06-ADAPTER

适配器模式 #

• 描述 #

  适配器模式（Adapter Pattern）是作为两个不兼容的接口之间的桥梁。这种类型的设计模式属于结构型模式，它结合了两个独立接口的功能。
  
  这种模式涉及到一个单一的类，该类负责加入独立的或不兼容的接口功能。举个真实的例子，读卡器是作为内存卡和笔记本之间的适配器。您将内存卡插入读卡器，再将读卡器插入笔记本，这样就可以通过笔记本来读取内存卡。
  
  我们通过下面的实例来演示适配器模式的使用。其中，音频播放器设备只能播放 mp3 文件，通过使用一个更高级的音频播放器来播放 vlc 和 mp4 文件。

• UML #

• 代码实现 #

  public class Main {
      public static void main(String[] args) {
  
          AudioPlayer audioPlayer = new AudioPlayer();
  
          audioPlayer.play("mp3", "beyond the horizon.mp3");
          audioPlayer.play("mp4", "alone.mp4");
          audioPlayer.play("vlc", "far far away.vlc");
          audioPlayer.play("avi", "mind me.avi");
      }
  }
  

  AudioPlayer.java

  public class AudioPlayer implements MediaPlayer {
      MediaAdapter mediaAdapter;
  
      @Override
      public void play(String audioType, String fileName) {
  
          //播放 mp3 音乐文件的内置支持
          if(audioType.equalsIgnoreCase("mp3")){
              System.out.println("Playing mp3 file. Name: "+ fileName);
          }
          //mediaAdapter 提供了播放其他文件格式的支持
          else if(audioType.equalsIgnoreCase("vlc")
                  || audioType.equalsIgnoreCase("mp4")){
              mediaAdapter = new MediaAdapter(audioType);
              mediaAdapter.play(audioType, fileName);
          }
          else{
              System.out.println("Invalid media. "+
                      audioType + " format not supported");
          }
      }
  }
  

  MediaPlayer.java

  public interface MediaPlayer {
      public void play(String audioType, String fileName);
  }
  

  MediaAdapter.java

  public class MediaAdapter implements MediaPlayer {
  
      AdvancedMediaPlayer advancedMusicPlayer;
  
      public MediaAdapter(String audioType){
          if(audioType.equalsIgnoreCase("vlc") ){
              advancedMusicPlayer = new VlcPlayer();
          } else if (audioType.equalsIgnoreCase("mp4")){
              advancedMusicPlayer = new Mp4Player();
          }
      }
  
      @Override
      public void play(String audioType, String fileName) {
          if(audioType.equalsIgnoreCase("vlc")){
              advancedMusicPlayer.playVlc(fileName);
          }else if(audioType.equalsIgnoreCase("mp4")){
              advancedMusicPlayer.playMp4(fileName);
          }
      }
  }
  

  Mp4Player.java

  public class Mp4Player implements AdvancedMediaPlayer{
  
      @Override
      public void playVlc(String fileName) {
          //什么也不做
      }
  
      @Override
      public void playMp4(String fileName) {
          System.out.println("Playing mp4 file. Name: "+ fileName);
      }
  }
  

  VlcPlayer.java

  public class VlcPlayer implements AdvancedMediaPlayer{
      @Override
      public void playVlc(String fileName) {
          System.out.println("Playing vlc file. Name: "+ fileName);
      }
  
      @Override
      public void playMp4(String fileName) {
          //什么也不做
      }
  }
  

  AdvancedMediaPlayer.java

  public interface AdvancedMediaPlayer {
      public void playVlc(String fileName);
      public void playMp4(String fileName);
  }
  

  

• Reference #

  • https://www.runoob.com/design-pattern/adapter-pattern.html