java背景和按钮问题

Question

运行此代码时遇到问题：

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.image.Image;
import javafx.scene.image.ImageView;
import javafx.scene.layout.HBox;
import javafx.stage.Stage;
import javafx.scene.control.Label;
import javafx.scene.control.Button;
import javafx.scene.paint.Color;
import javafx.scene.shape.Circle;
import javafx.scene.text.Font;
import javafx.scene.text.Text;
import javafx.scene.Group;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.BackgroundSize;
import javafx.scene.layout.Background;
import javafx.scene.layout.BackgroundImage;
import javafx.scene.layout.BackgroundRepeat;
import javafx.scene.layout.BackgroundPosition;
import javafx.event.ActionEvent;

import java.io.FileInputStream;

public class Main extends Application  {

@Override
public void start(Stage primaryStage) throws Exception {
    BackgroundImage backgroundImage = new BackgroundImage( new Image( getClass().getResource("src/sample/Image/backg.jpg").toExternalForm()), BackgroundRepeat.NO_REPEAT, BackgroundRepeat.NO_REPEAT, BackgroundPosition.DEFAULT, BackgroundSize.DEFAULT);
    Background background = new Background(backgroundImage);

    Button button = new Button( "Click me!");
    button.setBackground(background);

    Scene scene = new Scene(backgroundImage, 600, 400);

    primaryStage.setScene(scene);
    primaryStage.show();
}



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

我试图在后台显示按钮，但尽管如此，我还是面临很多问题。我真的不太明白“场景”课程是如何运作的，所以我觉得我犯了一个错误。 我收到以下错误消息：

Error:(38, 33) java: incompatible types: javafx.scene.layout.BackgroundImage cannot be converted to javafx.scene.Parent

38和33，即：

Background background = new Background(backgroundImage);
Scene scene = new Scene(backgroundImage, 600, 400);

谢谢

更新

在Matt回复后，我尝试了他的代码，得到了以下错误消息：

    Exception in Application start method
java.lang.reflect.InvocationTargetException
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:564)
at javafx.graphics/com.sun.javafx.application.LauncherImpl.launchApplicationWithArgs(LauncherImpl.java:473)
at javafx.graphics/com.sun.javafx.application.LauncherImpl.launchApplication(LauncherImpl.java:372)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:564)
at java.base/sun.launcher.LauncherHelper$FXHelper.main(LauncherHelper.java:941)
Caused by: java.lang.RuntimeException: Exception in Application start method
at javafx.graphics/com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java:973)
at javafx.graphics/com.sun.javafx.application.LauncherImpl.lambda$launchApplication$2(LauncherImpl.java:198)
at java.base/java.lang.Thread.run(Thread.java:844)
Caused by: java.lang.NullPointerException
at sample.Main.start(Main.java:34)
at javafx.graphics/com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$9(LauncherImpl.java:919)
at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runAndWait$11(PlatformImpl.java:449)
at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runLater$9(PlatformImpl.java:418)
at java.base/java.security.AccessController.doPrivileged(Native Method)
at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runLater$10(PlatformImpl.java:417)
at javafx.graphics/com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:96)
at javafx.graphics/com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at javafx.graphics/com.sun.glass.ui.win.WinApplication.lambda$runLoop$3(WinApplication.java:175)
... 1 more
Exception running application sample.Main

Process finished with exit code 1

Answer 1

希望下面的解释能对你有所帮助

backgroundImage不是父项，但按钮是，即button.setBackground(background);

因此，要显示带有背景的按钮，需要将按钮作为参数传递给场景构造函数：Scene scene = new Scene(button, 600, 400);。 如果你想在背景图像上显示按钮，那么你需要在某个窗格上设置按钮，并将你的图像放在窗格的背景上，这样你的目标就会有效地实现

Answer 2

在javafx中尝试一下，通常您希望将所有节点保存在一个容器中。看看我添加的评论

public class Main extends Application {

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

    @Override
    public void start(Stage primaryStage) {//Removed throws Exception
        BackgroundImage backgroundImage = new BackgroundImage( 
                new Image( getClass().getResource("src/sample/Image/backg.jpg").toExternalForm()),
                BackgroundRepeat.NO_REPEAT, 
                BackgroundRepeat.NO_REPEAT, 
                BackgroundPosition.DEFAULT, 
                BackgroundSize.DEFAULT);
        Background background = new Background(backgroundImage);

        Button button = new Button( "Click me!");
        //button.setBackground(background);Not needed

        VBox vBox = new VBox();//A container which holds all the nodes
        vBox.setBackground(background);//Set the Container Background
        vBox.getChildren().add(button);//Add Nodes

        Scene scene = new Scene(vBox, 600, 400);//Parameters are Parent and width and height of your scene

        primaryStage.setScene(scene);
        primaryStage.show();
    }
}