スクロールペインのコンテンツをjpgファイルとして保存する方法

Question

以下は私のコードです。ここではScrollPaneの内容をjpgファイルとして保存しようとしています。それは私にIllegalArgumentExceptionエラーを与えています。 Sofar私はthisとthisで試しましたが、明らかに私は間違った引数をImageIO.writeメソッドに入れています。私はここで何が欠けていますか？

ここ

package urd.View; 

    import java.awt.image.BufferedImage; 
    import java.io.File; 
    import java.io.IOException; 
    import java.util.logging.Level; 
    import java.util.logging.Logger; 
    import javafx.application.Application; 
    import static javafx.application.Application.launch; 
    import javafx.embed.swing.SwingFXUtils; 
    import javafx.event.ActionEvent; 
    import javafx.scene.Scene; 
    import javafx.scene.SnapshotParameters; 
    import javafx.scene.control.Menu; 
    import javafx.scene.control.MenuBar; 
    import javafx.scene.control.MenuItem; 
    import javafx.scene.control.ScrollPane; 
    import javafx.scene.image.WritableImage; 
    import javafx.scene.layout.BorderPane; 
    import javafx.scene.layout.Pane; 
    import javafx.scene.paint.Color; 
    import javafx.scene.shape.Circle; 
    import javafx.scene.shape.Rectangle; 
    import javafx.stage.Stage; 
    import javax.imageio.ImageIO; 
    import javax.swing.JFileChooser; 

    /** 
    * 
    * @author urd 
    */ 
    public class NewFXMain extends Application { 

private final int width = 250; 
private final int height = 250; 

private final int radius = 15; 
double circleX = width/2; 
double circleY = height/2; 
Circle circle = new Circle(circleX, circleY, radius); 

/** 
* @param args the command line arguments 
*/ 
public static void main(String[] args) { 
    launch(args); 
} 

/** 
* @param primaryStage the command line arguments 
*/ 
@Override 
public void start(Stage primaryStage) { 
    BorderPane rootPane = new BorderPane(); 
    ScrollPane scrollPane = new ScrollPane(); 
    MenuBar menuBar = new MenuBar(); 
    Menu fileMenu = new Menu("File"); 
    Menu generator = new Menu("generate"); 
    MenuItem generateItem = new MenuItem("generate"); 
    menuBar.getMenus().addAll(fileMenu, generator); 
    MenuItem saveItem = new MenuItem("Save Image"); 
    fileMenu.getItems().addAll(saveItem); 
    generator.getItems().addAll(generateItem); 
    rootPane.setTop(menuBar); 
    rootPane.setCenter(scrollPane); 
    Scene scene = new Scene(rootPane, 400, 350); 
    primaryStage.setTitle("Image Generator"); 
    primaryStage.setScene(scene); 
    primaryStage.show(); 
    saveItem.setOnAction((ActionEvent event) -> { 
     // the content of scrollPane is saved as a JPEG file. 
     WritableImage img = scrollPane.snapshot(new SnapshotParameters(), null); 
     JFileChooser chooser = new JFileChooser(); 
     chooser.setCurrentDirectory(new File(System.getProperty("user.home"))); 
     File fileToSave = chooser.getSelectedFile(); 
     BufferedImage img2 = SwingFXUtils.fromFXImage(img, null); 
     int result = chooser.showSaveDialog(null); 
     if (result == JFileChooser.APPROVE_OPTION) { 
      try { 
       ImageIO.write(img2, "png", fileToSave); 
      } catch (IOException ex) { 
       Logger.getLogger(GuiClass.class.getName()).log(Level.SEVERE, null, ex); 
      } 
     } 
    }); 
    generateItem.setOnAction((ActionEvent event) -> { 
     //Here we call the generateImage method which takes in two int values and returns a pane 
     scrollPane.setContent(generateImage()); 
    }); 
} 

private Pane generateImage() { 
    Rectangle rectCanvas = new Rectangle(width, 
     height); 
    rectCanvas.setFill(Color.GREEN); 
    circle.setFill(Color.RED); 
    Pane pane = new Pane(); 
    pane.getChildren().addAll(rectCanvas, circle); 
    return pane; 
} 

}

IllegalArgumentException

Exception in thread "JavaFX Application Thread" java.lang.IllegalArgumentException: output == null! 
at javax.imageio.ImageIO.write(ImageIO.java:1516) 
at urd.View.NewFXMain.lambda$start$0(NewFXMain.java:86) 
at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86) 
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238) 
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191) 
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58) 
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114) 
at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74) 
at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:49) 
at javafx.event.Event.fireEvent(Event.java:198) 
at javafx.scene.control.MenuItem.fire(MenuItem.java:462) 
at com.sun.javafx.scene.control.skin.ContextMenuContent$MenuItemContainer.doSelect(ContextMenuContent.java:1405) 
at com.sun.javafx.scene.control.skin.ContextMenuContent$MenuItemContainer.lambda$createChildren$343(ContextMenuContent.java:1358) 
at com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(CompositeEventHandler.java:218) 
at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:80) 
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238) 
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191) 
at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59) 
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58) 
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114) 
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56) 
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114) 
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56) 
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114) 
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56) 
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114) 
at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74) 
at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54) 
at javafx.event.Event.fireEvent(Event.java:198) 
at javafx.scene.Scene$MouseHandler.process(Scene.java:3757) 
at javafx.scene.Scene$MouseHandler.access$1500(Scene.java:3485) 
at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1762) 
at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2494) 
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:381) 
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:295) 
at java.security.AccessController.doPrivileged(Native Method) 
at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$354(GlassViewEventHandler.java:417) 
at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:389) 
at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:416) 
at com.sun.glass.ui.View.handleMouseEvent(View.java:555) 
at com.sun.glass.ui.View.notifyMouse(View.java:937) 
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method) 
at com.sun.glass.ui.win.WinApplication.lambda$null$148(WinApplication.java:191) 
at java.lang.Thread.run(Thread.java:745) 

Answer 1

chooser.getSelectedFile（のためのログですが）showSaveDialog（）呼び出しの後にFileオブジェクトを返し、そうshowSaveDialog（）メソッドの後にファイルオブジェクトを作成します以下の方法で電話してください。

saveItem.setOnAction((ActionEvent event) -> { 
       // the content of scrollPane is saved as a JPEG file. 
       WritableImage img = scrollPane.snapshot(new SnapshotParameters(), null); 
       JFileChooser chooser = new JFileChooser(); 
       chooser.setCurrentDirectory(new File(System.getProperty("user.home"))); 
       // File fileToSave = chooser.getSelectedFile();//Remove this line. 
       BufferedImage img2 = SwingFXUtils.fromFXImage(img, null); 
       int result = chooser.showSaveDialog(null); 
       if (result == JFileChooser.APPROVE_OPTION) { 
        try { 
         File fileToSave = chooser.getSelectedFile(); 
         ImageIO.write(img2, "png", fileToSave); 
        } catch (IOException ex) { 
         Logger.getLogger(GuiClass.class.getName()).log(Level.SEVERE, null, ex); 
        } 
       } 
      });