android架构模式之MVP

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What?

Model-View-Presenter

Why?

Activity太忙了！既作为View又作为Controller，还要忙着与Model耦合
Activity一般会采用布局文件来作为视图，但大多情况下还需要在Activity中对View进行动态布局、变化，所以我说Activity承担了View的工作
Activity显然也是一个Controller，当用户与视图交互，还是Activity来处理相关视图逻辑
Activity还需要调用Model来处理相关业务逻辑，与Model也是耦合的

How?

降低Activity的职责，将其仅作为一个View，不再与Model有任何耦合
抽出Presenter，Presenter通过接口访问View，包含Model的引用；View包含Presenter的引用，间接调用Model层处理业务逻辑，见下图
MVC VS. MVP

A Simple Example

整体包图见下图，分model、view、presenter三个包
package diagram
model下VO表示Value Object，其实就是java bean，仅包含get、set方法，BO表示Bussiness Object，处理业务逻辑，
那么BO中异步完成业务后如何通知View呢？就靠这个Callback接口，由Presenter中实现

model.BO.IUserModel

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public interface IUserModel {
    public void login(LoginRequest request, Callback<LoginResponse> callback);
}

model.BO.UserModel

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public class UserModel implements IUserModel{
    @Override
    public void login(final LoginRequest request, final Callback<LoginResponse> callback) {
        new Thread(new Runnable() {
            @Override
            public void run() {
                String userName = request.getUserName();
                String userPassword = request.getUserPassword();
                //此处进行网络请求验证用户邮箱、密码是否合法
                //..
                boolean isValid = userName.equals("admin") && userPassword.equals("123456");
                if(isValid){
                    //模拟从服务器获得的accessToken
                    callback.success(new LoginResponse("a7f7v9l0389f8k3ls9"));
                }else{
                    //模拟从服务器获得的错误原因
                    callback.fail("用户名或密码错误");
                }
            }
        }).start();
    }
}

model.VO.LoginRequest

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public class LoginRequest {
    private String userName;
    private String userPassword;
    public LoginRequest() {
    }
    public LoginRequest(String userPassword, String userName) {
        this.userPassword = userPassword;
        this.userName = userName;
    }
    public String getUserName() {
        return userName;
    }
    public void setUserName(String userName) {
        this.userName = userName;
    }
    public String getUserPassword() {
        return userPassword;
    }
    public void setUserPassword(String userPassword) {
        this.userPassword = userPassword;
    }
}

model.VO.LoginResponse

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public class LoginResponse {
    private String accessToken;
    public LoginResponse() {
    }
    public LoginResponse(String accessToken) {
        this.accessToken = accessToken;
    }
    public String getAccessToken() {
        return accessToken;
    }
    public void setAccessToken(String accessToken) {
        this.accessToken = accessToken;
    }
}

model.Callback

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public interface Callback<T> {
    void success(T t);
    void fail(String reason);
}

presenter.ILoginPresenter

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public interface ILoginPresenter{
    public void login();
}

presenter.LoginPresenter

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public class LoginPresenter implements ILoginPresenter {
    private ILoginView loginView;
    private IUserModel userModel;
    private Handler handler;
    public LoginPresenter(ILoginView loginView) {
        this.loginView = loginView;
        this.userModel = new UserModel();
        this.handler = new Handler(Looper.getMainLooper());
    }
    @Override
    public void login() {
        userModel.login(new LoginRequest(loginView.getUserName(), loginView.getUserPassword()), new Callback<LoginResponse>() {
            @Override
            public void success(LoginResponse loginResponse) {
                String accessToken = loginResponse.getAccessToken();
                //此处缓存accessToken或其他操作
                //..
                handler.post(new Runnable() {
                    @Override
                    public void run() {
                        loginView.loginSuccess();
                    }
                });
            }
            @Override
            public void fail(final String reason) {
                handler.post(new Runnable() {
                    @Override
                    public void run() {
                        loginView.loginFail(reason);
                    }
                });
            }
        });
    }
}

view.ILoginView

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public interface ILoginView {
    public String getUserName();
    public String getUserPassword();
    public void loginSuccess();
    public void loginFail(String reason);
}

view.LoginActivity

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public class LoginActivity extends AppCompatActivity implements ILoginView{
    private EditText userNameEditText;
    private EditText userPasswordEditText;
    private Button loginButton;
    private ILoginPresenter loginPresenter;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_login);
        loginPresenter = new LoginPresenter(this);
        userNameEditText = (EditText)findViewById(R.id.username);
        userPasswordEditText = (EditText)findViewById(R.id.password);
        loginButton = (Button)findViewById(R.id.login);
        loginButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                loginPresenter.login();
            }
        });
    }
    @Override
    public String getUserName() {
        return userNameEditText.getText().toString();
    }
    @Override
    public String getUserPassword() {
        return userPasswordEditText.getText().toString();
    }
    @Override
    public void loginSuccess() {
        Toast.makeText(this, "登录成功", Toast.LENGTH_SHORT).show();
        //跳转到其他Activity或进行其他操作
        //..
    }
    @Override
    public void loginFail(String reason) {
        Toast.makeText(this, reason, Toast.LENGTH_SHORT).show();
    }
}

是不是结构还挺清楚的呢？至于是否要在项目中采用MVP，其实还要看项目的规模
demo图如下
demo