以前写程序都是MVC模式的，其实安卓自带的就是MVC模式，但现在觉得这种写法在后面随着项目越来越大，Activty或者Fragment中代码也会越来越多，导致项目的维护变的越来越复杂。所以需要另外一种架构模式来解决这个问题，发现适合Android开发的架构模式非MVP莫属了。
1.什么是MVP模式
MVP的M是指模型（model）、V是指视图（view）、P是指主持人（presenter），分别代表不同的模块。
模型（model）：就是处理业务逻辑的一块，进行数据的处理和存储，比如数据库操作，网络下载
视图（view）：是数据显示的一块，与用户进行交互
主持人（presenter）：就是用来连接模型（model）和视图（view）的桥梁，将模型和视图分开出来
如下图所示，View与Model并不直接交互，而是使用Presenter作为View与Model之间的桥梁。其中Presenter中同时持有Viwe层以及Model层的Interface的引用，而View层持有Presenter层Interface的引用。当View层某个界面需要展示某些数据的时候，首先会调用Presenter层的某个接口，然后Presenter层会调用Model层请求数据，当Model层数据加载成功之后会调用Presenter层的回调方法通知Presenter层数据加载完毕，最后Presenter层再调用View层的接口将加载后的数据展示给用户。这就是MVP模式的整个核心过程。
这样分层的好处就是大大减少了Model与View层之间的耦合度。一方面可以使得View层和Model层单独开发与测试，互不依赖。另一方面Model层可以封装复用，可以极大的减少代码量。当然，MVP还有其他的一些优点，这里不再赘述。下面看下MVP模式在具体项目中的使用。
下面我就通过RxJava、Retrofit一起实现MVP模式
首先我把我们网络数据的实体先写出来
public class UrlBean { private boolean error; private List<ResultsBean> results; public boolean isError() { return error; } public void setError(boolean error) { this.error = error; } public List<ResultsBean> getResults() { return results; } public void setResults(List<ResultsBean> results) { this.results = results; } public static class ResultsBean { private String _id; private String createdAt; private String desc; private String publishedAt; private String source; private String type; private String url; private boolean used; private String who; public String get_id() { return _id; } public void set_id(String _id) { this._id = _id; } public String getCreatedAt() { return createdAt; } public void setCreatedAt(String createdAt) { this.createdAt = createdAt; } public String getDesc() { return desc; } public void setDesc(String desc) { this.desc = desc; } public String getPublishedAt() { return publishedAt; } public void setPublishedAt(String publishedAt) { this.publishedAt = publishedAt; } public String getSource() { return source; } public void setSource(String source) { this.source = source; } public String getType() { return type; } public void setType(String type) { this.type = type; } public String getUrl() { return url; } public void setUrl(String url) { this.url = url; } public boolean isUsed() { return used; } public void setUsed(boolean used) { this.used = used; } public String getWho() { return who; } public void setWho(String who) { this.who = who; } } }在写一个接口
//这个接口是连接presenter和view public interface MainView<V> { void getDataSuccess(V view); void getFailMsg(String s); void showLoading(); void hideLoading(); }在将model层写出来，该层是通过RxJava和Retrofit封装的，如果对这两个还不了解的同学可以去看我关于 RxJava和Retrofit初级用法的博客
public interface ApiStores { //baseUrl String API_SERVER_URL = "http://gank.io/api/"; // http://gank.io/api/data/休息视频/10/1 @GET("data/{shiping}/{month}/{day}") Observable<UrlBean> getUser(@Path("shiping") String shiping,@Path("month") String month,@Path("day") String day); } public class AppClient { public static Retrofit mRetrofit; public static Retrofit retrofit() { if (mRetrofit == null) { OkHttpClient.Builder builder = new OkHttpClient.Builder(); if (BuildConfig.DEBUG) { // Log信息拦截器 HttpLoggingInterceptor loggingInterceptor = new HttpLoggingInterceptor(); loggingInterceptor.setLevel(HttpLoggingInterceptor.Level.BODY); //设置 Debug Log 模式 builder.addInterceptor(loggingInterceptor); } OkHttpClient okHttpClient = builder.build(); mRetrofit = new Retrofit.Builder() .baseUrl(ApiStores.API_SERVER_URL) .addConverterFactory(GsonConverterFactory.create()) .addCallAdapterFactory(RxJavaCallAdapterFactory.create()) .client(okHttpClient) .build(); } return mRetrofit; } } public abstract class ApiCallback<M> extends Subscriber<M> { public abstract void onSuccess(M model); public abstract void onFailure(int code, String msg); public abstract void onFinish(); @Override public void onError(Throwable e) { e.printStackTrace(); if (e instanceof HttpException) { HttpException httpException = (HttpException) e; //httpException.response().errorBody().string() int code = httpException.code(); String msg = httpException.getMessage(); Log.d("asdas","code=" + code); if (code == 504) { msg = "网络不给力"; } if (code == 502 || code == 404) { msg = "服务器异常，请稍后再试"; } onFailure(code, msg); } else { onFailure(0, e.getMessage()); } onFinish(); } @Override public void onNext(M model) { onSuccess(model); } @Override public void onCompleted() { onFinish(); } }
然后再是pesenter层
public class BasePresenter<V> { public V view; protected ApiStores apiStores; private CompositeSubscription mCompositeSubscription; public void attachView(V view){ this.view=view; apiStores = AppClient.retrofit().create(ApiStores.class); }; public void detachView() { this.view = null; onUnsubscribe(); } //RXjava取消注册，以避免内存泄露 public void onUnsubscribe() { if (mCompositeSubscription != null && mCompositeSubscription.hasSubscriptions()) { mCompositeSubscription.unsubscribe(); } } public void addSubscription(Observable observable, Subscriber subscriber) { if (mCompositeSubscription == null) { mCompositeSubscription = new CompositeSubscription(); } mCompositeSubscription.add(observable .subscribeOn(Schedulers.io()) .observeOn(AndroidSchedulers.mainThread()) .subscribe(subscriber)); } } public class MainPresenter extends BasePresenter<MainView>{ public MainPresenter(MainView view) { attachView(view); } public void loadData(String a,String b,String c) { view.showLoading(); addSubscription(apiStores.getUser(a,b,c), new ApiCallback<UrlBean>() { @Override public void onSuccess(UrlBean model) { view.getDataSuccess(model); } @Override public void onFailure(int code, String msg) { view.getFailMsg(msg); } @Override public void onFinish() { view.hideLoading(); } }); } } 最后是view层
public class MainActivity extends Activity implements MainView { @InjectView(R.id.tv_1) TextView text; private MainPresenter mainPresenter; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); ButterKnife.inject(this); mainPresenter=new MainPresenter(this); mainPresenter.loadData("休息视频","10","10"); } @Override public void getDataSuccess(Object view) { //在这里获取数据的对象，加载到界面，这里就不写了 UrlBean user= (UrlBean) view; for (int i=0;i<user.getResults().size();i++){ Log.e("url",user.getResults().get(i).getUrl().toString()); } } @Override public void getFailMsg(String s) { //错误信息 } @Override public void showLoading() { //加载动画 } @Override public void hideLoading() { //取消动画 } @Override protected void onDestroy() { super.onDestroy(); if (mainPresenter != null) { mainPresenter.detachView(); } } }
