安卓之MVP模式

      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();
}
}
}