Dagger2 基础入门与使用
Dagger2 依赖注入(Dependency injection ),通过注解的形式引入实体类,然后再接口Component作为桥梁沟通Moudle构建工厂模式注入到Activity/Fragment中减少我们new 实体化繁琐操作和统一管理我们的实列化对象
Dagger2官网地址
Gradle 引入 Dagger2
主目录gradle.build
dependencies { classpath 'com.neenbedankt.gradle.plugins:android-apt:1.8' }
项目gradle.build
dependencies { compile 'com.google.dagger:dagger:2.11' annotationProcessor 'com.google.dagger:dagger-compiler:2.11' }
Dagger2注入流程图过程
注意:Component查找优先级Moudle高于Inject
Dagger2 基本使用 @Inject @Moudle @Provides @Component
通过@Inject User 对象,注入一次即可,多个构造函数无须多次注入
package com.lhw.daggerdemo.bean;import javax.inject.Inject;public class User { private DataInfo mDataInfo; public String name; public int age; public String tag; @Inject public User() { } public User(DataInfo data, String tagName) { tag = tagName; mDataInfo = data; } public User(String tagName) { tag = tagName; } public User(DataInfo dataInof) { mDataInfo = dataInof; }}
新建Moudle实体类添加注解@Moudle,添加User实例化方法,给方法添加@Providers注解,提供对外@Component查找
import dagger.Module;import dagger.Provides;@Modulepublic class UserModule { @Provides User providerUser(){ return new User(); } }
新建接口MianComponent 添加@Component注解,添加 UserModule 到moudles中,然后新增一个inject 方法注入到Activity/Fragment中
注意:这里可以添加多个moudle,也可以通过dependencies依赖其他Component
@Component(modules ={UserModule.class})public interface MianComponent { void inject(MainActivity activity);}
然后我们点击Build,rebuild project构建项目工程,就会在我们的App build输出目录下面generated/ap_generated_sources/debug/out/packageName/下面出现我们的构建的工厂实体实体类
public final class DaggerMianComponent implements MianComponent { ... private Provider providerUserProvider; private MembersInjector mainActivityMembersInjector; private DaggerMianComponent(Builder builder) { assert builder != null; initialize(builder); } public static Builder builder() { return new Builder(); } public static MianComponent create() { return new Builder().build(); } @Override public void inject(MainActivity activity) { mainActivityMembersInjector.injectMembers(activity); } ...}
最后一步我们把构建好的实体类,注入到Activity/Fragment中
import javax.inject.Inject;import com.lhw.daggerdemo.component.DaggerMianComponent;public class MainActivity extends AppCompatActivity { private final static String TAG="Dagger"; @Inject User userY;//使用Inject 注解获取实例化对象User @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); //依赖绑定 DaggerMianComponent.create().inject(this); userY.name="塞班"; userY.age=18; Log.d(TAG,"userY="+userY+",tag="+userY.tag); }}//D/Dagger: userY=User{ name='塞班', age=18}
注意如果 User 里没有添加@Inject注解,只要在Moudle中添加了@Provides提供的User 对象,在inject 注入的Activity/Fragment 一样可以调用
注解@Singleton单列的使用
注意:
如果moudle 所依赖的Component中有被单例的对象,那么Component必须是单例的
@Modulepublic class UserModule { @Provides @Singleton User providerUser(){ return new User(); } @Singleton @Component(modules ={UserModule.class})public interface MianComponent { void inject(MainActivity activity);}
注解@Singleton与@Scope的区别
都是限定区域的单例形式,实现同生共死,只是@Singleton是全局型的,而@Scope是局部范围的,@Scope注解在@Provides方法时,对使用@Provides提供的依赖生效;@Scope注解在类时,对使用@Inject注解的构造方法提供的依赖生效。
@Scope作用是控制所提供依赖的生命周期,使其与容器的生命周期相同,从而实现局部单例或全局单例
Singleton.java@Scope@Documented@Retention(RUNTIME)public @interface Singleton {}Scope.java@Target(ANNOTATION_TYPE)@Retention(RUNTIME)@Documentedpublic @interface Scope {}MianComponent.java@ActivityScope //添加注解实现局部单例@Component(modules ={UserModule.class})public interface MianComponent { User getuser(); void inject(MainActivity activity); }
注意 自定义的@Singleton、@ActivityScope注解根本就没有这些功能,它的作用仅仅是“标记”,没有生成任何文件,只是多了一个DoubleCheck来进行单例的生成!
DaggerMianComponent.java private void initialize(final Builder builder) { this.providerUserProvider = DoubleCheck.provider(UserModule_ProviderUserFactory.create(builder.userModule)); this.providerUserProvider2 = DoubleCheck.provider(DataInfoModule_ProviderUserFactory.create(builder.dataInfoModule)); }
DoubleCheck.java 生成对应的单例的对象
public final class DoubleCheck implements Provider, Lazy { private static final Object UNINITIALIZED = new Object(); private volatile Provider provider; private volatile Object instance = UNINITIALIZED; private DoubleCheck(Provider provider) { assert provider != null; this.provider = provider; } @SuppressWarnings("unchecked") // cast only happens when result comes from the provider @Override public T get() { Object result = instance; if (result == UNINITIALIZED) { synchronized (this) { result = instance; if (result == UNINITIALIZED) { result = provider.get(); Object currentInstance = instance; if (currentInstance != UNINITIALIZED && currentInstance != result) { throw new IllegalStateException("Scoped provider was invoked recursively returning " + "different results: " + currentInstance + " & " + result + ". This is likely " + "due to a circular dependency."); } instance = result; provider = null; } } } return (T) result; } /** Returns a {@link Provider} that caches the value from the given delegate provider. */ public static Provider provider(Provider delegate) { checkNotNull(delegate); if (delegate instanceof DoubleCheck) { return delegate; } return new DoubleCheck(delegate); } /** Returns a {@link Lazy} that caches the value from the given provider. */ public static Lazy lazy(Provider provider) { if (provider instanceof Lazy) { @SuppressWarnings("unchecked") final Lazy lazy = (Lazy) provider; return lazy; } return new DoubleCheck(checkNotNull(provider)); }}
如果上面单例 @Singleton没有保持一致就会报错,错误由于下个节点
DataInfoModule 中使用了@Singleton而 UserModule和MianComponent没有使用时报出的错误
.MianComponent (unscoped) may not reference scoped bindings:@Component(modules ={UserModule.class})^ @Provides @Singleton com.lhw.daggerdemo.bean.DataInfo com.lhw.daggerdemo.module.DataInfoModule.providerUser()
注解@Module中的includes和@Component中的modules的使用
User.java 添加多个构造函数,添加 DataInfo对象
public class User { private DataInfo mDataInfo; public String name; public int age; public String tag; @Inject public User() { } public User(DataInfo data, String tagName) { tag = tagName; mDataInfo = data; } public User(String tagName) { tag = tagName; } public User(DataInfo dataInof) { mDataInfo = dataInof; }
DataInfo.java
public class DataInfo { @Inject public DataInfo(){} public String sex; public int height; @Override public String toString() { return "DataInfo{" + "sex='" + sex + '\'' + ", height=" + height + '}'; }}
DataInfoModule.java
@Modulepublic class DataInfoModule { @Provides @Singleton DataInfo providerUser(){ return new DataInfo(); }}
像上面那种情况我们可以有两种处理方式
- 通过includes 引入到UserMoudle中
@Module(includes = {DataInfoModule.class}) //includes 引入moudlepublic class UserModule { @Provides @Singleton User providerUser(){ return new User(); }}@Singleton@Component(modules ={UserModule.class})public interface MianComponent { void inject(MainActivity activity);}
- 通过在MianComponent modules 引入 UserMoudle和 DataInfoModule
@Singleton@Component(modules ={UserModule.class, DataInfoModule.class})//加载多个Moudlepublic interface MianComponent { void inject(MainActivity activity);}
注解@Named的使用
相当于用来区分多个实体类的别名两个构造函数
@Qualifier@Documented@Retention(RUNTIME)public @interface Named { /** The name. */ String value() default "";}
给UserModule中User不同的构造添加Named
@Module(includes = {DataInfoModule.class}) //includes 引入moudlepublic class UserModule { @Provides @Singleton User providerUser(){ return new User(); } @Named("userN") @Provides @Singleton User providerUserN(){ return new User("userN"); } @Named("userY") @Provides @Singleton User providerUserY(DataInfo data){ return new User(data,"userY"); }}
然后我们调用的时候也做标识区分
public class MainActivity extends AppCompatActivity { private final static String TAG="Dagger"; @Inject DataInfo dataInfo; @Named("userY") @Inject User userY;//使用Inject 注解获取实例化对象User @Named("userN") @Inject User userN; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); //依赖绑定 DaggerMianComponent.create().inject(this); userY.name="塞班"; userY.age=18; userN.name="阿巴阿巴"; userN.age=10; dataInfo.height=188; dataInfo.sex="nice"; //对象调用 Log.d(TAG,"userY="+userY+",tag="+userY.tag+",DataInfo="+dataInfo); Log.d(TAG,"userN="+userN+",tag="+userN.tag); }}
注解@Qualifier的使用
和@Named的作用类似,都是用来区分类型,可以自定义类型,只能是基本数据类型、String、Enum、Class,包含其一维数组
//Qualifier.java@Target(ANNOTATION_TYPE)@Retention(RUNTIME)@Documentedpublic @interface Qualifier {}//自定义QualifierType.java@Qualifier@Retention(RetentionPolicy.RUNTIME)public @interface QualifierType { String value() default ""; String value2() default "";}//UserModule.java中使用 @QualifierType ("vip")//默认的value一个属性@QualifierType (value2 = "nomal")//value2一个属性@QualifierType (value = "svip", value2 = "vip")//使用了两个属性
其他情况的应用
1.方法注入的应用:
此时@Sign不能注解在方法上,必须注解在对应的注入参数中。
@Inject public void injectUser(@QualifierType("vip") User user) { mUser= user; }
2.@Provides方法依赖关系的应用:
@QualifierType("svip") @Provides public Bus provideUserVipType(@QualifierType("vip") String nameType) { return new User(nameType); } @QualifierType("vip") @Provides public String provideNameType() { return "高级唯爱皮"; }
注意 build构建对象的两种方式
这里就算我们不使用 @Inject 注入User对象,也能通过Moudle中@Provides提供的User对象,注入Component 的 mianComponent生成创建的工厂类 DaggerMianComponent 获取对应的对象
MianComponent.java 添加getUser获取Moudle中的User对象
@Singleton@Component(modules ={UserModule.class})public interface MianComponent { User getuser(); void inject(MainActivity activity); @Component.Builder interface Builder{ @BindsInstance Builder appplication(Application application); MianComponent build(); }}
MainActivity.java 两种实例化获取方式
//1.Inject 注入方式的@InjectUser userDaggerMianComponent.builder().build().inject(this); //2.不使用Inject 注入方式的MianComponent mianComponent = DaggerMianComponent.builder().build();User user=mianComponent.getUser();
Android Studio Make Build 生成 DaggerMianComponent
public final class DaggerMianComponent implements MianComponent { private Provider providerUserProvider; private Provider providerUserProvider2; private Provider providerUserYProvider; private Provider providerUserNProvider; private MembersInjector mainActivityMembersInjector; private DaggerMianComponent(Builder builder) { assert builder != null; initialize(builder); } public static MianComponent.Builder builder() { return new Builder(); } @SuppressWarnings("unchecked") private void initialize(final Builder builder) { this.providerUserProvider = DoubleCheck.provider(UserModule_ProviderUserFactory.create(builder.userModule)); this.providerUserProvider2 = DoubleCheck.provider(DataInfoModule_ProviderUserFactory.create(builder.dataInfoModule)); this.providerUserYProvider = DoubleCheck.provider( UserModule_ProviderUserYFactory.create(builder.userModule, providerUserProvider2)); this.providerUserNProvider = DoubleCheck.provider(UserModule_ProviderUserNFactory.create(builder.userModule)); this.mainActivityMembersInjector = MainActivity_MembersInjector.create( providerUserProvider2, providerUserYProvider, providerUserNProvider); } @Override public User getuser() { return providerUserProvider.get(); } @Override public void inject(MainActivity activity) { mainActivityMembersInjector.injectMembers(activity); } private static final class Builder implements MianComponent.Builder { private UserModule userModule; private DataInfoModule dataInfoModule; private Application appplication; @Override public MianComponent build() { if (userModule == null) { this.userModule = new UserModule(); } if (dataInfoModule == null) { this.dataInfoModule = new DataInfoModule(); } if (appplication == null) { throw new IllegalStateException(Application.class.getCanonicalName() + " must be set"); } return new DaggerMianComponent(this); } @Override public Builder appplication(Application application) { this.appplication = Preconditions.checkNotNull(application); return this; } }}
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