仅当字符串是数字时，Javascript才将字符串转换为数字(Javascript converting string to number only if the string is an number)

 根据你的部分代码; 
 
 1）由于滚动条的默认最大值和最小值分别为1.0和0.0，因此scrollToTop方法不会滚动到顶部。 因为您将滚动条的值设置为0.5，这意味着加载的ListView的“滚动到中心”。 
 
 2）在附加eventHandler之后，滚动条将不再移动，因为事件处理程序使用了ScrollEvent 。 scrollBar不会通过鼠标滚轮移动，但会通过鼠标拖动滚动滚动条。 
 
 3）我建议使用ListView.scrollTo()方法： 
 
private final EventHandler<ScrollEvent> scrollEventFilter = new EventHandler<ScrollEvent>() {
@Override
public void handle(ScrollEvent t) {
    if (t.getDeltaY() < 0) {
        getSelectionModel().selectNext();
    } else {
        getSelectionModel().selectPrevious();
    }

    scrollTo(lst.getSelectionModel().getSelectedIndex());

    t.consume();
  }
 
 }; 

According to your partial codes;
 
1) Since the default max and min values of scrollbar are 1.0 and 0.0 respectively, the scrollToTop method is not scrolling to top. Because you are setting the scrollbar's value to 0.5 in it, which means "scroll to center" of the loaded ListView.
 
2) After attaching the eventHandler, the scrollbar will not move any more, because the event handler consuming the ScrollEvent. The scrollBar will not move by mouse wheel, but it will scroll by mouse drag on it.
 
3) I suggest to use ListView.scrollTo() method as:
 
private final EventHandler<ScrollEvent> scrollEventFilter = new EventHandler<ScrollEvent>() {
@Override
public void handle(ScrollEvent t) {
    if (t.getDeltaY() < 0) {
        getSelectionModel().selectNext();
    } else {
        getSelectionModel().selectPrevious();
    }

    scrollTo(lst.getSelectionModel().getSelectedIndex());

    t.consume();
  }
 
};