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;
@Module
public 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
@Module
public 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)
@Documented
public @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
@Module
public 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moudle
public 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Moudle
public 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moudle
public 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)
@Documented
public @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
@Inject
User user
DaggerMianComponent.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;
}
}
}