英文:
Java addActionListener, multiple instance is occurring
问题
当我尝试执行comboBox_0的操作时，它会打印“red”并将comboBox_1的选定项目更改为“apple”，但它还会生成comboBox_1的操作事件，并打印“blue”。
如何执行此操作，以使程序不将更改comboBox_1项目视为生成操作事件。我不需要它打印“blue”，只需要打印“red”并更改为“apple”。
Java是否有办法区分用户进行的操作与程序本身？
抱歉，我对这个领域很陌生，无法查看讨论ActionEvents的源代码。
这是一个示例：
public void actionPerformed(ActionEvent e)
{
if(e.getSource()==comboBox_0)
{
System.out.println("red");
comboBox_1.setSelectedItem("apple");
}
else if(e.getSource()==comboBox_1)
{
System.out.println("blue");
}
else if(e.getSource()==comboBox_2)
{
System.out.println("green");
}
}
英文:
When i try to perform action for comboBox_0, it wil print "red" and change selected item on comboBox_1 as "apple", however it will also generate action event for comboBox_1 and will also print "blue".
How can i perform this so the program will not see changing comboBox_1 item as generating action event. i dont need it to print "blue", only print "red" and change to "apple".
Is there a way for java to differentiate between user conducted action vs the program itself?
Sorry, i'm new to this field and i cant check source where they discuss about ActionEvents.
here's the example:
public void actionPerformed(ActionEvent e)
{
if(e.getSource()==comboBox_0)
{
System.out.println("red");
comboBox_1.setSelectedItem("apple");
}
else if(e.getSource()==comboBox_1)
{
System.out.println("blue");
}
else if(e.getSource()==comboBox_2)
{
System.out.println("green");
}
}
答案1
得分: 1
以下是翻译好的部分：
"你正在触发一个事件，但同时你不想使用它。将标志输入到你的程序中。使用以下代码：
private boolean flag = false;
public void actionPerformed(ActionEvent e)
{
if(e.getSource()==comboBox_0)
{
System.out.println("red");
comboBox_1.setSelectedItem("apple");
flag = true;
}
else if(e.getSource()==comboBox_1)
{
if(flag){
flag = false;
return;
}
System.out.println("blue");
}
else if(e.getSource()==comboBox_2)
{
System.out.println("green");
}
}
不幸的是，无法区分事件来源（软件或用户定义的）。但这并不是必要的。如果有这样的实现，它最终也会被减少为一个“标志”。您可以使用布尔值或枚举作为标志。"
英文:
You are raising an event, but at the same time you don't want to use it. Enter the flag into your program. Use this:
private boolean flag = false;
public void actionPerformed(ActionEvent e)
{
if(e.getSource()==comboBox_0)
{
System.out.println("red");
comboBox_1.setSelectedItem("apple");
flag = true;
}
else if(e.getSource()==comboBox_1)
{
if(flag){
flag = false;
return;
}
System.out.println("blue");
}
else if(e.getSource()==comboBox_2)
{
System.out.println("green");
}
}
Unfortunately, it is not possible to distinguish the event source (software or user-defined). But it is not necessary. If there were such an implementation, it would in any case be reduced to a"flag". You can use boolean or Emun as the flag.
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