0. 序言

• 之前写过一篇名为"看完不会写MVP架构我跪搓板"的博文，收到一些阅读者的建议，希望能够对Rxjava的生命周期进行管理以及添加Dagger到MVP架构中，所以今天抽一点时间写一篇拿来即可于实战的Demo。

1. 博文目录

• 添加依赖

• 创建项目基本目录

• 实现Model

• 定义契约接口NewsInfoContract

• 实现Presenter

• 实现View

• 补充网络配置代码

• 适配Android28网络请求

• 添加Dagger2

• 实现RetrofitManager单例

2. 添加依赖

    implementation 'com.squareup.retrofit2:retrofit:2.5.0'implementation 'com.squareup.retrofit2:converter-gson:2.5.0'implementation 'com.squareup.retrofit2:adapter-rxjava2:2.5.0'implementation 'io.reactivex.rxjava2:rxjava:2.2.4'implementation 'io.reactivex.rxjava2:rxandroid:2.1.0'implementation 'com.squareup.okhttp3:okhttp:3.12.0'implementation 'com.squareup.okhttp3:logging-interceptor:3.5.0'implementation 'com.trello.rxlifecycle2:rxlifecycle-android-lifecycle:2.2.1'
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3. 创建项目基本目录

4. 实现Model

• 创建实体类NewsInfo：

public class NewsInfo {private String reason;private ResultBean result;...public static class ResultBean {private String stat;private List<DataBean> data;...public static class DataBean {private String uniquekey;private String title;private String date;private String category;private String author_name;private String url;private String thumbnail_pic_s;private String thumbnail_pic_s02;private String thumbnail_pic_s03;...}}
}
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• 定义获取网络数据的接口类NetTask：

public interface NetTask {void execute(LifecycleProvider lifecycleProvider, String type, LoadTasksCallBack callBack);
}
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public interface LoadTasksCallBack {void OnSuccess(NewsInfo newsInfo);void OnStart();void onFailed();void onFinish();
}
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• 编写NetTask的实现类NewsInfoTask：

public class NewsInfoTask implements NetTask {private Disposable mDisposable;private NewsInfoTask() {}public static NewsInfoTask getInstance() {return NewsInfoTaskHolder.sNewsInfoFask;}private static class NewsInfoTaskHolder {private static final NewsInfoTask sNewsInfoFask = new NewsInfoTask();}@Overridepublic void execute(LifecycleProvider lifecycleProvider,String type, final LoadTasksCallBack callBack) {RetrofitManager.getInstance().getRetrofit(Constant.BASEURL).create(NewsService.class).getNewsInfo(type, BuildConfig.NewKey).subscribeOn(Schedulers.io()).observeOn(AndroidSchedulers.mainThread()).compose(lifecycleProvider.<Long>bindUntilEvent(Lifecycle.Event.ON_DESTROY)).subscribe(new Observer<NewsInfo>() {@Overridepublic void onSubscribe(Disposable disposable) {mDisposable= disposable;callBack.OnStart();}@Overridepublic void onNext(NewsInfo newsInfo) {callBack.OnSuccess(newsInfo);}@Overridepublic void onError(Throwable e) {callBack.onFailed();}@Overridepublic void onComplete() {callBack.onFinish();mDisposable.dispose();}});}
}
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6. 定义契约接口NewsInfoContract：

public interface NewsInfoContract {interface Presenter{void getNewsInfo(LifecycleProvider lifecycleProvider, String type);}interface View {void setNewsInfo(NewsInfo newsInfo);void showLoading();void hideLoading();void showError();}
}
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7. 实现Presenter

• 编写NewsInfoContract.Presenter接口的实现类NewsInfoPresenter：

public class NewsInfoPresenter implements NewsInfoContract.Presenter,LoadTasksCallBack {private NetTask mNetTask;private NewsInfoContract.View mView;public NewsInfoPresenter(NetTask netTask,NewsInfoContract.View view) {mNetTask = netTask;mView = view;}@Overridepublic void getNewsInfo(LifecycleProvider lifecycleProvider, String type) {mNetTask.execute(lifecycleProvider,type,this);}@Overridepublic void OnSuccess(NewsInfo newsInfo) {mView.setNewsInfo(newsInfo);}@Overridepublic void OnStart() {mView.showLoading();}@Overridepublic void onFailed() {mView.showError();mView.hideLoading();}@Overridepublic void onFinish() {mView.hideLoading();}
}
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6. 实现View

public class MainActivity extends AppCompatActivity implements NewsInfoContract.View {private NewsInfoContract.Presenter mPresenter = new NewsInfoPresenter(NewsInfoTask.getInstance(),this);LifecycleProvider<Lifecycle.Event> lifecycleProvider = AndroidLifecycle.createLifecycleProvider(this);private TextView mNew_Content;private Dialog mDialog;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);mNew_Content = findViewById(R.id.tv_content);mDialog = new ProgressDialog(this);mDialog.setTitle(R.string.dialog_get_info);findViewById(R.id.bt_get_news).setOnClickListener(v -> {mPresenter.getNewsInfo(lifecycleProvider,Constant.DEFAULT_TYPE);});}@Overridepublic void setNewsInfo(NewsInfo newsInfo) {if (newsInfo != null &amp;&amp; newsInfo.getResult() != null &amp;&amp; newsInfo.getResult().getData() != null) {mNew_Content.setText(newsInfo.getResult().getData().get(0).getTitle());}}@Overridepublic void showLoading() {mDialog.show();}@Overridepublic void hideLoading() {if (mDialog.isShowing())mDialog.dismiss();}@Overridepublic void showError() {Toast.makeText(this, R.string.toast_net_tip, Toast.LENGTH_SHORT).show();}}
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7. 补充网络配置代码

• Retrofit 管理类：

public class RetrofitManager {private static Retrofit sRetrofit = null;private static String sUrl = "";private static final int TIMEOUT = 20;private RetrofitManager() {}public static RetrofitManager getInstance() {return RetrofitManagerHolder.sInstance;}private static class RetrofitManagerHolder {private static final RetrofitManager sInstance = new RetrofitManager();}public Retrofit getRetrofit(String baseUrl) {sUrl = baseUrl;if (sRetrofit == null) {return create();} else {return sRetrofit;}}private Retrofit create() {HttpLoggingInterceptor loggingInterceptor = new HttpLoggingInterceptor();if (BuildConfig.DEBUG) {loggingInterceptor.setLevel(HttpLoggingInterceptor.Level.BODY);} else {loggingInterceptor.setLevel(HttpLoggingInterceptor.Level.BASIC);}OkHttpClient okHttpClient = new OkHttpClient.Builder().addInterceptor(loggingInterceptor).connectTimeout(TIMEOUT,TimeUnit.SECONDS).readTimeout(TIMEOUT, TimeUnit.SECONDS).writeTimeout(TIMEOUT, TimeUnit.SECONDS).retryOnConnectionFailure(true).build();sRetrofit = new Retrofit.Builder().baseUrl(sUrl).addConverterFactory(GsonConverterFactory.create()).addCallAdapterFactory(RxJava2CallAdapterFactory.create()).client(okHttpClient).build();return sRetrofit;}
}
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• 网络请求接口服务类NewsService：

public interface NewsService {@GET("toutiao/index")Observable<NewsInfo> getNewsInfo(@Query("type") String type, @Query("key")String key);
}
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8. 适配Android28网络请求

• 在res目录下创建名为xml的文件夹，并在文件夹里面创建名为network_security_config的xml文件：

<?xml version="1.0" encoding="utf-8"?>
<network-security-config><base-config cleartextTrafficPermitted="true" />
</network-security-config>
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• AndroidManifest配置文件中添加配置：

android:networkSecurityConfig="@xml/network_security_config"
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9. 添加Dagger2

9.0 分析

这里我们需要把NewsInfoTask和MainActivity注入到了Presenter中，把Presenter注入到了MainActivity中。

9.1 Dagger2实现NewsInfoTask单例

• 去掉NewsInfoTask以下代码：

    private NewsInfoTask() {}public static NewsInfoTask getInstance() {return NewsInfoTaskHolder.sNewsInfoFask;}private static class NewsInfoTaskHolder {private static final NewsInfoTask sNewsInfoFask = new NewsInfoTask();}
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• 新建名为NetTaskModule的Module：

@Module
public class NetTaskModule {@Singleton@Providespublic NetTask provideNewsInfoTask(){return new NewsInfoTask();}
}
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说明：生成NewsInfoTask的实例对象，并用@Singleton修饰。

• 新建名为NetTaskComponent的Component：

@Singleton
@Component(modules = NetTaskModule.class)
public interface NetTaskComponent {NetTask getNetTask();
}
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说明：
① NetTaskModule 中的方法provideNewsInfoTask用@Singleton修饰，NetTaskComponent也必须用@Singleton修饰。
② NetTaskComponent中不需要指明注入的目标，而需要提供实例对象的时候，可以用“NetTask getNetTask();”这种形式表示，指明返回的是NetTask，返回值很重要。

• 实现NewsInfoTask在App全局单例：
  @Singleton可以保证局部单例，即NetTaskComponent下的注入目标中NewsInfoTask的内存地址都是同一个，而一旦创建其他Component并关联NetTaskModule，此时创建出的NewsInfoTask的内存地址就会发生变化，所以保证全局单例我们只能初始化一次Component，而初始化的地方就是Application：

public class App extends Application {private NetTaskComponent mNetTaskComponent;@Overridepublic void onCreate() {super.onCreate();mNetTaskComponent = DaggerNetTaskComponent.builder().build();}public static App get(Context context){return (App)context.getApplicationContext();}public NetTaskComponent getNetTaskComponent() {return mNetTaskComponent;}
}
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说明：这里通过.builder().build()来获取NetTaskComponent。需要NewsInfoTask只通过NetTaskComponent，就可以保证NewsInfoTask对象的内存地址唯一了。

9.2 Presenter注入MainActivity

• @Inject修饰构造方法

    @Injectpublic NewsInfoPresenter(NewsInfoContract.View view,NetTask netTask) {mView = view;mNetTask = netTask;}
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说明：@Inject修饰构造方法意思是告诉Dagger2可以用这个构造方法构建NewsInfoPresenter。只有构造方法上有@Inject注解修饰，NewsInfoPresenter才可以对外提供实例对象。

• NewsInfoContract.View添加setPresenter方法

public interface NewsInfoContract {interface Presenter{void getNewsInfo(LifecycleProvider lifecycleProvider, String type);}interface View {void setNewsInfo(NewsInfo newsInfo);void showLoading();void hideLoading();void showError();void setPresenter(NewsInfoPresenter presenter);}
}
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• NewsInfoPresenter创建setPresenter方法，并用@Inject修饰

    @Injectvoid setPresenter(){mView.setPresenter(this);}
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说明：@Inject修饰方法的意思是方法注入，这里是把NewsInfoPresenter注入给MainActivity。方法注入是在构造方法后执行的。方法注入需要构造方法使用@Inject注解修饰，不然方法注入无法执行。

• MainActivity中用@Inject修饰变量NewsInfoPresenter：

    @InjectNewsInfoPresenter mPresenter;
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说明：@Inject修饰变量意思是NewsInfoPresenter需要依赖注入。

• MainActivity实现setPresenter方法

    @Overridepublic void setPresenter(NewsInfoPresenter presenter) {mPresenter = presenter;}
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综上：以上几步完成了Persenter注入到MainActivity。

9.3 NewsInfoTask和MainActivity注入到了Presenter

• 创建名为ActivityScoped的自定义Scope：

@Scope
@Documented
@Retention(RUNTIME)
public @interface ActivityScoped {
}
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• 创建NewsInfoModule的Module：

@Module
public class NewsInfoModule {private NewsInfoContract.View mView;public NewsInfoModule(NewsInfoContract.View view) {mView = view;}@Providespublic NewsInfoContract.View provideNewsInfoContractView() {return mView;}}
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说明：这里是为了将NewsInfoContract.View注入给MainActivity。

• 创建名为MainActivityComponent的Component：

@ActivityScoped
@Component(modules = NewsInfoModule.class,dependencies =NetTaskComponent.class)
public interface MainActivityComponent {void inject(MainActivity mainActivity);
}
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说明：
① dependencies意思是把NetTaskComponent的内容也拿过来注入。
② @ActivityScoped之所以创建自定义Scope是因为如果dependencies中的NetTaskComponent用了@Singleton修饰，这里就不能使用@Singleton修饰了。

• 修改MainActivity完成注入：

DaggerMainActivityComponent.builder().newsInfoModule(new NewsInfoModule(this)).netTaskComponent(App.get(this).getNetTaskComponent()).build().inject(this);
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说明：因为Presenter需要两个参数，所以这里一句话就把需要的两个参数传入了Presenter。我们看下DaggerMainActivityComponent的源码：

    public Builder newsInfoModule(NewsInfoModule newsInfoModule) {this.newsInfoModule = Preconditions.checkNotNull(newsInfoModule);return this;}public Builder netTaskComponent(NetTaskComponent netTaskComponent) {this.netTaskComponent = Preconditions.checkNotNull(netTaskComponent);return this;}
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说明：.newsInfoModule和.netTaskComponent接收Presenter需要的两个参数。然后看build()：

public MainActivityComponent build() {if (newsInfoModule == null) {throw new IllegalStateException(NewsInfoModule.class.getCanonicalName() + " must be set");}if (netTaskComponent == null) {throw new IllegalStateException(NetTaskComponent.class.getCanonicalName() + " must be set");}return new DaggerMainActivityComponent(this);}
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说明：这里把build()所在的Build传入了DaggerMainActivityComponent的构造方法，我们看下：

  private DaggerMainActivityComponent(Builder builder) {assert builder != null;initialize(builder);}
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说明：再看下initialize方法：

this.provideNewsInfoContractViewProvider =NewsInfoModule_ProvideNewsInfoContractViewFactory.create(builder.newsInfoModule);this.getNetTaskProvider =new Factory<NetTask>() {private final NetTaskComponent netTaskComponent = builder.netTaskComponent;@Overridepublic NetTask get() {return Preconditions.checkNotNull(netTaskComponent.getNetTask(),"Cannot return null from a non-@Nullable component method");}};this.newsInfoPresenterProvider =NewsInfoPresenter_Factory.create(newsInfoPresenterMembersInjector,provideNewsInfoContractViewProvider,getNetTaskProvider);
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说明：newsInfoModule得到provideNewsInfoContractViewProvider，netTaskComponent得到getNetTaskProvider，然后把两者，放入NewsInfoPresenter_Factory.create方法中：

  public static Factory<NewsInfoPresenter> create(MembersInjector<NewsInfoPresenter> newsInfoPresenterMembersInjector,Provider<NewsInfoContract.View> viewProvider,Provider<NetTask> netTaskProvider) {return new NewsInfoPresenter_Factory(newsInfoPresenterMembersInjector, viewProvider, netTaskProvider);}
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说明：再看NewsInfoPresenter_Factory

  public NewsInfoPresenter_Factory(MembersInjector<NewsInfoPresenter> newsInfoPresenterMembersInjector,Provider<NewsInfoContract.View> viewProvider,Provider<NetTask> netTaskProvider) {assert newsInfoPresenterMembersInjector != null;this.newsInfoPresenterMembersInjector = newsInfoPresenterMembersInjector;assert viewProvider != null;this.viewProvider = viewProvider;assert netTaskProvider != null;this.netTaskProvider = netTaskProvider;}
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说明：用viewProvider封装了NewsInfoContract.View；用netTaskProvider封装了NetTask。他们调用给了get方法：

  @Overridepublic NewsInfoPresenter get() {return MembersInjectors.injectMembers(newsInfoPresenterMembersInjector,new NewsInfoPresenter(viewProvider.get(), netTaskProvider.get()));}
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说明：看到这里，你会清晰的看到NetTask和MainActivity注入到了Presenter，而这个get方法何时调用的呢？我们看下inject方法：

  @Overridepublic void inject(MainActivity mainActivity) {mainActivityMembersInjector.injectMembers(mainActivity);}
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说明：再接着看injectMembers方法：

    @Overridepublic void injectMembers(MainActivity instance) {if (instance == null) {throw new NullPointerException("Cannot inject members into a null reference");}instance.mPresenter = mPresenterProvider.get();}
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说明：mPresenterProvider是谁呢：

private final Provider<NewsInfoPresenter> mPresenterProvider;
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说明：到这里会发现其实inject的目的就是把两个参数赋值给this中的presenter，而赋值离不开new，自然离不开构造方法，而构造方法那里也离不开@Inject。而这也正是Dagger2的原理所在，通过工厂方法把实例对象赋值给注入目标的用@Inject所修饰的成员变量。

10. 实现RetrofitManager单例

• 去除之前实现单例模式的以下代码

    private RetrofitManager() {}public static RetrofitManager getInstance() {return RetrofitManagerHolder.sInstance;}private static class RetrofitManagerHolder {private static final RetrofitManager sInstance = new RetrofitManager();}
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• NetTaskModule中添加以下方法：

    @Singleton@Providespublic RetrofitManager provideRetrofitManager(){return new RetrofitManager();}
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• NetTaskComponent中添加以下方法：

@Singleton
@Component(modules = NetTaskModule.class)
public interface NetTaskComponent {NetTask getNetTask();RetrofitManager getRetrofitManager();
}
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• 修改Applicaion的代码：

public class App extends Application {private static NetTaskComponent mNetTaskComponent;@Overridepublic void onCreate() {super.onCreate();mNetTaskComponent = DaggerNetTaskComponent.builder().build();}public static NetTaskComponent getNetTaskComponent() {return mNetTaskComponent;}
}
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说明：之前的方式需要传入Context，但是NewsInfoTask中并没有Context，所以我们这里修改为static，因为是单例模式，从创建就开始存在直到App应用程序退出，所以不会有内存泄露的情况。

• MainActivity和NewsInfoTask中修改获取NetTaskComponent的代码。

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