Peter Penzov Peter Penzov - 6 months ago 46
Java Question

Cannot cast Object in JavaFX combobox

I have this combobox which is user to display data by ID and Name:

public class Listobject extends Application
{


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

@Override
public void start(Stage stage)
{

// Insert Some data

final ComboBox<ListGroupsObj> listGroups = new ComboBox();


listGroups.setButtonCell(new GroupListCell());
listGroups.setCellFactory(new Callback<ListView<ListGroupsObj>, ListCell<ListGroupsObj>>()
{
@Override
public ListCell<ListGroupsObj> call(ListView<ListGroupsObj> p)
{
return new GroupListCell();
}
});

listGroups.setEditable(true);

ListGroupsObj ob = ListGroupsObj.newInstance().groupId(12).groupName("Group12");
listGroups.getItems().addAll(ob);
ListGroupsObj osb = ListGroupsObj.newInstance().groupId(13).groupName("Group13");
listGroups.getItems().addAll(osb);
ListGroupsObj oa = ListGroupsObj.newInstance().groupId(14).groupName("Group14");
listGroups.getItems().addAll(oa);
ListGroupsObj oz = ListGroupsObj.newInstance().groupId(15).groupName("Group15");
listGroups.getItems().addAll(oz);


// second way to add object
listGroups.getItems().add(new ListGroupsObj(12, "Group 12"));

listGroups.setValue(ob);

// Display the selected Group
listGroups.getSelectionModel().selectedItemProperty().addListener(new ChangeListener<ListGroupsObj>()
{

@Override
public void changed(ObservableValue<? extends ListGroupsObj> arg0, ListGroupsObj arg1, ListGroupsObj arg2)
{
if (arg2 != null)
{
System.out.println("Selected Group: " + arg2.getGroupId() + " - " + arg2.getGroupName());
}
}
});

final StackPane layout = new StackPane();
layout.getChildren().add(listGroups);
layout.setStyle("-fx-background-color: cornsilk; -fx-padding: 15;");
stage.setScene(new Scene(layout));
stage.show();
}

class GroupListCell extends ListCell<ListGroupsObj>
{
@Override
protected void updateItem(ListGroupsObj item, boolean empty)
{
super.updateItem(item, empty);
if (item != null)
{
setText(item.getGroupId() + " - " + item.getGroupName());
}
}
}

private List<ListGroupsObj> lisGroups;

public static class ListGroupsObj
{

private int groupId;
private String groupName;

public static ListGroupsObj newInstance()
{
return new ListGroupsObj();
}

public ListGroupsObj()
{
}

public ListGroupsObj(int groupId, String groupName)
{
this.groupId = groupId;
this.groupName = groupName;
}

public ListGroupsObj groupId(int groupId)
{
this.groupId = groupId;
return this;
}

public ListGroupsObj groupName(String groupName)
{
this.groupName = groupName;
return this;
}

public int getGroupId()
{
return groupId;
}

public String getGroupName()
{
return groupName;
}

@Override
public String toString()
{
return groupId + " - " + groupName;
}
}
}


When I run the code I get this error:

Exception in thread "JavaFX Application Thread" java.lang.ClassCastException: java.lang.String cannot be cast to listobject.Listobject$ListGroupsObj
at listobject.Listobject$2.changed(Listobject.java:79)
at com.sun.javafx.binding.ExpressionHelper$Generic.fireValueChangedEvent(ExpressionHelper.java:347)
at com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:80)
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.ComboBox$2.changed(ComboBox.java:221)
at com.sun.javafx.binding.ExpressionHelper$Generic.fireValueChangedEvent(ExpressionHelper.java:347)
at com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:80)
at javafx.beans.property.ObjectPropertyBase.fireValueChangedEvent(ObjectPropertyBase.java:105)
at javafx.beans.property.ObjectPropertyBase.markInvalid(ObjectPropertyBase.java:112)
at javafx.beans.property.ObjectPropertyBase.set(ObjectPropertyBase.java:145)
at javafx.scene.control.ComboBoxBase.setValue(ComboBoxBase.java:167)
at com.sun.javafx.scene.control.skin.ComboBoxListViewSkin.setTextFromTextFieldIntoComboBoxValue(ComboBoxListViewSkin.java:511)
at com.sun.javafx.scene.control.skin.ComboBoxListViewSkin.access$200(ComboBoxListViewSkin.java:57)
at com.sun.javafx.scene.control.skin.ComboBoxListViewSkin$6.changed(ComboBoxListViewSkin.java:416)
at com.sun.javafx.scene.control.skin.ComboBoxListViewSkin$6.changed(ComboBoxListViewSkin.java:406)
at com.sun.javafx.binding.ExpressionHelper$Generic.fireValueChangedEvent(ExpressionHelper.java:347)
at com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:80)
at javafx.beans.property.ReadOnlyBooleanPropertyBase.fireValueChangedEvent(ReadOnlyBooleanPropertyBase.java:72)
at javafx.scene.Node$FocusedProperty.notifyListeners(Node.java:7486)
at javafx.scene.Node.setFocused(Node.java:7537)
at com.sun.javafx.scene.control.skin.ComboBoxListViewSkin$FakeFocusTextField.setFakeFocus(ComboBoxListViewSkin.java:696)
at com.sun.javafx.scene.control.skin.ComboBoxListViewSkin$2.changed(ComboBoxListViewSkin.java:145)
at com.sun.javafx.scene.control.skin.ComboBoxListViewSkin$2.changed(ComboBoxListViewSkin.java:141)
at com.sun.javafx.binding.ExpressionHelper$Generic.fireValueChangedEvent(ExpressionHelper.java:347)
at com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:80)
at javafx.beans.property.ReadOnlyBooleanPropertyBase.fireValueChangedEvent(ReadOnlyBooleanPropertyBase.java:72)
at javafx.scene.Node$FocusedProperty.notifyListeners(Node.java:7486)
at javafx.scene.Node.setFocused(Node.java:7537)
at javafx.scene.Scene$KeyHandler.setWindowFocused(Scene.java:3856)
at javafx.scene.Scene$KeyHandler$1.invalidated(Scene.java:3875)
at com.sun.javafx.binding.ExpressionHelper$SingleInvalidation.fireValueChangedEvent(ExpressionHelper.java:135)
at com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:80)
at javafx.beans.property.ReadOnlyBooleanWrapper$ReadOnlyPropertyImpl.fireValueChangedEvent(ReadOnlyBooleanWrapper.java:178)
at javafx.beans.property.ReadOnlyBooleanWrapper$ReadOnlyPropertyImpl.access$100(ReadOnlyBooleanWrapper.java:148)
at javafx.beans.property.ReadOnlyBooleanWrapper.fireValueChangedEvent(ReadOnlyBooleanWrapper.java:144)
at javafx.beans.property.BooleanPropertyBase.markInvalid(BooleanPropertyBase.java:110)
at javafx.beans.property.BooleanPropertyBase.set(BooleanPropertyBase.java:143)
at javafx.stage.Window.setFocused(Window.java:409)
at com.sun.javafx.stage.WindowPeerListener.changedFocused(WindowPeerListener.java:59)
at com.sun.javafx.tk.quantum.GlassWindowEventHandler.run(GlassWindowEventHandler.java:89)
at com.sun.javafx.tk.quantum.GlassWindowEventHandler.run(GlassWindowEventHandler.java:39)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.tk.quantum.GlassWindowEventHandler.handleWindowEvent(GlassWindowEventHandler.java:130)
at com.sun.glass.ui.Window.handleWindowEvent(Window.java:1235)
at com.sun.glass.ui.Window.notifyFocus(Window.java:1210)
at com.sun.glass.ui.win.WinWindow._setVisible(Native Method)
at com.sun.glass.ui.Window.setVisible(Window.java:570)
at com.sun.javafx.tk.quantum.WindowStage.setVisible(WindowStage.java:443)
at javafx.stage.Window$9.invalidated(Window.java:776)
at javafx.beans.property.BooleanPropertyBase.markInvalid(BooleanPropertyBase.java:109)
at javafx.beans.property.BooleanPropertyBase.set(BooleanPropertyBase.java:143)
at javafx.stage.Window.setShowing(Window.java:826)
at javafx.stage.Window.hide(Window.java:851)
at com.sun.javafx.stage.WindowCloseRequestHandler.dispatchBubblingEvent(WindowCloseRequestHandler.java:45)
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.EventUtil.fireEventImpl(EventUtil.java:74)
at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
at javafx.event.Event.fireEvent(Event.java:204)
at com.sun.javafx.stage.WindowPeerListener.closing(WindowPeerListener.java:80)
at com.sun.javafx.tk.quantum.GlassWindowEventHandler.run(GlassWindowEventHandler.java:113)
at com.sun.javafx.tk.quantum.GlassWindowEventHandler.run(GlassWindowEventHandler.java:39)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.tk.quantum.GlassWindowEventHandler.handleWindowEvent(GlassWindowEventHandler.java:130)
at com.sun.glass.ui.Window.handleWindowEvent(Window.java:1235)
at com.sun.glass.ui.Window.notifyClose(Window.java:1139)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.access$300(WinApplication.java:39)
at com.sun.glass.ui.win.WinApplication$4$1.run(WinApplication.java:112)
at java.lang.Thread.run(Thread.java:744)


This line is the problem:

listGroups.getSelectionModel().selectedItemProperty().addListener(new ChangeListener<ListGroupsObj>()
{

@Override
public void changed(ObservableValue<? extends ListGroupsObj> arg0, ListGroupsObj arg1, ListGroupsObj arg2)
{
if (arg2 != null)
{
System.out.println("Selected Group: " + arg2.getGroupId() + " - " + arg2.getGroupName());
}
}
});


Can you help me to fix this issue?

P.S I will add this converter:

public class GroupConverter extends StringConverter<ListGroupsObj>
{

@Override
public String toString(ListGroupsObj obj)
{
return obj.getGroupId() + " - " + obj.getGroupName();
}

@Override
public ListGroupsObj fromString(String obj)
{

//TODO when you type for example "45 - NextGroup" you want to take only tyhe number"
return ListGroupsObj.newInstance().groupName(obj);
}

}

Answer

Peter use this code

import javafx.application.Application;
import javafx.beans.value.ChangeListener;
import javafx.beans.value.ObservableValue;
import javafx.scene.Scene;
import javafx.scene.control.ComboBox;
import javafx.scene.control.ListCell;
import javafx.scene.control.ListView;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;
import javafx.util.Callback;

/**
 *
 * @author reegan
 */
public class Listobject extends Application {

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

    @Override
    public void start(Stage stage) {

        // Insert Some data

        final ComboBox<ListGroupsObj> listGroups = new ComboBox();


        listGroups.setButtonCell(new GroupListCell());
        listGroups.setCellFactory(new Callback<ListView<ListGroupsObj>, ListCell<ListGroupsObj>>() {
            @Override
            public ListCell<ListGroupsObj> call(ListView<ListGroupsObj> p) {
                return new GroupListCell();
            }
        });

        listGroups.setEditable(true);

        ListGroupsObj ob = ListGroupsObj.newInstance().groupId(12).groupName("Group12");
        listGroups.getItems().addAll(ob);
        ListGroupsObj osb = ListGroupsObj.newInstance().groupId(13).groupName("Group13");
        listGroups.getItems().addAll(osb);
        ListGroupsObj oa = ListGroupsObj.newInstance().groupId(14).groupName("Group14");
        listGroups.getItems().addAll(oa);
        ListGroupsObj oz = ListGroupsObj.newInstance().groupId(15).groupName("Group15");
        listGroups.getItems().addAll(oz);


        // second way to add object
        listGroups.getItems().add(new ListGroupsObj(12, "Group 12"));

        listGroups.setValue(ob);

        // Display the selected Group
//        listGroups.getSelectionModel().selectedItemProperty().addListener(new ChangeListener<ListGroupsObj>() {
//            @Override
//            public void changed(ObservableValue<? extends ListGroupsObj> arg0, ListGroupsObj arg1, ListGroupsObj arg2) {
//                if (arg2 != null) {
//                    listGroups.setEditable(true);
//                    System.out.println("Selected Group: " + arg2.getGroupId() + " - " + arg2.getGroupName());
//                }
//            }
//        });


        listGroups.getSelectionModel().selectedItemProperty().addListener(new ChangeListener<Object>() {

            @Override
            public void changed(ObservableValue<? extends Object> ov, Object t, Object t1) {
//                 System.out.println("Selected Group:  " + t1.toString());
                 System.out.println("Selected Group : " + t1);
            }
        });

        final StackPane layout = new StackPane();
        layout.getChildren().add(listGroups);
        layout.setStyle("-fx-background-color: cornsilk; -fx-padding: 15;");
        stage.setScene(new Scene(layout));
        stage.show();
    }

    class GroupListCell extends ListCell<ListGroupsObj> {

        @Override
        protected void updateItem(ListGroupsObj item, boolean empty) {
            super.updateItem(item, empty);
            if (item != null) {
                setText(item.getGroupId() + " - " + item.getGroupName());
            }
        }
    }
//    private List<ListGroupsObj> lisGroups;

    public static class ListGroupsObj {

        private int groupId;
        private String groupName;

        public static ListGroupsObj newInstance() {
            return new ListGroupsObj();
        }

        public ListGroupsObj() {
        }

        public ListGroupsObj(int groupId, String groupName) {
            this.groupId = groupId;
            this.groupName = groupName;
        }

        public ListGroupsObj groupId(int groupId) {
            this.groupId = groupId;
            return this;
        }

        public ListGroupsObj groupName(String groupName) {
            this.groupName = groupName;
            return this;
        }

        public int getGroupId() {
            return groupId;
        }

        public String getGroupName() {
            return groupName;
        }

        @Override
        public String toString() {
            return groupId + " - " + groupName;
        }

    }
}