JRadioButton无法转换为JButton

Question

I have actionPerformed() method which does two things: print out the radio buttons selected and set visibility of labels in another class. I get cannot be cast to error when the radio button is clicked.

public void actionPerformed(ActionEvent e)
{
    System.out.println("Selected: " + e.getActionCommand());
    JButton hiddenBtn = (JButton) e.getSource();
    if (hiddenBtn == submit)
    {
        Class o = new Class();
        o.foo();
    }
    JButton close = (JButton) e.getSource();
    if (close == purchase)
    {
        System.exit(0);
    }
}

I get the error at (JButton) e.getSource() .

Answer 1

JRadioButton does not extend JButton . Therefore, you cannot cast it to a JButton . You can, however, cast to an AbstractButton .

java.lang.Object
  java.awt.Component
      java.awt.Container
          javax.swing.JComponent
              javax.swing.AbstractButton
                  javax.swing.JToggleButton
                      javax.swing.JRadioButton

Answer 2

Their least upper bound of JButton and JRadioButton is AbstractButton . You can cast to that, i think, to do what you want.

Answer 3

Besides the technical aspect of whether or not casting works, think logically on the reason behind casting a JRadioButton with a JButton. The usage of both are different.

Answer 4

In connection with AbstractButton or JButton use ButtonGroup , because if you add JRadioButton(s) to the ButtonGroup , then only one JRadioButton could be selected,

I can simulating this error about cannot be cast to javax.swing.AbstractButton or cannot be cast to javax.swing.JButton from un-correct usage renderer in the JTable