作为一个码农，什么都不用多讲，贴代码

build project

build module

Application

public class App extends Application {    private AppComponent appComponent;    @Override public void onCreate() {        super.onCreate();        appComponent= DaggerAppComponent.builder()                .appModule(new AppModule(this))                .build();    }    public AppComponent getAppComponent() {        return appComponent;    }}

AppComponent

@Singleton@Component(modules = { AppModule.class })public interface AppComponent {    @ContextLife("Application")    App getApplication();    RetrofitHelper retrofitHelper();  //提供http的帮助类}

AppModule

@Modulepublic class AppModule {    private App application;    public AppModule(App application){        this.application=application;    }    @Provides    @Singleton    @ContextLife("Application")    public App provideApplication(){        return application;    }    @Provides    @Singleton    public RetrofitHelper provideRetrofitHelper() {        return new RetrofitHelper();    }}

ActivityComponent

@ActivityScope@Component(dependencies = AppComponent.class, modules = ActivityModule.class)//关联上下public interface ActivityComponent {    Activity getActivity();    void inject(LoginActivity loginActivity);//要在类中使用注入功能    void inject(MainActivity mainActivity);}

ActivityModule

@Modulepublic class ActivityModule {    private Activity mActivity;    public ActivityModule(Activity activity) {        this.mActivity = activity;    }    @Provides    @ActivityScope    public Activity provideActivity() {        return mActivity;    }    @Provides    @ActivityScope    public IPresenterFactory providePresenter(RetrofitHelper retrofitHelper) {        return new PresenterFactory(retrofitHelper);    }}

Base里面使用注入，否则无法注入

public abstract class PresenterActivity extends BaseActivity {    private final static String TAG = "PresenterActivity";    protected abstract void initInject();    @Override    protected void onCreate(@Nullable Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        initInject();    }    protected ActivityComponent getActivityComponent(){        return  DaggerActivityComponent.builder()                .appComponent(App.getInstance().getAppComponent())                .activityModule(getActivityModule())                .build();    }    private ActivityModule getActivityModule() {        return new ActivityModule(this);    }}

此时前提条件都有了

点击运行自动生成注入代码（没问题的前提）

使用注入：

public class MainActivity extends PresenterActivity {    @Inject    protected IPresenterFactory mPresenter;//没有创建对象，inject标签注入类型    private final int BASIC_PERMISSION_REQUEST_CODE = 100;    private TextView username;    @Override    public void findView() {        username = findView(R.id.username);        username.setText(App.getInstance().getUserEntity().getName()+" hello");    }    @Override    public void init() {        if (mPresenter != null){            Toasts.showShort("mPresenter success",context);//注入成功会打印出success        }    }    @Override    public int layoutResID() {        return R.layout.activity_main;    }    @Override    protected void initInject() {        getActivityComponent().inject(this);    }    @Subscribe(threadMode = ThreadMode.MAIN)    public void onEvent() {        Toasts.showShort("刷新UI",context);    }}