Dagger2 Activity子作用域多綁定

參考文章：http://frogermcs.github.io/activities-multibinding-in-dagger-2/
在上一篇文章中，我對Dagger生成的源碼進行了分析替蛉，順便自定義了一下作用域贯溅，分析了作用域的實現(xiàn)原理。但是對于上一篇中自定義作用域這一塊兒躲查，還是有些不妥的它浅。原因有二：
1.Activity依賴于AppComponent，如果我們想要拿到Subcomponent镣煮，就必須得先拿到AppComponent對象姐霍，還是挺心煩的。
2.AppComponent必須得為所有的Subcomponent定義Factory: MainActivityComponent plus(MainActivityComponent.ModuleImpl module);

描述完了問題就來看看解決方案典唇。從Dagger2.7開始镊折，聲明Subcomponent的父作用域有了新的方案。

首先介衔，為所有的ActivityComponent的builder定義一個基本接口:

public interface ActivityComponentBuilder<M extends ActivityModule, C extends ActivityComponent> {
    ActivityComponentBuilder<M, C> activityModule(M activityModule);
    C build();
}

SubComponent可以是下面這樣：

@ActivityScope
@Subcomponent(
        modules = MainActivityComponent.MainActivityModule.class
)
public interface MainActivityComponent extends ActivityComponent<MainActivity> {

    @Subcomponent.Builder
    interface Builder extends ActivityComponentBuilder<MainActivityModule, MainActivityComponent> {
    }

    @Module
    class MainActivityModule extends ActivityModule<MainActivity> {
        MainActivityModule(MainActivity activity) {
            super(activity);
        }
    }
}

現(xiàn)在腌乡，我們希望有一個SubComponents的builders的集合，這樣我們在每個Activity中都可以獲取到需要的builder夜牡∮肱Γ可以用Multibinding的特性。

@Module(
        subcomponents = {
                MainActivityComponent.class,
                SecondActivityComponent.class
        })
public abstract class ActivityBindingModule {

    @Binds
    @IntoMap
    @ActivityKey(MainActivity.class)
    public abstract ActivityComponentBuilder mainActivityComponentBuilder(MainActivityComponent.Builder impl);

    @Binds
    @IntoMap
    @ActivityKey(SecondActivity.class)
    public abstract ActivityComponentBuilder secondActivityComponentBuilder(SecondActivityComponent.Builder impl);
}

ActivityBindingModule在AppComponent中創(chuàng)建塘装。因為這樣急迂，MainActivityComponent和SecondActivityComponent才能是AppComponent的SubComponents.
現(xiàn)在咱們可以注入SubComponent的builders的Map集合了:

public class MyApplication extends Application implements HasActivitySubcomponentBuilders {

    @Inject
    Map<Class<? extends Activity>, ActivityComponentBuilder> activityComponentBuilders;

    private AppComponent appComponent;

    public static HasActivitySubcomponentBuilders get(Context context) {
        return ((HasActivitySubcomponentBuilders) context.getApplicationContext());
    }

    @Override
    public void onCreate() {
        super.onCreate();
        appComponent = DaggerAppComponent.create();
        appComponent.inject(this);
    }

    @Override
    public ActivityComponentBuilder getActivityComponentBuilder(Class<? extends Activity> activityClass) {
        return activityComponentBuilders.get(activityClass);
    }
}

由于builders的Map集合沒必要一定要注入到Application中，所以咱們有一個額外的抽象蹦肴，HasActivitySubcomponentBuilders.

public interface HasActivitySubcomponentBuilders {
    ActivityComponentBuilder getActivityComponentBuilder(Class<? extends Activity> activityClass);
}

最后僚碎，Activity真正的實現(xiàn)就可以是下面這樣：

public class MainActivity extends BaseActivity {

    //...

    @Override
    protected void injectMembers(HasActivitySubcomponentBuilders hasActivitySubcomponentBuilders) {
        ((MainActivityComponent.Builder) hasActivitySubcomponentBuilders.getActivityComponentBuilder(MainActivity.class))
                .activityModule(new MainActivityComponent.MainActivityModule(this))
                .build().injectMembers(this);
    }
}

上面就是所需的所有代碼。現(xiàn)在來看看實現(xiàn)原理阴幌，走一遍流程會對整個過程更加清晰勺阐。
DaggerAppComponent:

public final class DaggerAppComponent implements AppComponent {
  private Provider<MainActivityComponent.Builder> mainActivityComponentBuilderProvider;

  private Provider<ActivityComponentBuilder> mainActivityComponentBuilderProvider2;

  private Provider<SecondActivityComponent.Builder> secondActivityComponentBuilderProvider;

  private Provider<ActivityComponentBuilder> secondActivityComponentBuilderProvider2;

  private Provider<Map<Class<? extends Activity>, Provider<ActivityComponentBuilder>>>
      mapOfClassOfAndProviderOfActivityComponentBuilderProvider;

  private MembersInjector<MyApplication> myApplicationMembersInjector;

  private Provider<Utils> provideUtilsProvider;

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

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

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

  @SuppressWarnings("unchecked")
  private void initialize(final Builder builder) {

    this.mainActivityComponentBuilderProvider =
        new Factory<MainActivityComponent.Builder>() {
          @Override
          public MainActivityComponent.Builder get() {
            return new MainActivityComponentBuilder();
          }
        };

    this.mainActivityComponentBuilderProvider2 = (Provider) mainActivityComponentBuilderProvider;

    this.secondActivityComponentBuilderProvider =
        new Factory<SecondActivityComponent.Builder>() {
          @Override
          public SecondActivityComponent.Builder get() {
            return new SecondActivityComponentBuilder();
          }
        };

    this.secondActivityComponentBuilderProvider2 =
        (Provider) secondActivityComponentBuilderProvider;

    this.mapOfClassOfAndProviderOfActivityComponentBuilderProvider =
        MapProviderFactory.<Class<? extends Activity>, ActivityComponentBuilder>builder(2)
            .put(MainActivity.class, mainActivityComponentBuilderProvider2)
            .put(SecondActivity.class, secondActivityComponentBuilderProvider2)
            .build();

    this.myApplicationMembersInjector =
        MyApplication_MembersInjector.create(
            mapOfClassOfAndProviderOfActivityComponentBuilderProvider);

    this.provideUtilsProvider =
        DoubleCheck.provider(AppModule_ProvideUtilsFactory.create(builder.appModule));
  }

  @Override
  public MyApplication inject(MyApplication application) {
    myApplicationMembersInjector.injectMembers(application);
    return application;
  }

  public static final class Builder {
    private AppModule appModule;

    private Builder() {}

    public AppComponent build() {
      if (appModule == null) {
        this.appModule = new AppModule();
      }
      return new DaggerAppComponent(this);
    }

    public Builder appModule(AppModule appModule) {
      this.appModule = Preconditions.checkNotNull(appModule);
      return this;
    }
  }

  private final class MainActivityComponentBuilder implements MainActivityComponent.Builder {
    private MainActivityComponent.MainActivityModule mainActivityModule;

    @Override
    public MainActivityComponent build() {
      if (mainActivityModule == null) {
        throw new IllegalStateException(
            MainActivityComponent.MainActivityModule.class.getCanonicalName() + " must be set");
      }
      return new MainActivityComponentImpl(this);
    }

    @Override
    public MainActivityComponentBuilder activityModule(
        MainActivityComponent.MainActivityModule activityModule) {
      this.mainActivityModule = Preconditions.checkNotNull(activityModule);
      return this;
    }
  }

  private final class MainActivityComponentImpl implements MainActivityComponent {
    private Provider<MainActivity> provideActivityProvider;

    private Provider<MainActivityPresenter> mainActivityPresenterProvider;

    private MembersInjector<MainActivity> mainActivityMembersInjector;

    private MainActivityComponentImpl(MainActivityComponentBuilder builder) {
      assert builder != null;
      initialize(builder);
    }

    @SuppressWarnings("unchecked")
    private void initialize(final MainActivityComponentBuilder builder) {

      this.provideActivityProvider =
          DoubleCheck.provider(
              ActivityModule_ProvideActivityFactory.create(builder.mainActivityModule));

      this.mainActivityPresenterProvider =
          DoubleCheck.provider(
              MainActivityPresenter_Factory.create(
                  provideActivityProvider, DaggerAppComponent.this.provideUtilsProvider));

      this.mainActivityMembersInjector =
          MainActivity_MembersInjector.create(mainActivityPresenterProvider);
    }

    @Override
    public void injectMembers(MainActivity arg0) {
      mainActivityMembersInjector.injectMembers(arg0);
    }
  }

  private final class SecondActivityComponentBuilder implements SecondActivityComponent.Builder {
    private SecondActivityComponent.SecondActivityModule secondActivityModule;

    @Override
    public SecondActivityComponent build() {
      if (secondActivityModule == null) {
        throw new IllegalStateException(
            SecondActivityComponent.SecondActivityModule.class.getCanonicalName() + " must be set");
      }
      return new SecondActivityComponentImpl(this);
    }

    @Override
    public SecondActivityComponentBuilder activityModule(
        SecondActivityComponent.SecondActivityModule activityModule) {
      this.secondActivityModule = Preconditions.checkNotNull(activityModule);
      return this;
    }
  }

  private final class SecondActivityComponentImpl implements SecondActivityComponent {
    private Provider<SecondActivity> provideActivityProvider;

    private Provider<SecondActivityPresenter> secondActivityPresenterProvider;

    private MembersInjector<SecondActivity> secondActivityMembersInjector;

    private SecondActivityComponentImpl(SecondActivityComponentBuilder builder) {
      assert builder != null;
      initialize(builder);
    }

    @SuppressWarnings("unchecked")
    private void initialize(final SecondActivityComponentBuilder builder) {

      this.provideActivityProvider =
          DoubleCheck.provider(
              ActivityModule_ProvideActivityFactory.create(builder.secondActivityModule));

      this.secondActivityPresenterProvider =
          DoubleCheck.provider(SecondActivityPresenter_Factory.create(provideActivityProvider));

      this.secondActivityMembersInjector =
          SecondActivity_MembersInjector.create(secondActivityPresenterProvider);
    }

    @Override
    public void injectMembers(SecondActivity arg0) {
      secondActivityMembersInjector.injectMembers(arg0);
    }
  }
}

咱們所需的代碼大部分都在這個類了。
老規(guī)矩矛双，先來看看是怎么調(diào)用注入的渊抽。

@Override
    protected void injectMembers(HasActivitySubcomponentBuilders hasActivitySubcomponentBuilders) {
        ((MainActivityComponent.Builder) hasActivitySubcomponentBuilders.getActivityComponentBuilder(MainActivity.class))
                .activityModule(new MainActivityComponent.MainActivityModule(this))
                .build()
                .injectMembers(this);
    }

此方法在BaseActivity中調(diào)用，傳入的hasActivitySubcomponentBuilders其實是Application（Application實現(xiàn)了HasActivitySubcomponentBuilders接口）议忽。調(diào)用Application的getActivityComponentBuilder方法懒闷，再把返回值強轉(zhuǎn)成MainActivityBuilder類型。來看看Application類:

public class MyApplication extends Application implements HasActivitySubcomponentBuilders {

    @Inject
    Map<Class<? extends Activity>, Provider<ActivityComponentBuilder>> activityComponentBuilders;

    private AppComponent appComponent;

    public static HasActivitySubcomponentBuilders get(Context context) {
        return ((HasActivitySubcomponentBuilders) context.getApplicationContext());
    }

    @Override
    public void onCreate() {
        super.onCreate();
        appComponent = DaggerAppComponent.create();
        appComponent.inject(this);
    }

    @Override
    public ActivityComponentBuilder getActivityComponentBuilder(Class<? extends Activity> activityClass) {
        return activityComponentBuilders.get(activityClass).get();
    }
}

OK,Application的get方法返回一個ActivityComponentBuilder實例，是從activityComponentBuilders集合中取出來的愤估。嘿帮辟？這個集合哪來的？往上看就發(fā)現(xiàn)玩焰，這個集合是通過依賴注入注入進來的由驹。
咱們回到DaggerAppComponent中看一眼，在initialize初始化方法中發(fā)現(xiàn)這么一句:

this.mapOfClassOfAndProviderOfActivityComponentBuilderProvider =
        MapProviderFactory.<Class<? extends Activity>, ActivityComponentBuilder>builder(2)
            .put(MainActivity.class, mainActivityComponentBuilderProvider2)
            .put(SecondActivity.class, secondActivityComponentBuilderProvider2)
            .build();

變量名夠直白了吧昔园，這是一個ActivityComponentBuilder和Activity class的映射表荔棉。把MainActivity和SecondActivity以及他們相應的Provider放到了集合當中。這句后面就是:

this.myApplicationMembersInjector =
        MyApplication_MembersInjector.create(
            mapOfClassOfAndProviderOfActivityComponentBuilderProvider);

創(chuàng)建了Injector蒿赢，把Map傳給他润樱。在Injector里面就走注入那套流程。
好羡棵，回到調(diào)用上來:

((MainActivityComponent.Builder) hasActivitySubcomponentBuilders.getActivityComponentBuilder(MainActivity.class))
                .activityModule(new MainActivityComponent.MainActivityModule(this))
                .build()
                .injectMembers(this);

現(xiàn)在我們知道壹若，傳一個MainActivity到getActivityComponentBuilder中，會從映射表中拿到MainActivity對應的ComponentBuilder返給我們皂冰。然后我們將它強轉(zhuǎn)為MainActivityComponent.Builder. 這個Builder也是一個接口店展，并且繼承自ActivityComponentBuilder:

@Subcomponent.Builder
    interface Builder extends ActivityComponentBuilder<MainActivityModule, MainActivityComponent> {
    }

MainActivityComponent的Module也是一個內(nèi)部類，也定義在MainActivityComponent中秃流。MainActivityComponentBuilder真正的實現(xiàn)也在DaggerAppComponent中赂蕴。

private final class MainActivityComponentBuilder implements MainActivityComponent.Builder {
    private MainActivityComponent.MainActivityModule mainActivityModule;

    @Override
    public MainActivityComponent build() {
      if (mainActivityModule == null) {
        throw new IllegalStateException(
            MainActivityComponent.MainActivityModule.class.getCanonicalName() + " must be set");
      }
      return new MainActivityComponentImpl(this);
    }

    @Override
    public MainActivityComponentBuilder activityModule(
        MainActivityComponent.MainActivityModule activityModule) {
      this.mainActivityModule = Preconditions.checkNotNull(activityModule);
      return this;
    }
  }

可以看到，咱們拿到了MainActivityComponent.Builder實例后舶胀，new一個MainActivityComponent.Module傳進去概说，然后調(diào)用build，build方法會創(chuàng)建一個MainActivityComponentImpl實例并返回:

private final class MainActivityComponentImpl implements MainActivityComponent {
    private Provider<MainActivity> provideActivityProvider;

    private Provider<MainActivityPresenter> mainActivityPresenterProvider;

    private MembersInjector<MainActivity> mainActivityMembersInjector;

    private MainActivityComponentImpl(MainActivityComponentBuilder builder) {
      assert builder != null;
      initialize(builder);
    }

    @SuppressWarnings("unchecked")
    private void initialize(final MainActivityComponentBuilder builder) {

      this.provideActivityProvider =
          DoubleCheck.provider(
              ActivityModule_ProvideActivityFactory.create(builder.mainActivityModule));

      this.mainActivityPresenterProvider =
          DoubleCheck.provider(
              MainActivityPresenter_Factory.create(
                  provideActivityProvider, DaggerAppComponent.this.provideUtilsProvider));

      this.mainActivityMembersInjector =
          MainActivity_MembersInjector.create(mainActivityPresenterProvider);
    }

    @Override
    public void injectMembers(MainActivity arg0) {
      mainActivityMembersInjector.injectMembers(arg0);
    }
  }

最后嚣伐，我們調(diào)用的是MainActivityComponentImpl的injectMembers的方法執(zhí)行注入糖赔。

以上就是解決開篇提到的兩個問題的方案:
1.Activity依賴于AppComponent，如果我們想要拿到Subcomponent轩端，就必須得先拿到AppComponent對象放典，還是挺心煩的。
2.AppComponent必須得為所有的Subcomponent定義Factory: MainActivityComponent plus(MainActivityComponent.ModuleImpl module);
老外管這個叫做Activities Subcomponents Multibinding, Activity子作用域多綁定...成功將子作用域和父作用域解耦基茵。

最后編輯于：2017.12.05 15:19:18

?著作權(quán)歸作者所有,轉(zhuǎn)載或內(nèi)容合作請聯(lián)系作者

人面猴
序言：七十年代末奋构，一起剝皮案震驚了整個濱河市，隨后出現(xiàn)的幾起案子拱层，更是在濱河造成了極大的恐慌弥臼，老刑警劉巖，帶你破解...
沈念sama閱讀 216,402評論 6贊 499
死咒
序言：濱河連續(xù)發(fā)生了三起死亡事件舱呻，死亡現(xiàn)場離奇詭異醋火，居然都是意外死亡悠汽，警方通過查閱死者的電腦和手機箱吕，發(fā)現(xiàn)死者居然都...
沈念sama閱讀 92,377評論 3贊 392
救了他兩次的神仙讓他今天三更去死
文/潘曉璐我一進店門芥驳，熙熙樓的掌柜王于貴愁眉苦臉地迎上來，“玉大人茬高，你說我怎么就攤上這事兆旬。” “怎么了怎栽？”我有些...
開封第一講書人閱讀 162,483評論 0贊 353
道士緝兇錄：失蹤的賣姜人
文/不壞的土叔我叫張陵丽猬，是天一觀的道長。經(jīng)常有香客問我熏瞄，道長脚祟，這世上最難降的妖魔是什么？我笑而不...
開封第一講書人閱讀 58,165評論 1贊 292
?港島之戀（遺憾婚禮）
正文為了忘掉前任强饮，我火速辦了婚禮由桌，結(jié)果婚禮上，老公的妹妹穿的比我還像新娘邮丰。我一直安慰自己行您，他們只是感情好，可當我...
茶點故事閱讀 67,176評論 6贊 388
惡毒庶女頂嫁案：這布局不是一般人想出來的
文/花漫我一把揭開白布剪廉。她就那樣靜靜地躺著娃循，像睡著了一般。火紅的嫁衣襯著肌膚如雪斗蒋。梳的紋絲不亂的頭發(fā)上捌斧，一...
開封第一講書人閱讀 51,146評論 1贊 297
城市分裂傳說
那天，我揣著相機與錄音泉沾，去河邊找鬼骤星。笑死，一個胖子當著我的面吹牛爆哑，可吹牛的內(nèi)容都是我干的洞难。我是一名探鬼主播，決...
沈念sama閱讀 40,032評論 3贊 417
雙鴛鴦連環(huán)套：你想象不到人心有多黑
文/蒼蘭香墨我猛地睜開眼揭朝，長吁一口氣：“原來是場噩夢啊……” “哼队贱！你這毒婦竟也來了？” 一聲冷哼從身側(cè)響起潭袱，我...
開封第一講書人閱讀 38,896評論 0贊 274
萬榮殺人案實錄
序言：老撾萬榮一對情侶失蹤柱嫌，失蹤者是張志新（化名）和其女友劉穎，沒想到半個月后屯换，有當?shù)厝嗽跇淞掷锇l(fā)現(xiàn)了一具尸體编丘，經(jīng)...
沈念sama閱讀 45,311評論 1贊 310
?護林員之死
正文獨居荒郊野嶺守林人離奇死亡与学，尸身上長有42處帶血的膿包…… 初始之章·張勛以下內(nèi)容為張勛視角年9月15日...
茶點故事閱讀 37,536評論 2贊 332
?白月光啟示錄
正文我和宋清朗相戀三年，在試婚紗的時候發(fā)現(xiàn)自己被綠了嘉抓。大學時的朋友給我發(fā)了我未婚夫和他白月光在一起吃飯的照片索守。...
茶點故事閱讀 39,696評論 1贊 348
活死人
序言：一個原本活蹦亂跳的男人離奇死亡，死狀恐怖抑片，靈堂內(nèi)的尸體忽然破棺而出卵佛，到底是詐尸還是另有隱情，我是刑警寧澤敞斋，帶...
沈念sama閱讀 35,413評論 5贊 343
?日本核電站爆炸內(nèi)幕
正文年R本政府宣布截汪，位于F島的核電站，受9級特大地震影響植捎，放射性物質(zhì)發(fā)生泄漏衙解。R本人自食惡果不足惜，卻給世界環(huán)境...
茶點故事閱讀 41,008評論 3贊 325
男人毒藥：我在死后第九天來索命
文/蒙蒙一焰枢、第九天我趴在偏房一處隱蔽的房頂上張望蚓峦。院中可真熱鬧，春花似錦医咨、人聲如沸枫匾。這莊子的主人今日做“春日...
開封第一講書人閱讀 31,659評論 0贊 22
一樁弒父案拟淮，背后竟有這般陰謀
文/蒼蘭香墨我抬頭看了看天上的太陽干茉。三九已至，卻和暖如春很泊，著一層夾襖步出監(jiān)牢的瞬間角虫，已是汗流浹背。一陣腳步聲響...
開封第一講書人閱讀 32,815評論 1贊 269
情欲美人皮
我被黑心中介騙來泰國打工委造，沒想到剛下飛機就差點兒被人妖公主榨干…… 1. 我叫王不留戳鹅，地道東北人。一個月前我還...
沈念sama閱讀 47,698評論 2贊 368
代替公主和親
正文我出身青樓昏兆，卻偏偏與公主長得像枫虏，于是被迫代替她去往敵國和親。傳聞我的和親對象是個殘疾皇子爬虱，可洞房花燭夜當晚...
茶點故事閱讀 44,592評論 2贊 353

Dagger2 Activity子作用域多綁定

推薦閱讀更多精彩內(nèi)容