如何删除事件处理程序上的所有标签，请单击

Question

I have an event handler which I would like to clear all labels of result before printing the new labels. I would like to keep the other labels that are not of type result. The code is currently only clearing the last instance of result. What loop do I need to add?

@Override
public void handle(ActionEvent event) { 
    listLayout.getChildren().removeAll(result);
    Collections.sort(listOfCars, ListYears.yearCom);

    for (int i = 0; i < listOfCars.size(); i++) {
        newCarsListings = listOfCars.get(i).toString();
        result = new Label(newCarsListings);
        result.setTranslateX(20);
        result.setTranslateY(-40);
        listLayout.getChildren().addAll(result);
    }
}

Answer 1

The problem is that you create the label "result" for every car you have in your listOfCars . So your first line listLayout.getChildren().removeAll(result) will only remove the last created Label. If you have 10 cars in your list, you will create 10 Label objects, but only the last one can be referenced via result .

If you want to remove all your created Labels (and no other controls), I suggest you introduce a subclass of Label :

class CarLabel extends Label {
    CarLabel(String str) {
        super(str);
    }
}

And then in your handle method:

public void handle(ActionEvent event) {
    listLayout.getChildren().removeIf(CarLabel.class::isInstance);
    Collections.sort(listOfCars, ListYears.yearCom);
    for(Object o : listOfCars) {
        result = new CarLabel(o.toString());
        result.setTranslateX(20);
        result.setTranslateY(-40);
        listLayout.getChildren().add(result);
    }
}

Answer 2

removeAll(result) will only remove the elements in listLayout.getChildren() that are matching an element from result .

Have a look at the official documention for removeAll

If you want to remove every element the list is containing use the clear() method

            @Override
            public void handle(ActionEvent event) { 

                listLayout.getChildren().clear()
                // the list should be empty now
                Collections.sort(listOfCars, ListYears.yearCom);

                for (int i = 0; i < listOfCars.size(); i++) {

                newCarsListings = listOfCars.get(i).toString();

                result = new Label(newCarsListings);
                result.setTranslateX(20);
                result.setTranslateY(-40);

                listLayout.getChildren().addAll(result);

                }
            }
          });