获取文件资源的静态方法

Question

更新： 我希望媒体播放器是静态的，但如果我制作是静态的，它不起作用。 请注意，我想媒体播放静态的原因是，我想从其他类访问它（行注释）。 这是我的代码：

import javafx.application.Application; 
import javafx.beans.value.ChangeListener; 
import javafx.beans.value.ObservableValue; 
import javafx.event.ActionEvent; 
import javafx.event.EventHandler; 
import javafx.geometry.Pos; 
import javafx.scene.Group; 
import javafx.scene.Scene; 
import javafx.scene.control.*; 
import javafx.scene.layout.HBox; 
import javafx.scene.layout.VBox; 
import javafx.scene.media.Media; 
import javafx.scene.media.MediaPlayer; 
import javafx.scene.text.Font; 
import javafx.stage.Stage; 

import java.net.URL; 

public class Main extends Application { 
    static boolean isSoundOn = false; 
    static double soundVolume = .5; 
    MediaPlayer mediaPlayer = new MediaPlayer(new Media(Main.class.getResource("song.mp3").toString())); 

public static void main(String[] args) { 
    Application.launch(args); 
} 

@Override 
public void start(Stage primaryStage) { 
    mediaPlayer.play(); 
    primaryStage.setTitle("duet by what"); 

//  primaryStage.setFullScreen(true); 


    //Group gamePaused = new Group(); 
    //Scene _gamePaused = new Scene(gamePaused, 1200, 700); 
    //Group gameOver = new Group(); 
    //Scene _gameOver = new Scene(gameOver, 1200, 700); 
    //Group game = new Group(); 
    //Scene _game = new Scene(game, 1200, 700); 

    GUI gui = new GUI(); 
    primaryStage.setScene(gui.getMainMenu().getScene()); 
    primaryStage.show(); 
} 
} 

class GUI { 
    private MainMenu mainMenu = new MainMenu(); 



public class MainMenu { 
     private Scene scene; 

     private MainMenu() { 
      VBox vBox = new VBox(); 
      scene = new Scene(vBox, 400, 500); 
      scene.getStylesheets().add("stylesheet.css"); 

      Label info = new Label(
        "welcome the the what version\n" + 
          "of the well known Duet game!\n\n" + 
          "press \"I wanna play!\" to begin the game.\n\n" + 
          "please note that you can change\n" + 
          "the sound settings."); 
      info.setId("info"); 
      vBox.getChildren().add(info); 

      Button startGame = new Button("i wanna play right now!"); 
      startGame.setOnAction(new EventHandler<ActionEvent>() { 
       @Override 
       public void handle(ActionEvent event) { 
        System.out.println("game started!"); 
       } 
      }); 
      vBox.getChildren().add(startGame); 

      Label highScore = new Label("__highScore should be added here__"); 
      highScore.setId("highScore"); 
      vBox.getChildren().add(highScore); 

      Button quitGame = new Button("get me out of this game!"); 
      quitGame.setOnAction(new EventHandler<ActionEvent>() { 
       @Override 
       public void handle(ActionEvent event) { 
        System.out.println("game quitted!"); 
       } 
      }); 
      vBox.getChildren().add(quitGame); 

      CheckBox soundOn = new CheckBox("soundOn?"); 
      Tooltip tooltip = new Tooltip("if this box is checked, music will be played!"); 
      tooltip.setFont(new Font("Arial", 16)); 
      soundOn.setTooltip(tooltip); 
      soundOn.selectedProperty().addListener(new ChangeListener<Boolean>() { 
       public void changed(ObservableValue<? extends Boolean> ov, 
            Boolean old_val, Boolean new_val) { 
        Main.isSoundOn = soundOn.isSelected(); 
        System.out.println(Main.isSoundOn); 
       } 
      }); 
      vBox.getChildren().add(soundOn); 

      HBox changeVolumeWrapper = new HBox(); 
      changeVolumeWrapper.setId("hBox"); 
      Label sliderLabel = new Label("sound volume: "); 
      changeVolumeWrapper.getChildren().add(sliderLabel); 

      Slider soundVolume = new Slider(0, 1, .5); 
      soundVolume.valueProperty().addListener(new ChangeListener<Number>() { 
       public void changed(ObservableValue<? extends Number> ov, 
            Number old_val, Number new_val) { 
        Main.soundVolume = new_val.doubleValue(); 
        //Main.mediaPlayer.setVolume(Main.soundVolume); here is why i need media player static. 
        System.out.printf("%.2f\n", Main.soundVolume); 
       } 
      }); 
      changeVolumeWrapper.getChildren().add(soundVolume); 
      vBox.getChildren().add(changeVolumeWrapper); 
     } 

     public Scene getScene() { 
      return scene; 
     } 
    } 

    public MainMenu getMainMenu() { 
     return mainMenu; 
    } 
} 

任何其他修复我的代码可以理解的。 顺便说一句，这些都是错误的，我得到：

异常在线程“线程0” java.lang.IllegalStateException： 工具包在 com.sun.javafx.application.PlatformImpl.runLater未初始化（ PlatformImpl.java:273） 在 com.sun.javafx.application.PlatformImpl.runLater（PlatformImpl.java:268） 在javafx.application.Platform.runLater（Platform.java:83）在 javafx.scene.media .Media $ _MetadataListener.onMetadata（Media.java:541） at com.sun.media.jfxmediaimpl.MetadataParserImpl.done（MetadataParserImpl.java:120） at com.sun.media.jfxmediaimpl.platform.java.ID3MetadataParser.parse（ID3MetadataParser.java:237） 在 com.sun.media.jfxmediaimpl.MetadataParserImpl.run（MetadataParserImpl.java:103） 异常在线程“主“java.lang.ExceptionInInitializerError at java.lang.Class.forName0（Native Method）at java.lang.Class.forName（Class.java:264）at com.intellij.rt.execution.application.AppMain.main （AppMain.java:122） 引起：java.lang.IllegalStateException：工具包不 com.sun.javafx.application.PlatformImpl.runLater（PlatformImpl.java:273） 在 com.sun.javafx初始化 。 application.PlatformImpl.runLater（PlatformImpl.java:268） at javafx.application.Platform.runLater（Platform.java:83）at javafx.scene.media.MediaPlayer.init（MediaPlayer.java:515）at javafx.scene.media.MediaPlayer。（MediaPlayer.java:414 。）在 主（Main.java:22）... 3更

Answer 1

而不

为上下文对象调用getClass()被解释为与任何其他实例方法：this.getClass()。

在静态上下文中，可以使用ClassName.class引用该类;即你可以做

static URL resource = Main.class.getResource("a.mp3"); 

但是，在这种情况下，为什么你会希望这些变量是静态的;每个JVM实例只能创建一个Application子类的一个实例，而这些实例本身就是该实例的属性。

在您的（更新）问题的具体示例中，我将定义一个单独的类，封装MediaPlayer以及您当前使其为静态的其他属性。请注意，MediaPlayer本身定义了volume属性和muted属性。所以，你可以这样做：

public class SoundPlayer { 

    private final MediaPlayer mediaPlayer ; 

    public SoundPlayer(URL url) { 
     this.mediaPlayer = new MediaPlayer(new Media(url)); 
    } 

    public void play() { 
     mediaPlayer.play(); 
    } 

    public double getVolume() { 
     return mediaPlayer.getVolume(); 
    } 

    public void setVolume(double volume) { 
     mediaPlayer.setVolume(volume); 
    } 

    public boolean isSoundOn() { 
     return ! mediaPlayer.isMuted(); 
    } 

    public void setSoundOn(boolean soundOn) { 
     mediaPlayer.setMuted(! soundOn); 
    } 
} 

现在你Main类可以是：

public class Main extends Application { 

    public static void main(String[] args) { 
     Application.launch(args); 
    } 

    @Override 
    public void start(Stage primaryStage) { 

     SoundPlayer soundPlayer = new SoundPlayer(getClass().getResource("song.mp3")); 
     soundPlayer.play(); 


     primaryStage.setTitle("duet by Aran Mohyeddin"); 

     GUI gui = new GUI(soundPlayer); 

     primaryStage.setScene(gui.getMainMenu().getScene()); 
     primaryStage.show(); 
    } 

} 

并更新GUI和MainMenu类到对SoundPlayer参考：

public class MainMenu { 
     private Scene scene; 

     private final SoundPlayer soundPlayer ; 

     private MainMenu(SoundPlayer soundPlayer) { 

      this.soundPlayer = soundPlayer ; 

      // existing code omitted... 

      CheckBox soundOn = new CheckBox("soundOn?"); 
      Tooltip tooltip = new Tooltip("if this box is checked, music will be played!"); 
      tooltip.setFont(new Font("Arial", 16)); 
      soundOn.setTooltip(tooltip); 
      soundOn.selectedProperty().addListener(new ChangeListener<Boolean>() { 
       public void changed(ObservableValue<? extends Boolean> ov, 
            Boolean old_val, Boolean new_val) { 

        soundPlayer.setSoundOn(new_val); 
       } 
      }); 

      // ... 


      Slider soundVolume = new Slider(0, 1, .5); 
      soundVolume.valueProperty().addListener(new ChangeListener<Number>() { 
       public void changed(ObservableValue<? extends Number> ov, 
            Number old_val, Number new_val) { 

        soundPlayer.setVolumn(new_val.doubleValue()); 
        System.out.printf("%.2f\n", Main.soundVolume); 
       } 
      }); 
      changeVolumeWrapper.getChildren().add(soundVolume); 
      vBox.getChildren().add(changeVolumeWrapper); 
     } 

     public Scene getScene() { 
      return scene; 
     } 
    } 

    public MainMenu getMainMenu() { 
     return mainMenu; 
    } 
} 

还要注意如果你公开SoundPlayer的实际属性对象，例如：

public class SoundPlayer { 

    private final MediaPlayer mediaPlayer ; 

    // ... 


    public DoubleProperty volumeProperty() { 
     return mediaPlayer.volumeProperty(); 
    } 

    // ... 
} 

那么你可以简化你的一些代码：

Slider soundVolume = new Slider(0, 1, .5); 
    // instead of the listener, just do: 
    soundPlayer.volumeProperty().bindBidirectional(soundVolume.valueProperty()); 

（转换的mutedProperty到soundOnProperty是有点不太优雅。）