MVC
MVC ,早期的开发架构,在安卓里,用res代表V,activity代表Controller层,Model层完成数据请求,更新操作,activity完成view的绑定,以及业务逻辑的编写,更新view,这种模式是单向的,虽然代码存在分层,但是之间的耦合性还是很高,并且C层做的事情很多,久而久之会变得臃肿。
代码实现:
ViewModel
static class StudentModel{private String name;private int age;public StudentModel(String name, int age) {this.name = name;this.age = age;}public String getName() {return name;}public void setName(String name) {this.name = name;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}}
View层
static class StudentView{public void PrintStudentData(String name ,int age){System.out.println("Student name:"+name+" age:"+age);}}
Controller
static class StudentController{StudentModel model;StudentView view;public StudentController(StudentModel model, StudentView view) {this.model = model;this.view = view;}public void setStudentName(String name){model.setName(name);}public String getStudentName(){return model.getName();}public void setStudentAge(int age){model.setAge(age);}public Integer getStudentAge(){return model.getAge();}public void updateView(StudentView view){view.PrintStudentData(model.getName(),model.getAge());}}
完整代码
package com.example.lib;public class MvcTest {public static void main(String[] args) {StudentModel student = getStudentDataBase();StudentView view = new StudentView();StudentController controller = new StudentController(student,view);controller.updateView(view);controller.setStudentName("lisi");controller.updateView(view);}public static StudentModel getStudentDataBase(){return new StudentModel("zhangsan",18);}static class StudentModel{private String name;private int age;public StudentModel(String name, int age) {this.name = name;this.age = age;}public String getName() {return name;}public void setName(String name) {this.name = name;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}}static class StudentView{public void PrintStudentData(String name ,int age){System.out.println("Student name:"+name+" age:"+age);}}static class StudentController{StudentModel model;StudentView view;public StudentController(StudentModel model, StudentView view) {this.model = model;this.view = view;}public void setStudentName(String name){model.setName(name);}public String getStudentName(){return model.getName();}public void setStudentAge(int age){model.setAge(age);}public Integer getStudentAge(){return model.getAge();}public void updateView(StudentView view){view.PrintStudentData(model.getName(),model.getAge());}}}
MVP
于是,出现了MVP模式,这个架构模式在安卓移动端开发中比较常见,将Activity和res统一作为V层,Model层还是完成数据的请求和更新,新建了一个类Presenter,用来作为P层,这样的好处是,方便管理每一个Activity的业务逻辑,拿到数据后,通过接口回调的方式,更新View层,实现了双向通信。缺点是需要实现Presenter类,并且需要开发接口,对简单的业务逻辑比较繁琐,且P层的事情还是比较臃肿
代码实现(以登录事务为例):
ViewModel层
相比与MVC的ViewModel,MVP的不同在于ViewModle多实现了一个IUser接口,从而实现双向通信
interface IUser{void login(String name,String password,OnLoginListener listener);}interface OnLoginListener{void loginFail();void loginSuccess(User user);}static class UserModel implements IUser{@Overridepublic void login(String name, String password, OnLoginListener listener) {//模拟一下登录if(name.equals("admin")&&password.equals("123456")){User user = new User();user.setUsername(name);user.setPassword(password);listener.loginSuccess(user);}else{listener.loginFail();}}}
View层:
在Android开发中,MVP架构模式里,View层指的是Activity和res。同理,也实现了一个IUserLogin接口,从而和P层实现双向通信
static class UserView implements IUserLogin{@Overridepublic void showLoading() {System.out.println("正在登录...");}@Overridepublic void hideLoading() {System.out.println("登录完成,获取结果");}@Overridepublic void loginFail() {System.out.println("登录失败");}@Overridepublic void loginSuccess(User user) {System.out.println("username:"+ user.getUsername()+" 登陆成功");}}interface IUserLogin{void showLoading();void hideLoading();void loginFail();void loginSuccess(User user);}
Presenter层
static class UserPresenter {private final UserModel userModel;private final UserView userView;private final User user;public UserPresenter(UserView userView) {this.userModel = new UserModel();this.userView = userView;user = new User("admin","123456");}void login(){userView.showLoading();userModel.login(user.getUsername(), user.getPassword(), new OnLoginListener() {@Overridepublic void loginFail() {userView.hideLoading();userView.loginFail();}@Overridepublic void loginSuccess(User user) {userView.hideLoading();userView.loginSuccess(user);}});}}
完整代码如下:
package com.example.lib;public class MvpTest {public static void main(String[] args) {UserView loginView = new UserView();UserPresenter presenter = new UserPresenter(loginView);presenter.login();}static class User{String username;String password;public User() {}public User(String username, String password) {this.username = username;this.password = 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;}}interface IUser{void login(String name,String password,OnLoginListener listener);}interface OnLoginListener{void loginFail();void loginSuccess(User user);}static class UserModel implements IUser{@Overridepublic void login(String name, String password, OnLoginListener listener) {//模拟一下登录if(name.equals("admin")&&password.equals("123456")){User user = new User();user.setUsername(name);user.setPassword(password);listener.loginSuccess(user);}else{listener.loginFail();}}}static class UserView implements IUserLogin{@Overridepublic void showLoading() {System.out.println("正在登录...");}@Overridepublic void hideLoading() {System.out.println("登录完成,获取结果");}@Overridepublic void loginFail() {System.out.println("登录失败");}@Overridepublic void loginSuccess(User user) {System.out.println("username:"+ user.getUsername()+" 登陆成功");}}interface IUserLogin{void showLoading();void hideLoading();void loginFail();void loginSuccess(User user);}static class UserPresenter {private final UserModel userModel;private final UserView userView;private final User user;public UserPresenter(UserView userView) {this.userModel = new UserModel();this.userView = userView;user = new User("admin","123456");}void login(){userView.showLoading();userModel.login(user.getUsername(), user.getPassword(), new OnLoginListener() {@Overridepublic void loginFail() {userView.hideLoading();userView.loginFail();}@Overridepublic void loginSuccess(User user) {userView.hideLoading();userView.loginSuccess(user);}});}}}
MVVM
再后面,就是MVVM,同理,Activity和res还是作为V层,Model层请求数据和更新,出现了一个ViewModel的层,这个类的职责在于,对数据进行绑定,以数据驱动View层,同样,当视图层改变后,Model层也能更新,从而实现了M和V之间的双向绑定。最常用的是谷歌2015年推出的jetpack的组件DataBinding,无须进行view绑定,避免了空指针等很多繁琐的业务逻辑。
代码实现:略,用JetPack提供的databinding即可
总结
MVC,MVP,MVVM的出现,都是为了视图分层,使代码结构,逻辑变得清晰,同时,实现类的单一职责,降低耦合度。但是同时选用架构设计模式的时候,也要根据业务类型来考虑,避免出现大多繁琐的设计,总之,一切为了开发效率。