Swings setSelected() 不适用于 JRadioButtons 数组 [英] Swings setSelected() not working for array of JRadioButtons

问题描述

JRadioButton opt[] = new JRadioButton[4];
opt[0].setSelected(false); //not working

JRadioButton r1 = new JRadioButton();
r1.setSelected(false); //working

谁能告诉我为什么第一次调用 setSelected() 不起作用?

Can anyone tell my why the first call to setSelected() isn't working?

推荐答案

Java Object 数组中元素的默认值为 null.JRadioButton 数组 opt 没有实例化的元素.您需要在调用任何方法之前实例化它们:

The default value for elements in a Java Object array is null. The JRadioButton array opt has no elements instantiated. You need to to instantiate them prior to invoking any methods:

for (int i=0; i < opt.length; i++) {
   opt[i] = new JRadioButton("Radio Button " + i); 
}

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