私はプログラム（JAVA/FX）

Question

を再起動した後にイメージを選択することができます。私のプログラムは、私がイメージを選択したChoiceBoxを持っていて、それを自動的にImageViewを自動的に更新しますが、イメージをExeceptionと呼ばれる新しいイメージに変更したい しかし、私はプログラムを再起動するときに問題なく新しいイメージを選択できます。

mCb_img.getSelectionModel().selectedItemProperty().addListener(o -> { 

     mIv_img.setImage(new Image(getClass().getResource("/img/" + mCb_img.getSelectionModel().getSelectedItem()).toExternalForm())); 
    }); 

---

@FXML 
private void changeOnAction(ActionEvent event) { 
    File img = null; 
    Path source = null; 
    Path target = null; 

    imgfileChooser.setTitle("Open Image File"); 
    imgfileChooser.getExtensionFilters().add(
      new FileChooser.ExtensionFilter("JPG", "*.jpg")); 
    img = imgfileChooser.showOpenDialog(new Stage()); 
    source = img.toPath(); 
    if (img != null) { 
     try { 
      File saved = new File(System.getProperty("user.dir") + "/src/im" 
        + "g/" + source.getFileName()); 
      target = saved.toPath(); 
      Files.move(source, target); 
     } catch (IOException ex) { 
      System.out.println(ex.getMessage()); 
     } 
    } 

    mCb_img.getItems().add(source.getFileName().toString()); 
    // fillChoiceBox(); 

} 

---

private void fillChoiceBox() { 
    mCb_img.getItems().clear(); 
    try { 

     Files.walk(Paths.get(System.getProperty("user.dir") + "/src/img/")) 
       .forEach(filePath -> { 
        if (Files.isRegularFile(filePath)) { 
         mCb_img.getItems().add(filePath.getFileName() 
           .toString()); 
        } 
       }); 
    } catch (IOException ex) { 
     System.out.println("No files in IMG!"); 
    } 
    mCb_img.getSelectionModel().select(0); 
} 

---

Exception in thread "JavaFX Application Thread" java.lang.NullPointerException 
at zweitehu.FXMLDocumentController.lambda$setListeners$1(FXMLDocumentController.java:248) 
at zweitehu.FXMLDocumentController$$Lambda$219/404494396.invalidated(Unknown Source) 
at com.sun.javafx.binding.ExpressionHelper$Generic.fireValueChangedEvent(ExpressionHelper.java:349) 
at com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:81) 
at javafx.beans.property.ReadOnlyObjectWrapper$ReadOnlyPropertyImpl.fireValueChangedEvent(ReadOnlyObjectWrapper.java:176) 
at javafx.beans.property.ReadOnlyObjectWrapper.fireValueChangedEvent(ReadOnlyObjectWrapper.java:142) 
at javafx.beans.property.ObjectPropertyBase.markInvalid(ObjectPropertyBase.java:112) 
at javafx.beans.property.ObjectPropertyBase.set(ObjectPropertyBase.java:145) 
at javafx.scene.control.SelectionModel.setSelectedItem(SelectionModel.java:102) 
at javafx.scene.control.SingleSelectionModel.updateSelectedIndex(SingleSelectionModel.java:223) 
at javafx.scene.control.SingleSelectionModel.select(SingleSelectionModel.java:149) 
at javafx.scene.control.ChoiceBox$ChoiceBoxSelectionModel.select(ChoiceBox.java:402) 
at com.sun.javafx.scene.control.skin.ChoiceBoxSkin.lambda$addPopupItem$266(ChoiceBoxSkin.java:259) 
at com.sun.javafx.scene.control.skin.ChoiceBoxSkin$$Lambda$227/143169386.handle(Unknown Source) 
at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86) 
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238) 
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191) 
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58) 
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114) 
at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74) 
at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:49) 
at javafx.event.Event.fireEvent(Event.java:198) 
at javafx.scene.control.MenuItem.fire(MenuItem.java:462) 
at com.sun.javafx.scene.control.skin.ContextMenuContent$MenuItemContainer.doSelect(ContextMenuContent.java:1364) 
at com.sun.javafx.scene.control.skin.ContextMenuContent$MenuItemContainer.lambda$createChildren$324(ContextMenuContent.java:1317) 
at com.sun.javafx.scene.control.skin.ContextMenuContent$MenuItemContainer$$Lambda$231/1415399751.handle(Unknown Source) 
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:3724) 
at javafx.scene.Scene$MouseHandler.access$1500(Scene.java:3452) 
at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1728) 
at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2461) 
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:348) 
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:273) 
at java.security.AccessController.doPrivileged(Native Method) 
at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:382) 
at com.sun.glass.ui.View.handleMouseEvent(View.java:553) 
at com.sun.glass.ui.View.notifyMouse(View.java:925) 
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method) 
at com.sun.glass.ui.win.WinApplication.lambda$null$141(WinApplication.java:102) 
at com.sun.glass.ui.win.WinApplication$$Lambda$37/96639997.run(Unknown Source) 
at java.lang.Thread.run(Thread.java:745) 

Answer 1

あなたが再度アプリケーションをパッケージ化した後のファイルのみClass.getResourceを使用して利用できるようになりますを意味し、ソースディレクトリにファイルをコピーします（または、クラスパスまたはそれに相当するクラスにコピーしてください。あなたの設定）。

あなたがClass.getResourceを使用して取得する代わりにURLのファイルにURLを使用し、実行時に新しいイメージをアクセスする場合：

ImageView iv = new ImageView(); 

ComboBox<Path> comboBox = new ComboBox<>(); 
comboBox.setConverter(new StringConverter<Path>() { 

    @Override 
    public String toString(Path object) { 
     return object.getFileName().toString(); 
    } 

    @Override 
    public Path fromString(String string) { 
     throw new UnsupportedOperationException(); 
    } 

}); 

iv.imageProperty().bind(Bindings.createObjectBinding(() -> { 
    Path path = comboBox.getValue(); 

    // use url for the given path 
    return path == null ? null : new Image(path.toUri().toURL().toExternalForm()); 
}, comboBox.valueProperty())); 

をそしてComboBoxに項目タイプとしてパスを使用します。

Files.walk(Paths.get(System.getProperty("user.dir") + "/src/img/")) 
      .filter(Files::isRegularFile) 
      .forEach(comboBox.getItems()::add); 

また、ソースパス（changeOnAction）ではなく、ComboBoxにターゲットパスを追加します。

Files.move(source, target); 
comboBox.getItems().add(target);