一、什么是MVP

MVP:全称 Model-View-Presenter。

MVP框架由3部分组成：View层负责显示，Presenter层负责逻辑处理，Model层提供数据。

View:负责绘制UI元素、与用户进行交互(在Android中体现为Activity,Fragment)

Model:负责存储、检索、操纵数据

Presenter:作为View与Model交互的中间纽带，处理与用户交互的负责逻辑。

二、创建Model Presenter View三个包

三、代码编写

1.View层代码

view层负责界面操作,如何确定view层里面有那些操作呢?
拿我这个UserView举例.
onLogin代表登录时候要做的事情,比如显示一个进度dialog
loginSuccess代表登录成功后要做的事情,做界面跳转等操作
loginFail表示登录失败后得操作,显示一个Toast等

public interface  UserView{
    void onLogin();
    void loginSuccess(UserBean bean);
    void loginFail(Exception e,int code);
}

2.Presenter层代码

这层主要负责View层和Model层的连接,也有中间人得意思,
View层请求Presenter层,Presenter在请求Model层,Model层处理数据之后通过回调接口传递给Presenter层,Presenter在传递给View层

在上一张图

public class UserPresenter implements UserCallback {
    private UserView  mUserView;
    private UserModel mModel;

    public UserPresenter(UserView baseView) {
        mUserView = baseView;
        mModel= new UserModel(this);
    }

    public void userLogin(String name, String pass){
        mUserView.onLogin();
        mModel.userLogin(name,pass);
    }

    @Override
    public void onSuccess(UserBean bean) {
        mUserView.loginSuccess(bean);
    }

    @Override
    public void onFail(Exception e, int code) {
        mUserView.loginFail(e,code);

    }
}

public  interface  UserCallback {
    void onSuccess(UserBean bean);
    void onFail(Exception e ,int code);
}

3.model层代码

model层进行网络请求等耗时任务处理,model会留有一个回调地址,当数据处理完成之后回调它,在本实例中UserCallback就是一个回调接口,具体实现类在Presenter层,也就是说数据处理完成之后会传递给Presenter层

public class UserModel {
    private UserCallback mUserCallback;
    private Map<String,String> mUserMaps;
    private Handler mHandler;

    /**
     * 
     * @param userCallback 回调地址,当数据处理完成之后调用这个接口
     */
    public UserModel(UserCallback userCallback) {
        mUserCallback = userCallback;
        mUserMaps=new HashMap<>();
        mHandler =new Handler(Looper.getMainLooper());
        mUserMaps.put("user1","123456");
        mUserMaps.put("user2","12345");
        mUserMaps.put("user3","1234");

    }

    public void userLogin(final  String name, final String pass){
        /**
         * 模拟延时操作,2秒后调用UserCallback接口,回传数据
         */
       mHandler.postDelayed(new Runnable() {
           @Override
           public void run() {
               if (mUserMaps.containsKey(name) && mUserMaps.get(name).equals(pass)){
                   UserBean bean =new UserBean(name,pass,20);
                   mUserCallback.onSuccess(bean);
               }else {
                   Exception exception =new Exception("用户名或账号错误");
                   mUserCallback.onFail(exception,400);
               }
           }
       },2000);
    }

}

4.MainActivity

public class MainActivity extends AppCompatActivity implements UserView ,View.OnClickListener {
    private  ProgressDialog mProgressDialog;
    private EditText mUserText;
    private EditText mUserPass;
    private Button mLoginBtn;
    private UserPresenter mUserPresenter;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mUserPresenter=new UserPresenter(this);
        initView();
        initEvents();
    }

    private void initEvents() {
        mLoginBtn.setOnClickListener(this);
    }

    public void initView () {
        mUserText = (EditText) findViewById(R.id.userName);
        mUserPass = (EditText) findViewById(R.id.userPass);
        mLoginBtn = (Button) findViewById(R.id.loginBtn);
    }

    @Override
    public void onLogin() {
        mProgressDialog =new ProgressDialog(this);
        mProgressDialog.show();