Android Mvp案例解析

后端数据接口

接口地址：https://apis.tianapi.com/caipu/index

请求示例：https://apis.tianapi.com/caipu/index?key=你的APIKEY&word=黄瓜

支持协议：http/https

请求方式：get/post

返回格式：utf-8 json

数据格式

{"code": 200,"msg": "success","result": {"curpage": 1,"allnum": 5,"newslist": [{"id": "90e761e707dd996c431992c8e2a0a88b","ctime": "2023-07-07 08:29","title": "为避免轨道碰撞 SpaceX星链卫星6个月内“让路”","description": "7月7日消息，在过去6个月里，为了避免轨道碰撞，埃隆·马斯克（ElonMusk）旗下SpaceX公司的星链卫星机动次数激增，这引发了人们对卫星长期可持续性运行的担忧，因为未来几年将有数万颗新卫星进入轨道。在最近向美国联邦通信委员会（FCC...[]","source": "网易科技","picUrl": "https://nimg.ws.126.net/?url=http%3A%2F%2Fcms-bucket.ws.126.net%2F2023%2F0707%2F0f703849p00rxeh90001cc0009c0070c.png&thumbnail=200y140&quality=100&type=jpg","url": "https://www.163.com/tech/article/I91GDFVG00097U81.html"},{"id": "e8e49d6dd77be1a6ea82929a14abe6ef","ctime": "2023-07-07 06:32","title": "推特指责 Meta 挖角员工创建 Threads","description": "","source": "网易科技","picUrl": "https://nimg.ws.126.net/?url=http%3A%2F%2Fbjnewsrec-cv.ws.126.net%2Flittle730693cc23fj00rxebr3004xc000fw00lcg.jpg&thumbnail=200y140&quality=100&type=jpg","url": "https://www.163.com/dy/article/I919NRS10511B8LM.html"},{"id": "55cf44c545e02e8d9fc30e8b07980d3d","ctime": "2023-07-06 21:08","title": "分析人士：Meta的Threads对马斯克的Twitter构成","description": "","source": "网易科技","picUrl": "https://nimg.ws.126.net/?url=http%3A%2F%2Fbjnewsrec-cv.ws.126.net%2Flittle32088c42c3cj00rxdlrp000xc000sg00hgg.jpg&thumbnail=200y140&quality=100&type=jpg","url": "https://www.163.com/dy/article/I909EBMH0511B8LM.html"},{"id": "0bbc1f1f13121586804bb72e245448b2","ctime": "2023-07-06 20:26","title": "中国电信研究院副院长李安民：发展元宇宙，要提","description": "","source": "网易科技","picUrl": "https://nimg.ws.126.net/?url=http%3A%2F%2Fbjnewsrec-cv.ws.126.net%2Flittle64910ee1b6bj00rxctez005jd000j600anp.jpg&thumbnail=200y140&quality=100&type=jpg","url": "https://www.163.com/dy/article/I9071U0D0519DFFO.html"},{"id": "1962b01db3569398109fe336d5f8ff29","ctime": "2023-07-06 20:42","title": "XR“失宠”？头显出货量下降超三成，元宇宙再降","description": "","source": "网易科技","picUrl": "https://nimg.ws.126.net/?url=http%3A%2F%2Fbjnewsrec-cv.ws.126.net%2Flittle252508775e3j00rxdev60080c000se00fsg.jpg&thumbnail=200y140&quality=100&type=jpg","url": "https://www.163.com/dy/article/I907V12305199NPP.html"}]}
}

App客户端

MVP规范接口：IView、IModel、IPresenter，用于规范接口

package com.xzln.eatwhatjava.view;public interface IView {}  // 用于规范View层接口

package com.xzln.eatwhatjava.model;public interface IModel {}  // 用于规范Model层接口

package com.xzln.eatwhatjava.presenter;import com.xzln.eatwhatjava.view.IView;/*** 抽离公共接口*      所有的P层对象都公有* 	    而V层和M层对象则都是根据具体的业务进行定制* @param <V>*/
public interface IPresenter<V extends IView> {/*** 依附生命view* @param view v层对象*/void attachView(V view);/*** 分离View*/void detachView();/*** 判断View是否已经销毁* @return 是否销毁*/boolean isViewAttached();
}

回调规范接口：ICallBack

package com.xzln.eatwhatjava.contact;public interface ICallBack<T, K> {void onSuccess(T data);void onFail(K data);
}

布局逻辑

ViewPager2+Fragment

其中Fragment由refreshLayout+RecycleView组成，RecycleView放新闻条目。

ViewPager2用于对新闻进行分类

主界面布局

// activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"xmlns:app="http://schemas.android.com/apk/res-auto"xmlns:tools="http://schemas.android.com/tools"android:layout_width="match_parent"android:layout_height="match_parent"tools:context=".view.MainActivity"android:orientation="vertical"><com.google.android.material.tabs.TabLayoutandroid:id="@+id/tab_layout"android:layout_width="match_parent"android:layout_height="40dp"android:background="@color/colorPrimary"app:tabGravity="fill"app:tabMode="fixed"app:tabTextColor="@android:color/white" /><androidx.viewpager2.widget.ViewPager2android:id="@+id/view_pager2"android:layout_width="match_parent"android:layout_height="match_parent" />
</LinearLayout>

M（Model）

// INewsModel.java
package com.xzln.eatwhatjava.model;import com.xzln.eatwhatjava.contact.ICallBack;/*** 定义规范接口：（新闻）*      单一接口的M层*/
public interface INewsModel extends IModel {// post请求void getData(int page, int num, final ICallBack callback);
}

// NewsModel.java
package com.xzln.eatwhatjava.model;import android.util.Log;import com.xzln.eatwhatjava.api.NewsApi;
import com.xzln.eatwhatjava.bean.NewsListBean;
import com.xzln.eatwhatjava.bean.Result;
import com.xzln.eatwhatjava.config.NewsConfig;
import com.xzln.eatwhatjava.contact.ICallBack;
import com.xzln.eatwhatjava.utils.RetrofitUtils;import io.reactivex.Observable;
import io.reactivex.Observer;
import io.reactivex.android.schedulers.AndroidSchedulers;
import io.reactivex.disposables.Disposable;
import io.reactivex.schedulers.Schedulers;
/*** 定义了News功能模块的M层类*       调用retrofit网络API，通过CallBack将数据传到P层* TODO: onNext中发生错误的情况 和 onError中发生错误的情况 都有哪些*/
public class NewsModel implements INewsModel {public static final String TAG = "com.xzln.eatwhatjava.model.NewsModel";@Overridepublic void getData(int page, int num, ICallBack callback) {fetchKejiNews(page, num).observeOn(AndroidSchedulers.mainThread())  // Android 主线程观察.subscribeOn(Schedulers.io())   // 消费.subscribe(new Observer<Result<NewsListBean>>() { // URL访问成功@Overridepublic void onSubscribe(Disposable d) {}@Overridepublic void onNext(Result<NewsListBean> newsListBeanResult) {  // 数据迭代器?if (null == newsListBeanResult) { callback.onFail("出现错误: null == newsListBeanResult"); } else if (newsListBeanResult.getCode() != 200) { callback.onFail(newsListBeanResult.getMsg());} else { callback.onSuccess(newsListBeanResult); }}@Overridepublic void onError(Throwable e) {  // 访问错误或者数据解析错误e.printStackTrace();callback.onFail("出现错误: onError");}@Overridepublic void onComplete() { Log.d(TAG, "onComplete"); }});}protected Observable<Result<NewsListBean>> fetchKejiNews(int page, int num) {return RetrofitUtils.getRetrofit().create(NewsApi.class).fetchKejiNews(NewsConfig.getKejiNewsFieldMap(page, num));}
}

V（View）

// INewsView.java
package com.xzln.eatwhatjava.view;import com.xzln.eatwhatjava.presenter.IPresenter;/*** 定义News功能模块的View类的规范接口*      （P层和V层的桥梁）* @param <P> P层对象类型* @param <T> P层访问成功时返回的类型* @param <V> P层访问失败时返回的类型*/
public interface INewsView<P extends IPresenter, T, V> extends IView{void showNewsSuccess(T newsBeans);void showNewsFail(V data);
}

package com.xzln.eatwhatjava.base;import android.os.Bundle;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;import com.xzln.eatwhatjava.presenter.IPresenter;
import com.xzln.eatwhatjava.view.IView;/*** 抽象类，Fragment的公共抽象类* @param <P>*/
public abstract class BaseFragment<P extends IPresenter> extends Fragment implements IView {protected P mPresenter;  // P层对象，用于和V层、M层进行联系protected View mView;  // V层对象，通过V层对象完成P和V之间的联系/*** 完成P层对象的创建和初始化* @param savedInstanceState If the fragment is being re-created from* a previous saved state, this is the state.*/@Overridepublic void onCreate(@Nullable Bundle savedInstanceState) {super.onCreate(savedInstanceState);initPresenter();init();}/**** @param inflater The LayoutInflater object that can be used to inflate* any views in the fragment,* @param container If non-null, this is the parent view that the fragment's* UI should be attached to.  The fragment should not add the view itself,* but this can be used to generate the LayoutParams of the view.* @param savedInstanceState If non-null, this fragment is being re-constructed* from a previous saved state as given here.** @return 视图对象*/@Overridepublic View onCreateView(LayoutInflater inflater, ViewGroup container,Bundle savedInstanceState) {// Inflate the layout for this fragmentmView = inflater.inflate(getLayoutId(), container, false);return mView;}/*** Fragment销毁时，先取消P层对象和Fragment的绑定，避免空指针异常*/@Overridepublic void onDestroy() {if (mPresenter != null && mPresenter.isViewAttached()) {mPresenter.detachView();}super.onDestroy();}/*** 创建和初始化P层对象，将P层对象生命周期与当前Fragment绑定*/protected void initPresenter() {mPresenter = createPresenter();//绑定生命周期if (mPresenter != null) {mPresenter.attachView(this);}}/*** 抽象方法，由子类根据对应的布局来实现，返回其布局ID，用于Fragment的OnCreateView* @return 布局ID*/public abstract int getLayoutId();/*** 创建一个Presenter** @return P层对象*/protected abstract P createPresenter();/*** 用于子类的其他数据的初始化*/protected abstract void init();}

//NewsFragment.java
package com.xzln.eatwhatjava.view;import android.os.Bundle;
import android.os.Handler;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
import androidx.swiperefreshlayout.widget.SwipeRefreshLayout;import com.xzln.eatwhatjava.R;
import com.xzln.eatwhatjava.adapter.NewsRecycleViewAdapter;
import com.xzln.eatwhatjava.base.BaseFragment;
import com.xzln.eatwhatjava.bean.NewsBean;
import com.xzln.eatwhatjava.presenter.NewsPresenter;import java.util.LinkedList;
import java.util.List;/*** News的布局碎片*/
public class NewsFragment extends BaseFragment<NewsPresenter> implements INewsView<NewsPresenter, List<NewsBean>, String> {private static final String TAG = "com.xzln.eatwhatjava.view.NewsFragment";protected int mNewsType;  // News的类别，由创建者传入protected SwipeRefreshLayout mSwipeRefreshLayout;  // 顶部的刷新布局protected RecyclerView mRecycleView;protected List<NewsBean> mNewsBeans;  // 数据列表protected int mCurPage = 0;  // 当前页码protected int mNumOfPage = 25;  // 每页中数据数目protected NewsRecycleViewAdapter mNewsRecycleViewAdapter;  // RecycleView适配器protected LinearLayoutManager mLinearLayoutManager;private int mTotalItemCount;/*recycleView下的总item数目*/private int mFirstVisibleItem;/*当前可见区内最后一个item的position*/private int mLastVisibleItem;/*当前可见区内最后一个item的position*//*Return the current number of child views attached to the parent RecyclerView.*/private int mVisibleItemCount;/*当前recycleView下可见的item数*/public NewsFragment(int newsType) {  mNewsType = newsType; }/*** 刷新时调用：页码清零、数据清空、重新获取数据*/protected void refreshView() {mCurPage = 0;mNewsBeans.clear();mNewsRecycleViewAdapter.clearData();mPresenter.getNewsData(mCurPage++, mNumOfPage);}@Nullable@Overridepublic View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {return super.onCreateView(inflater, container, savedInstanceState);}@Overridepublic void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {super.onViewCreated(view, savedInstanceState);mSwipeRefreshLayout = mView.findViewById(R.id.layout_swipe_refresh);mRecycleView = mView.findViewById(R.id.view_recycle);// mPresenter.getNewsData(mCurPage++, mNumOfPage);refreshView();setupListener();}/*** 用于创建P层对象，由子类具体定制实现* @return P层对象*/@Overrideprotected NewsPresenter<NewsFragment> createPresenter() { return new NewsPresenter<>(this); }/*** 由子类定制，用于完成子类中的数据初始化*  视图id的绑定不可在这完成。因为视图View对象的生成在OnCreateView，而init函数在OnCreate中*/@Overrideprotected void init() {mNewsBeans = new LinkedList<>();mNewsRecycleViewAdapter = new NewsRecycleViewAdapter(getActivity(), mNewsBeans);}/*** @return 视图布局文件的ID*/@Overridepublic int getLayoutId() { return R.layout.activity_fragment_main; }/*** 启动监听器* 1. 刷新头* 2. RecycleView适配器、布局管理器*/private void setupListener() {mSwipeRefreshLayout.setOnRefreshListener(new SwipeRefreshLayout.OnRefreshListener() {@Overridepublic void onRefresh() {Log.d(TAG, "mSwipeRefreshLayout.setOnRefreshListener.onRefresh");
//                mSwipeRefreshLayout.setRefreshing(false);refreshView();new Handler().postDelayed(new Runnable() {@Overridepublic void run() { mSwipeRefreshLayout.setRefreshing(false); }},2000);}});mLinearLayoutManager = new LinearLayoutManager(getActivity());mRecycleView.setLayoutManager(mLinearLayoutManager);mRecycleView.setAdapter(mNewsRecycleViewAdapter);/*recycleView*/mRecycleView.addOnScrollListener(new RecyclerView.OnScrollListener() {@Overridepublic void onScrollStateChanged(@NonNull RecyclerView recyclerView, int newState) {super.onScrollStateChanged(recyclerView, newState);Log.d(TAG, "onScrollStateChanged  -->  newState" + newState);// 获取数据逻辑// 滚动状态改变 && 最后一个position + 1 >= totalif (newState == RecyclerView.SCROLL_STATE_DRAGGING &&mLastVisibleItem + 1 >= mTotalItemCount &&mVisibleItemCount <= mTotalItemCount) {mPresenter.getNewsData(mCurPage++, mNumOfPage);}@Overridepublic void onScrolled(@NonNull RecyclerView recyclerView, int dx, int dy) {super.onScrolled(recyclerView, dx, dy);mLinearLayoutManager.findFirstVisibleItemPosition();mTotalItemCount = mLinearLayoutManager.getItemCount();mFirstVisibleItem = mLinearLayoutManager.findFirstVisibleItemPosition();mLastVisibleItem = mLinearLayoutManager.findLastVisibleItemPosition();/*当前可见区内最后一个item的position*//*Return the current number of child views attached to the parent RecyclerView.*/mVisibleItemCount = mLinearLayoutManager.getChildCount();/*当前recycleView下可见的item数*/}});}/*** 与P层联系的函数* @param newsBeans P层成功返回的数据*/@Overridepublic void showNewsSuccess(List<NewsBean> newsBeans) {Log.d(TAG, "showNewsSuccess  newsBeans.size()=" + newsBeans.size());mNewsRecycleViewAdapter.addData(newsBeans);}/*** 与P层联系的函数* @param data P层失败返回的数据*/@Overridepublic void showNewsFail(String data) {Log.d(TAG, "showNewsSuccess");}
}

P（Presenter）

// IPresenter.java
package com.xzln.eatwhatjava.presenter;import com.xzln.eatwhatjava.view.IView;/*** 抽离公共接口*      所有的P层对象都公有* @param <V>*/
public interface IPresenter<V extends IView> {/*** 依附生命view* @param view v层对象*/void attachView(V view);/*** 分离View*/void detachView();/*** 判断View是否已经销毁* @return 是否销毁*/boolean isViewAttached();
}

// BasePresenter.java
package com.xzln.eatwhatjava.base;import com.xzln.eatwhatjava.presenter.IPresenter;
import com.xzln.eatwhatjava.view.IView;/*** IPresenter接口需要所有的P层实现类继承* 对于生命周期这部分功能P层都是通用的,因此可以抽出来一个抽象基类BasePresenter,去实现IPresenter的接口.* @param <V>*/
public abstract class BasePresenter<V extends IView> implements IPresenter<V> {protected V mView;@Overridepublic void attachView(V view) { mView = view; }@Overridepublic void detachView() { mView = null; }@Overridepublic boolean isViewAttached() { return mView != null; }
}

P层对象中持有V层对象和M层对象
P层调用M层获取数据，并设置CallBack。通过CallBack完成M层和P层间的联系。
在CallBack中调用View对象，完成P层与V层的联系。

// NewsPresenter.java
package com.xzln.eatwhatjava.presenter;import android.util.Log;import com.xzln.eatwhatjava.base.BasePresenter;
import com.xzln.eatwhatjava.bean.NewsListBean;
import com.xzln.eatwhatjava.bean.Result;
import com.xzln.eatwhatjava.contact.ICallBack;
import com.xzln.eatwhatjava.model.INewsModel;
import com.xzln.eatwhatjava.model.NewsModel;
import com.xzln.eatwhatjava.view.INewsView;
import com.xzln.eatwhatjava.view.IView;/*** News功能模块P层逻辑* @param <V>*/
public class NewsPresenter<V extends IView> extends BasePresenter<V> {private static final String TAG = "com.xzln.eatwhatjava.presenter.NewsPresenter";protected INewsView mNewsView;protected INewsModel mNewsModel;public NewsPresenter(V view) {mNewsView = (INewsView) view;createModel();}private void createModel() {if (mNewsModel == null) { mNewsModel = new NewsModel(); }}public void getNewsData(int page, int num) {mNewsModel.getData(page, num,new ICallBack<Result<NewsListBean>, String>() {  // P层定义CallBack，从而将数据从@Overridepublic void onSuccess(Result<NewsListBean> data) {Log.d(TAG, ".getData.onSuccess");mNewsView.showNewsSuccess(data.getResult().getNewslist());}@Overridepublic void onFail(String data) {mNewsView.showNewsFail("数据获取失败");Log.d(TAG, ".getData.onFail -->  " + data);}});}
}

// ICallBack.java
package com.xzln.eatwhatjava.contact;public interface ICallBack<T, K> {void onSuccess(T data);void onFail(K data);
}

Okhttp+Retrofit+RxJava网络http请求

RetrofitUtil

//RetrofitUtils.java
package com.xzln.eatwhatjava.utils;import com.xzln.eatwhatjava.config.NewsConfig;import java.util.concurrent.TimeUnit;import okhttp3.OkHttpClient;
import retrofit2.Retrofit;
import retrofit2.adapter.rxjava2.RxJava2CallAdapterFactory;
import retrofit2.converter.gson.GsonConverterFactory;public class RetrofitUtils {private static Retrofit retrofit;private static OkHttpClient okhttp;/*** 自定义okhttp客户端** @return okhttp客户端*/public static OkHttpClient getOkhttp() {if (okhttp == null) {synchronized (RetrofitUtils.class) {if (okhttp == null) {okhttp = new OkHttpClient.Builder().connectTimeout(15, TimeUnit.SECONDS).readTimeout(15, TimeUnit.SECONDS).writeTimeout(15, TimeUnit.SECONDS).build();}}}return okhttp;}/*** 单例retrofit客户端** @return retrofit客户端*/public static Retrofit getRetrofit() {if (retrofit == null) {synchronized (RetrofitUtils.class) {if (retrofit == null) {retrofit = new Retrofit.Builder().baseUrl(NewsConfig.newsBaseUrl).addCallAdapterFactory(RxJava2CallAdapterFactory.create()).addConverterFactory(GsonConverterFactory.create()).client(getOkhttp()).build();}}}return retrofit;}
}

//NewsApi.java
package com.xzln.eatwhatjava.api;import com.xzln.eatwhatjava.bean.NewsListBean;
import com.xzln.eatwhatjava.bean.Result;import java.util.Map;
import io.reactivex.Observable;
import retrofit2.http.FieldMap;
import retrofit2.http.FormUrlEncoded;
import retrofit2.http.POST;public interface NewsApi {// POST请求数据@FormUrlEncoded@POST("keji/index")Observable<Result<NewsListBean>> fetchKejiNews(@FieldMap Map<String, Object> map);
//    Observable<Result<List<NewsBean>>> fetchKejiNews(@FieldMap Map<String, Object> map);
}

---

Mvp架构-初学者

MVP架构是为了让各个模块之间降低耦合，方便维护，也可以让代码更简洁，让代码简洁的意思是让代码更清晰，并不是让代码更少；MVP契约者是为了进一步的低耦合、接口统一管理。

MVP对接口灵活的调用可以轻松的应对产品的变更。

presenter 类与View 和 Model 通信，做到视图和逻辑的解耦。

MVP架构的契约者

TODO