適配器模式(Adapter Pattern)是作爲兩個不兼容的接口之間的橋樑。這種類型的設計模式屬於結構型模式,它結合了兩個獨立接口的功能。
這種模式涉及到一個單一的類,該類負責加入獨立的或不兼容的接口功能。舉個真實的例子,讀卡器是作爲內存卡和筆記本之間的適配器。您將內存卡插入讀卡器,再將讀卡器插入筆記本,這樣就可以通過筆記本來讀取內存卡。
我們通過下面的實例來演示適配器模式的使用。其中,音頻播放器設備只能播放 mp3 文件,通過使用一個更高級的音頻播放器來播放 vlc 和 mp4 文件。
適配器的創建步驟:
1.爲媒體播放器和更高級的媒體播放器創建接口
2.創建實現了 AdvancedMediaPlayer 接口的實體類
3.創建實現了 MediaPlayer 接口的適配器類
4.創建實現了 MediaPlayer 接口的實體類
5.使用 AudioPlayer 來播放不同類型的音頻格式
步驟一:
public interface MediaPlayer {
public void play(String audioType, String fileName);
}
public interface AdvancedMediaPlayer {
public void playVlc(String fileName);
public void playMp4(String fileName);
}
步驟二:
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) {
}
}
public class Mp4Player implements AdvancedMediaPlayer{
@Override
public void playVlc(String fileName) {
}
@Override
public void playMp4(String fileName) {
System.out.println("Playing mp4 file. Name: "+ fileName);
}
}
步驟三:
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);
}
}
}
步驟四:
public class AudioPlayer implements MediaPlayer {
MediaAdapter mediaAdapter;
@Override
public void play(String audioType, String fileName) {
//播放 mp3 音樂文件的內置支持
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");
}
}
}
步驟五:
public class AdapterPatternDemo {
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");
}
}