java - JComboBox itemStateChanged 事件一次调用两次

Question

resultCombo = new JComboBox();
resultCombo.addItemListener(new ItemListener() {
    @Override
    public void itemStateChanged(ItemEvent ie) {
         sampleText=resultCombo.getSelectedItem().toString();
         System.out.println("SampleText : "+sampleText);
    }
});


output:
SampleText : selectedword
SampleText : selectedword

为什么在组合框中选择项目时会调用两次此事件？

Answer 1

JComoboBox ItemListener 确实会为一次更改调用两次。一次用于 SELECTED 事件，一次用于 DESELECTED 事件。

参见 this tutorial page关于如何编写 ItemListener。

基本上你要做的是

public void itemStateChanged(ItemEvent e) {
    if (e.getStateChange() == ItemEvent.SELECTED) {
        //Do any operations you need to do when an item is selected.
    } else if(e.getStateChange() == ItemEvent.DESELECTED){
        //Do any operations you need to do when an item is de-selected.
    }
}