Appearance mode of design mode

Appearance Mode

definition

Facade mode is also known as facade mode.
It provides a consistent interface for a set of interfaces in a subsystem, defining a high-level interface that makes the subsystem easier to use.

Features

1. Facade mode requires that the communication between the internal and external subsystems must be carried out through the unified interface object
2. Facade pattern provides a high-level interface that makes subsystems easier to use

Application example of appearance mode

Appearance mode may sound a little unfamiliar, but we often see it
- examples in life
Initially , we need an mp3 to listen to music, an mp4 to watch movies, and a game console to play games. . . Now we can solve these needs with a single computer.
Here, mp3, mp4 and game console are a complete sub-function system in the computer, and the computer is the appearance of the whole system
- development examples
ImageLoder, XUtils, Volley, etc. all use appearance patterns
such as XUitls framework: many modules
For example: Load UI modules, download file modules, network request modules, etc...

Roles in Appearance Mode

1. The system provides a unified interface to the outside world
2. Subsystem interface

Design and Implementation of Appearance Mode

Example scenario: We design a computer with the functions of listening to music and playing games
Design subsystem:
1) Listen to music, provide an interface for the music listening subsystem, and implement

//接口
ublic interface IMusicServer {

    void start();

    void running(String musicName);

    void stop();

}

//具体类实现
public class MusicServerImpl implements IMusicServer {

    @Override
    public void start() {
        Log.i("main", "开始听音乐");
    }

    @Override
    public void running(String musicName) {
        Log.i("main", "听《" + musicName + "》歌曲");
    }

    @Override
    public void stop() {
        Log.i("main", "停止听音乐");
    }

}

2) Play games, provide game subsystem interfaces and implement them

接口

public interface IGameServer {

    void start();

    void running();

    void stop();

}

实现
public class GameServerImpl implements IGameServer {

    @Override
    public void start() {
        Log.i("main", "开始游戏");
    }

    @Override
    public void running() {
        Log.i("main", "运行游戏");
    }

    @Override
    public void stop() {
        Log.i("main", "停止游戏");
    }
}

Overall system design and implementation: (provide an overall unified interface for clients)

public class Computer {

    //外观模式重要特点：持有子系统引用(高层次接口)
    private IGameServer gameServer = new GameServerImpl();
    private IMusicServer musicServer = new MusicServerImpl();

    public void startGame(){
        gameServer.start();
        gameServer.running();
    }

    public void stopGame(){
        gameServer.stop();
    }

    public void startMusic(String musicName){
        musicServer.start();
        musicServer.running(musicName);
    }

    public void stopMusic(){
        musicServer.stop();
    }

}

使用：
    Computer computer = new Computer();
    computer.startGame();
    computer.stopGame();
    computer.startMusic("阳光总在风雨后");
    computer.stopMusic();
从使用上我们能看出，用户不需要关心子系统做了什么，只需要在整体系统中直接执行需要的命令即可，具体实现由子系统实现