Dagger2生成代码解析

Dagger2生成代码解析

根据一个简单的Dagger2示例程序，进行进一步的探索，对Dagger2自动生成的代码进行解析。以下解析都基于该Demo生成的类进行。

UML

DaggerActivityComponent.Builder类

作用: 生成该类的父类 (DaggerActivityComponent)

public static final class Builder {
private ActivityModule activityModule;

private Builder() {
}

/*
* 生成Component实现类
*/
public ActivityComponent build() {
if (activityModule == null) {
this.activityModule = new ActivityModule();
}
return new DaggerActivityComponent(this); //Component:被装饰的类
}

/*
* 设置Module
*/
public Builder activityModule(ActivityModule activityModule) {
if (activityModule == null) {
throw new NullPointerException("activityModule");
}
this.activityModule = activityModule;
return this;
}
}

DaggerActivityComponent

作用: 初始化Provider，MembersInjector，关联Activity和Module，进行注入

@Generated("dagger.internal.codegen.ComponentProcessor")
public final class DaggerActivityComponent implements ActivityComponent {
private Provider<Person> provideUserModelProvider;
private MembersInjector<MainActivity> mainActivityMembersInjector;

private DaggerActivityComponent(Builder builder) {
assert builder != null;
initialize(builder);
}

public static Builder builder() {
return new Builder();
}

public static ActivityComponent create() {
return builder().build();
}

/*
* 进行初始化
*/
private void initialize(final Builder builder) {
this.provideUserModelProvider = ActivityModule_ProvideUserModelFactory.create(builder.activityModule);
this.mainActivityMembersInjector = MainActivity_MembersInjector.create((MembersInjector) MembersInjectors.noOp(), provideUserModelProvider);
}

/*
* 进行注入
*/
@Override
public void inject(MainActivity activity) {
mainActivityMembersInjector.injectMembers(activity);
}

public static final class Builder {
...
}
}

ActivityModule_ProvideUserModelFactory

Provides工厂，根据ActivityModule获取Person

@Generated("dagger.internal.codegen.ComponentProcessor")
public final class ActivityModule_ProvideUserModelFactory implements Factory<Person> {
private final ActivityModule module;

public ActivityModule_ProvideUserModelFactory(ActivityModule module) {
assert module != null;
this.module = module;
}

@Override
public Person get() {
Person provided = module.provideUserModel();
if (provided == null) {
throw new NullPointerException("Cannot return null from a non-@Nullable @Provides method");
}
return provided;
}

public static Factory<Person> create(ActivityModule module) {
return new ActivityModule_ProvideUserModelFactory(module);
}
}

MainActivity_MembersInjector

作用:对@Inject注释的变量进行赋值

@Generated("dagger.internal.codegen.ComponentProcessor")
public final class MainActivity_MembersInjector implements MembersInjector<MainActivity> {
private final MembersInjector<AppCompatActivity> supertypeInjector;
private final Provider<Person> personProvider;

public MainActivity_MembersInjector(MembersInjector<AppCompatActivity> supertypeInjector, Provider<Person> personProvider) {
assert supertypeInjector != null;
this.supertypeInjector = supertypeInjector;
assert personProvider != null;
this.personProvider = personProvider;
}

@Override
public void injectMembers(MainActivity instance) {
if (instance == null) {
throw new NullPointerException("Cannot inject members into a null reference");
}
supertypeInjector.injectMembers(instance);
instance.person = personProvider.get(); //赋值给MainActivity.person
}

public static MembersInjector<MainActivity> create(MembersInjector<AppCompatActivity> supertypeInjector, Provider<Person> personProvider) {
return new MainActivity_MembersInjector(supertypeInjector, personProvider);
}
}

多层依赖的情况

在多层依赖的情况下，最大的改变只是在MembersInjector的injectMembers中赋值部分添加了赋值的语句

@Override
public void injectMembers(MainActivity instance) {
if (instance == null) {
throw new NullPointerException("Cannot inject members into a null reference");
}
supertypeInjector.injectMembers(instance);
//以下为多层依赖情况下的赋值
instance.person = personProvider.get();
instance.shoppingCart = shoppingCartProvider.get();
}