java - 应用程序构造函数 javafx 中的异常

Question

我的问题是关于 Java fx，我正在尝试制作一个媒体播放器。我尝试了这段代码，但它无法正常工作并且总是给出运行时错误。我怎样才能摆脱这个错误？

这是我的代码:

package mp4player;

import java.net.URL;
import javafx.application.Application;
import javafx.geometry.HPos;
import javafx.geometry.Insets;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.effect.DropShadow;
import javafx.scene.layout.GridPane;
import javafx.scene.layout.VBox;
import javafx.scene.media.Media;
import javafx.scene.media.MediaPlayer;
import javafx.scene.media.MediaView;
import javafx.scene.paint.Color;
import javafx.scene.shape.Rectangle;
import javafx.stage.Stage;
public class Mp4Player extends Application{

    public Mp4Player(Media media) {
    }
    public static void main(String[] args) {
        Application.launch(args);
    }

    @Override
    public void start(Stage stage) {
        // Locate the media content in the CLASSPATH
        URL mediaUrl = getClass().getResource("src/Video/TheProtector10.mp4");
        String mediaStringUrl = mediaUrl.toExternalForm();

        // Create a Media
        Media media = new Media(mediaStringUrl);

        // Create a Media Player
        final MediaPlayer player = new MediaPlayer(media);
        // Automatically begin the playback
        player.setAutoPlay(true);

        // Create a 400X300 MediaView
        MediaView mediaView = new MediaView(player);

        mediaView.setFitWidth(400);
        mediaView.setFitHeight(300);
        mediaView.setSmooth(true);
        mediaView.setLayoutX(200);
        mediaView.setLayoutY(200);
        // Create the DropShadow effect
        DropShadow dropshadow = new DropShadow();
        dropshadow.setOffsetY(5.0);
        dropshadow.setOffsetX(5.0);
        dropshadow.setColor(Color.RED);

        mediaView.setEffect(dropshadow);

        Rectangle rect4 = new Rectangle(35, 55, 95, 25);
        rect4.setFill(Color.RED);
        rect4.setStroke(Color.BLACK);
        rect4.setStrokeWidth(1);

        // Create the HBox
        // HBox controlBox = new HBox(5, null, null);

        // Create the VBox
        VBox root = new VBox(1, mediaView);

        GridPane gridpane = new GridPane();
        gridpane.setPadding(new Insets(95));
        gridpane.setHgap(1);
        gridpane.setVgap(10);

        GridPane.setHalignment(rect4, HPos.CENTER);

        Group grp = new Group();
        gridpane.add(root, 1, 1);

        grp.getChildren().add(gridpane);

        // Create the Scene
        Scene scene = new Scene(grp);

        // Add the scene to the Stage
        stage.setScene(scene);
        // Set the title of the Stage
        stage.setTitle("A simple Media Example");
        // Display the Stage
        stage.show();
    }

}

这是我运行此代码时总是遇到的错误。

run:
Exception in Application constructor
java.lang.reflect.InvocationTargetException
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at com.sun.javafx.application.LauncherImpl.launchApplicationWithArgs(LauncherImpl.java:389)
    at com.sun.javafx.application.LauncherImpl.launchApplication(LauncherImpl.java:328)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at sun.launcher.LauncherHelper$FXHelper.main(LauncherHelper.java:767)
Caused by: java.lang.RuntimeException: Unable to construct Application instance: class mp4player.Mp4Player
    at com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java:907)
    at com.sun.javafx.application.LauncherImpl.lambda$launchApplication$155(LauncherImpl.java:182)
    at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.NoSuchMethodException: mp4player.Mp4Player.<init>()
    at java.lang.Class.getConstructor0(Class.java:3082)
    at java.lang.Class.getConstructor(Class.java:1825)
    at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$161(LauncherImpl.java:818)
    at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$175(PlatformImpl.java:326)
    at com.sun.javafx.application.PlatformImpl.lambda$null$173(PlatformImpl.java:295)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.application.PlatformImpl.lambda$runLater$174(PlatformImpl.java:294)
    at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
    at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at com.sun.glass.ui.win.WinApplication.lambda$null$148(WinApplication.java:191)
    ... 1 more
Exception running application mp4player.Mp4Player
C:\Users\Lenovo\AppData\Local\NetBeans\Cache\8.2\executor-snippets\run.xml:53: Java returned: 1
**BUILD FAILED** (total time: 1 second)

Answer 1

只需删除不需要的构造函数即可:

//  public Mp4Player(Media media) {
//  }