ComboBox SAME项选择动作侦听器 [英] ComboBox SAME item selected action listener

问题描述

如果选择了DIFFERENT值，组合框将触发事件。我想也能够听到选择的SAME项目（也就是说，valueProperty没有改变）。似乎没有办法做到这一点。

A combo box will fire an event if a DIFFERENT value is selected. I want to be also be able to listen to the SAME item being selected (that is, valueProperty has no change). There seems to be no way to do this.

我试图扩展ComboBox，并找到一种方式来监听小弹出菜单被关闭，但我甚至不有权访问！我可以做什么？

I tried extending the ComboBox and finding a way to listen for the little popup menu being closed, but I don't even have access to that! What can I do?

这是我的尝试：

class ResponsiveComboBox<E> extends ComboBox<E> {

    public ResponsiveComboBox() {
        super();
        assert getContextMenu() != null; //Asssertion failed!
        this.getContextMenu().setOnHiding((WindowEvent event) -> {
            fireEvent(new ActionEvent());
        });
    }

}

推荐答案

comboBox.showingProperty().addListener((obs, wasShowing, isShowing) -> {
    if (! isShowing) {
        System.out.println("Combo box popup hidden");
    }
});

此事件处理常式可能会在更改值之前触发。

This event handler might be triggered before the value is changed.

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