Android的MVP模式讲解

你的名字 2023-10-17 15:18 83阅读 0赞

**UI层越来越复杂，为了减轻了UI层的责任，也是为了更好地细分视图(View)与模型(Model)的功能，让View专注于处理数 据的可视化以及与用户的交互，让Model只关系数据的处理，MVP(Model-View-Presenter)模式应运而生。每个人对MVP模式都有一定的理解，此篇仅供参考交流。**

**(1)View:负责绘制UI元素、与用户进行交互(View interface与Presenter进行交互，降低耦合);**  
**(2)Model:依然是业务逻辑和实体模型、操纵数据(有时也实现一个Model interface用来降低耦合);  
(3)Presenter:作为View与Model交互的中间纽带，负责完成View于Model间的交互（处理与用户交互的负责逻辑）**

**项目Demo结构图：**

![Center][]

**(1)首先我们需要一个Bean**

public class LoginUserBean {
    	 private String username;
    	 private String password;
    
    	    public String getUsername() {
    	        return username;
    	    }
    
    	    public void setUsername(String username) {
    	        this.username = username;
    	    }
    
    	    public String getPassword() {
    	        return password;
    	    }
    
    	    public void setPassword(String password) {
    	        this.password = password;
    	    }
    }

**(2)View的接口，需要用到的方法：**

public interface LoginView {
         void clearUsername();
    	 
         void clearPassword();
    	 
         void setUsernameError();
    
         void setPasswordError();
    
         void navigateToHome();
    }

**（3）LoginActivity实现View接口**

public class LoginActivity extends Activity implements LoginView,OnClickListener {
    
        private ProgressBar progressBar;
        private EditText username;
        private EditText password;
        private Button btn_login;
        private LoginPresenter presenter;
    
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
             
            initView();
            
        }
    
        private void initView() {
        	progressBar = (ProgressBar) findViewById(R.id.progress);
            username = (EditText) findViewById(R.id.username);
            password = (EditText) findViewById(R.id.password);
            btn_login=(Button) findViewById(R.id.button);
    
            btn_login.setOnClickListener(this);
            presenter = new LoginPresenterImpl(this);
    		
    	}
        @Override
        public void onClick(View v) {
            presenter.validateCredentials(username.getText().toString(), password.getText().toString());
        }
        
        @Override
        public void navigateToHome() {
        	//登录成功，跳转主页
        	//Intent intent=new Intent(this,MainActivity.class);
        	//startActivity(intent);
            Toast.makeText(this,"成功，跳转",Toast.LENGTH_SHORT).show();
        }
        
    
    
    
    	@Override
    	public void clearUsername() {
    		username.setText("");
    		
    	}
    
    	@Override
    	public void clearPassword() {
    		password.setText("");
    		
    	}
    
    
        @Override
        public void setUsernameError() {
            username.setError(getString(R.string.username_error));
        }
    
        @Override
        public void setPasswordError() {
            password.setError(getString(R.string.password_error));
        }
    
    
    
    	@Override
        protected void onDestroy() {
            presenter.onDestroy();
            super.onDestroy();
        }
    
    }

**（4）Model接口：**

public interface LoginModel {
        void login(String username, String password, OnLoginFinishedListener listener);
    }

**（5）Model接口的实现类:**

public class LoginModelImpl implements LoginModel{
    
    	@Override
        public void login(final String username, final String password, final OnLoginFinishedListener listener) {
    
            new Handler().postDelayed(new Runnable() {
            	//模拟耗时登录
                @Override 
                public void run() {
                     //此处判断用户密码
                    if (TextUtils.isEmpty(username)){
                        listener.onUsernameError();//model层里面回调listener
                    
                    }
                    if (TextUtils.isEmpty(password)){
                        listener.onPasswordError();
                     
                    }
                   //此处成功,(真实应该网络返回成功,这里省略)
                   //调用回调方法，通过LoginPresenter操作ui层,跳转到主页
                  listener.onSuccess();
                    
                }
            }, 2000);
        }
    
    }

**(6)Presenter桥梁接口:**

public interface LoginPresenter {
        void validateCredentials(String username, String password);
    
        void onDestroy();
    }

**(7)Presenter现实类，实现回调OnLoginFinishedListener，M层通过回调方法操作Ui层:**

public class LoginPresenterImpl implements LoginPresenter, OnLoginFinishedListener {
        private LoginView loginView;
        private LoginModel loginModel;
    
        public LoginPresenterImpl(LoginView loginView) {
            this.loginView = loginView;
            this.loginModel = new LoginModelImpl();
        }
        //ui层调用
        @Override
        public void validateCredentials(String username, String password) {
            loginModel.login(username, password, this);
        }
        @Override
        public void onSuccess() {
            if (loginView != null) {
            	//M层回调后，这里操作Ui层接口的跳转
                loginView.navigateToHome();
            }
        }
        @Override
        public void onDestroy() {
            loginView = null;
        }
    
        @Override
        public void onUsernameError() {
            if (loginView != null) {
                loginView.setUsernameError();
                loginView.clearUsername();
            }
        }
    
        @Override
        public void onPasswordError() {
            if (loginView != null) {
                loginView.setPasswordError();
                loginView.clearPassword();
            }
        }
    
    	@Override
    	public void clearUsername() {
    		// TODO Auto-generated method stub
    		
    	}
    
    	@Override
    	public void clearPassword() {
    		// TODO Auto-generated method stub
    		
    	}
    }

**（8）回调接口：**

public interface  OnLoginFinishedListener {
    	
              void clearUsername();
    	 
    	  void clearPassword();
    	 
    	  void onUsernameError();
    
    	  void onPasswordError();
    
    	  void onSuccess();
    }

**登录流程解析:**

**1-首先是点击了按钮，在Ui层LoginActivity调用桥梁实现类LoginPresenterImpl的方法validateCredentials（）**

@Override
        public void onClick(View v) {
            presenter.validateCredentials(username.getText().toString(), password.getText().toString());
        }

**2-LoginPresenterImpl类操作M层**

@Override
        public void validateCredentials(String username, String password) {
            loginModel.login(username, password, this);
        }

**3-LoginModelImpl中的login，当后台数据返回成功时，调用回调方法操作LoginPresenterImpl类onSuccess方法，  
这里onSuccess方法中loginView.navigateToHome()就是操作UI层，达到跳转主页.**

@Override
        public void login(final String username, final String password, final OnLoginFinishedListener listener) {
    
            new Handler().postDelayed(new Runnable() {
            	//模拟耗时登录
                @Override 
                public void run() {
                     //此处判断用户密码
                    if (TextUtils.isEmpty(username)){
                        listener.onUsernameError();//model层里面回调listener
                    
                    }
                    if (TextUtils.isEmpty(password)){
                        listener.onPasswordError();
                     
                    }
                   //此处成功,(真实应该网络返回成功,这里省略)
                   //调用回调方法，通过LoginPresenter操作ui层,跳转到主页
                  listener.onSuccess();
                    
                }
            }, 2000);
        }

**4-loginView.navigateToHome()方法操作的UI层如下:**

@Override
        public void navigateToHome() {
        	//登录成功，跳转主页
        	//Intent intent=new Intent(this,MainActivity.class);
        	//startActivity(intent);
            Toast.makeText(this,"成功，跳转",Toast.LENGTH_SHORT).show();
        }

**总结：通过上面流程可以看出，View只负责处理与用户进行交互，并把数据相关的逻辑操作都扔给了Presenter去做。而Presenter调用Model处理完数据之后，再通过IUserView更新View显示的信息。每个人对MVP模式都有一定的理解，此篇仅供参考交流。**

[Center]: https://img-blog.csdn.net/20170822160017531?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvbGluODU3/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/Center