java - JButton在 Action 中执行

Question

if("switch".equals(action))
{
    changeLunar();
    count++;
    if (count % 2 == 0)
    {
        lunarButton = new JButton(new ImageIcon("assets/sun.png"));
    }
    else
    {
        lunarButton = new JButton(new ImageIcon("assets/moon.png"));
    }
}

因此，我试图将其放置在单击按钮的位置时，该按钮将更改为另一图像，并且再次单击该按钮时，它将返回第一图像。但是当我编译时说:

lunarButton can't be resolved to a variable

我是什么做的？

Answer 1

错误消息:找不到符号

When a Java program is being compiled the compiler creates a list of all the identifiers in use. If it can't find what an identifier refers to (e.g., there is no declaration statement for a variable) it cannot complete the compilation. This is what the cannot find symbol error message is saying, it doesn't have enough information to piece together what the Java code wants to execute.

请验证代码中声明的 lunarButton变量，并且 也必须可以访问。

可能是您已在 changeLunar()方法中将其创建为无法在方法之外访问的局部变量，而是使用 实例变量或仅 从changeLunar()方法返回值。

您不必每次都创建一个新的 JButton，而只需使用 JButton#setIcon()方法更改其图标即可。