ComboBox无法强制转换为TextField？

Question

我有一个带有两个不同的控制下层（ComboBox，Textfield）的javafx.scene.control.Control（ArrayList）的ArrayList。

所以我想在两个文件中使用新的输入(example)更新列表。

但是当我尝试它时，eclipse会出现这样的错误：

Exception in thread "JavaFX Application Thread" java.lang.ClassCastException: javafx.scene.control.ComboBox cannot be cast to javafx.scene.control.TextField
    at application.DocumentBuildUp.aktualisiereListe(DocumentBuildUp.java:34)
    at application.MainStage$2.handle(MainStage.java:99)
    at application.MainStage$2.handle(MainStage.java:1)
    at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(Unknown Source)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(Unknown Source)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(Unknown Source)
    at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(Unknown Source)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Source)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Source)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Source)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Source)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Source)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Source)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Source)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Source)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Source)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Source)
    at com.sun.javafx.event.EventUtil.fireEventImpl(Unknown Source)
    at com.sun.javafx.event.EventUtil.fireEvent(Unknown Source)
    at javafx.event.Event.fireEvent(Unknown Source)
    at javafx.scene.Node.fireEvent(Unknown Source)
    at javafx.scene.control.Button.fire(Unknown Source)
    at com.sun.javafx.scene.control.behavior.ButtonBehavior.mouseReleased(Unknown Source)
    at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(Unknown Source)
    at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(Unknown Source)
    at com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(Unknown Source)
    at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(Unknown Source)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(Unknown Source)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(Unknown Source)
    at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(Unknown Source)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Source)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Source)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Source)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Source)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Source)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Source)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Source)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Source)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Source)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Source)
    at com.sun.javafx.event.EventUtil.fireEventImpl(Unknown Source)
    at com.sun.javafx.event.EventUtil.fireEvent(Unknown Source)
    at javafx.event.Event.fireEvent(Unknown Source)
    at javafx.scene.Scene$MouseHandler.process(Unknown Source)
    at javafx.scene.Scene$MouseHandler.access$1500(Unknown Source)
    at javafx.scene.Scene.impl_processMouseEvent(Unknown Source)
    at javafx.scene.Scene$ScenePeerListener.mouseEvent(Unknown Source)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(Unknown Source)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$354(Unknown Source)
    at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(Unknown Source)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(Unknown Source)
    at com.sun.glass.ui.View.handleMouseEvent(Unknown Source)
    at com.sun.glass.ui.View.notifyMouse(Unknown Source)
    at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at com.sun.glass.ui.win.WinApplication.lambda$null$148(Unknown Source)
    at java.lang.Thread.run(Unknown Source)

我希望你能提供帮助。

这是代码。 类DokumentBuilUp具有updateList的方法。我把它命名为＃34; aktualisiereListe＆＃34;。 ：））

Class MainStage：

public class MainStage extends Application {

    /**
     * Globale Variablen
     */
     private int abstandszaehler = 0;
     private ScrollPane rahmen = new ScrollPane();
     private XMLActions xA = new XMLActions();
     private Pane partPane = new Pane();
     private Group huelle = new Group();
     private int iD = 0;
     private List<Control> entries = new ArrayList<Control>();
     private DocumentBuildUp dBU = new DocumentBuildUp(entries);



     /**
     * The main class for a JavaFX application extends the javafx.application.Application class. 
     * The start() method is the main entry point for all JavaFX applications.
     */
    public static void main(String[] args) {
        launch(args);
    }


    @Override
    public void start(Stage primaryStage) {
        //Policy bezüglich Scrollingverhalten
        rahmen.setHbarPolicy(ScrollBarPolicy.ALWAYS);
        rahmen.setVbarPolicy(ScrollBarPolicy.ALWAYS);

        //Fenster konfigurieren und anzeigen
        primaryStage.setTitle("XML-Zeilenersteller");
        primaryStage.setResizable(false);


        //Erzeugt notwendige Elemente im GUI
         erzeugeEinzelneElemente();

        partPane.setStyle("-fx-background-color: lightsteelblue");
        huelle.getChildren().addAll(partPane);
        rahmen.setContent(huelle);
        Scene mainScene = new Scene(rahmen, 900, 590);
        primaryStage.setScene(mainScene);
        primaryStage.show();
    }







    /**
     * HauptElemente für die Root
     */
    public void erzeugeEinzelneElemente(){
        //Buttons
        Button newXMLLine = new Button();
        newXMLLine.setText("Einfügen neuer XML-Zeile");
        newXMLLine.setLayoutX(735);
        newXMLLine.setLayoutY(80);
        newXMLLine.setOnAction(new EventHandler<ActionEvent>() {
            @Override
            public void handle(ActionEvent event) {
                setEverythingInALine();
            }
        });

        Button newXMLDocument = new Button();
        newXMLDocument.setText("Erstelle XML-Dokument");
        newXMLDocument.setLayoutX(735);
        newXMLDocument.setLayoutY(550);
        newXMLDocument.setOnAction(new EventHandler<ActionEvent>() {
            @Override
            public void handle(ActionEvent event) {


                dBU.aktualisiereListe(entries);

                System.out.println("Test2");
            }
        });

        //Überschrift
        Text header = new Text(105, 50, "XML Lines Creator");
        header.setFont(new Font(30)); header.setStyle("-fx-underline: true;");

        /**
         * Hinzufügen zur GUI
         */
        partPane.getChildren().addAll(newXMLDocument,newXMLLine,header);
    }






    /**
     * Methode zur Erstellungen der Zeilen an Comboboxen, Textfelder
     */
    @SuppressWarnings({ "rawtypes", "unchecked" })
    public void setEverythingInALine(){
        //Comboboxen
        ComboBox cB = new ComboBox(xA.getList());   
        partPane.getChildren().add(cB);
        cB.setLayoutX(80);
        cB.setLayoutY(80 + abstandszaehler);
        entries.add(cB);
        iD++;
//        cB.setId(Integer.toString(iD));

        //Textfield
        TextField tFID= new TextField ("ID");
        partPane.getChildren().add(tFID);
        tFID.setLayoutX(185);
        tFID.setLayoutY(80 + abstandszaehler);
        entries.add(tFID);



        TextField tFName= new TextField ("Name");
        partPane.getChildren().add(tFName);
        tFName.setLayoutX(340);
        tFName.setLayoutY(80 + abstandszaehler);
        entries.add(tFName);


        TextField tFWert= new TextField ("Wert");
        partPane.getChildren().add(tFWert);
        tFWert.setLayoutX(495);
        tFWert.setLayoutY(80 + abstandszaehler);
        entries.add(tFWert);


        System.out.println(Integer.toString(iD));

        //Zaehler für den Abstand
        abstandszaehler = abstandszaehler + 30;

        System.out.println(entries);
    }
}

类DocumentBuilUp：

public class DocumentBuildUp{

    @SuppressWarnings("unused")
    private List<Control> list;

    public DocumentBuildUp(List<Control> list){
        this.list = list;
    }

    public List<String> aktualisiereListe(List<Control> list ){

        List<String> stringEntries = new ArrayList<String>();

        for(int i=0; i<=list.size()-1; i++){

            //Brauche die Zahl beim Anklicken der Zeile Listener?   
            if(i%3 == 1){
                ComboBox cB = (ComboBox) list.get(i);
                stringEntries.add((String) cB.getValue()); 
            }

            if(i%3 == 2 || i%3 == 0){
                TextField tF = (TextField) list.get(i);
                stringEntries.add(tF.getText());
            }
        }
        System.out.println(stringEntries);

        return stringEntries;
    }
}

编辑： 我可以用两个单独的列表来尝试它。一个用于Combobox，另一个用于Textfield。

编辑2： 它正与两位Arraylists合作！ ：））

Answer 1

如果您比较添加entries列表的内容以及如何在aktualisiereListe中使用它，您应该能够看到问题：

public void setEverythingInALine(){
    ...
    entries.add(someCombobox);
    ...
    entries.add(someTextfield);
    ...
    entries.add(someTextfield2);
    ...
    entries.add(someTextfield3);
}

这意味着有3 TextField s的子序列。第一个元素也是组合框

public List<String> aktualisiereListe(List<Control> list ){
    ...
    for(int i=0; i<=list.size()-1; i++){
        if(i%3 == 1){
            ComboBox cB = (ComboBox) list.get(i);
            ...
        }

        if(i%3 == 2 || i%3 == 0){
            TextField tF = (TextField) list.get(i);
            ...
        }
    }
    ...
}

这里假设第一个元素（索引0）为TextField（0 % 3 = 0），但并非如此。此外，3 TextField s的子序列将产生错误，因为3个连续索引将以模3的形式产生所有3个不同的值：

 1 % 3 = 1
 2 % 3 = 2
 3 % 3 = 0

哪会导致另一个ClassCastException。

我考虑在列表中添加元素并以这种方式检索它们是一种不好的做法，因为你不能改变元素的顺序（你可以，但是有非常严格的限制）而不会破坏其他元素aktualisiereListe。稍微好一点的方法是使用instanceof来检查元素类型：

    for(Control c : list) {
        if(c instanceof ComboBox){
            ComboBox cB = (ComboBox) c;
            ...
        } else {
            TextField tF = (TextField) c;
            ...
        }
    }

但是，您可以通过将更改侦听器注册到Control来保持一个始终保持最新的列表，这是我最喜欢的：

public class ListModifyingChangeListener implements ChangeListener<String> {
    private final int index;
    private final List<String> list;

    public ListModifyingChangeListener(int index, List<String> list) {
        this.index = index;
        this.list = list;
    }

    @Override
    public void changed(ObservableValue<? extends String> observable, String oldValue, String newValue) {
        list.set(index, newValue);
    }

}

    List<String> liste; // this could be declared a field

    ComboBox<String> cB = ...
    ...

    // create fixed sized list with initial values
    liste = Arrays.asList(cB.getValue(), tFID.getText(), tFName.getText(), tFWert.getText());

    // register listeners that modify a certain element of liste on change
    cB.valueProperty().addListener(new ListModifyingChangeListener(0, liste));
    tFID.textProperty().addListener(new ListModifyingChangeListener(1, liste));
    tFName.textProperty().addListener(new ListModifyingChangeListener(2, liste));
    tFWert.textProperty().addListener(new ListModifyingChangeListener(3, liste));

这可确保liste始终包含最新值，并且还可以防止不必要的列表重新创建。无需将控件列表传递给方法并区分控件类型......

Answer 2

ComboBox在（i％3 == 2 || i％3 == 0）的位置满足此条件，因此将ComboBox转换为TextField（（TextField）list.get（i））会面临错误。< / p>