this.context = context;
}
public void bind() {
bind(IFoo.class).toInstance( new Foo(context));
}
}
注入到Service与BroadcastReceiver:
public class MyService extends RoboService {
@Inject ComputeFooModule computeFooModule;
public class MyBroadcastReceiver extends RoboBroadcastReceiver {
@Inject ComputeFooModule computeFooModule;
注入到自定义View
class MyView extends View {
@Inject Foo foo;
@InjectView(R.id.my_view) TextView myView;
public MyView(Context context) {
inflate(context,R.layout.my_layout, this);
RoboGuice.getInjector(getContext()).injectMembers(this);//注意这一行，为了使其正常工作。
}
public MyView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
inflate(context,R.layout.my_layout, this);
RoboGuice.getInjector(getContext()).injectMembers(this);
}
public MyView(Context context, AttributeSet attrs) {
super(context, attrs);
inflate(context,R.layout.my_layout, this);
RoboGuice.getInjector(getContext()).injectMembers(this);
}
@Override
public void onFinishInflate() {
super.onFinishInflate();
//All injections are available from here
//in both cases of XML and programmatic creations (see below)
myView.setText(foo.computeFoo());
}
}
使用RoboGuice Event
public class MyActivity extends RoboActivity {
// Any method with void return type and a single parameter with @Observes annotation
// can be used as an event listener. This one listens to onResume.
public void doSomethingOnResume( @Observes OnResumeEvent onResume ) {
Ln.d("Called doSomethingOnResume in onResume");
}
// As you might expect, some events can have parameters. The OnCreate event
// has the savedInstanceState parameter that Android passes to onCreate(Bundle)
public void doSomethingElseOnCreate( @Observes OnCreateEvent onCreate ) {
Ln.d("onCreate savedInstanceState is %s", onCreate.getSavedInstanceState())
}
// And of course, you can have multiple listeners for a given event.
// Note that ordering of listener execution is indeterminate!
public void xxx( @Observes OnCreateEvent onCreate ) {
Ln.d("Hello, world!")
}
}
本文还有很多特性没有介绍到，后续可能会进行补充。
参考：
http://www.oschina.net/p/roboguice
https://github.com/roboguice/roboguice/wiki
http://mobile.51cto.com/abased-426620.htm