ActionListener和ChangeListener更改paintComponent无效

Question

用户假设键入一个字符串以更改打印的文本，并更改​​滑块以更改圆圈的大小。 但是滑块和文本字段都没有任何响应。

组件（滑块，文本字段，字符串，圆圈）全部打印出来，但是它什么都没有响应

paintComponent

public void paintComponent(Graphics g)
{
    super.paintComponent(g);

    g.drawString(text,100,10);
    g.fillOval(100,100,circleSize,circleSize);
}

文本域

class TextfieldPanel extends JPanel
{
    public TextfieldPanel()
    {
        TextfieldHandler thandler = new TextfieldHandler();
        textfield = new JTextField("enter",10);
        add(textfield);
        textfield.addActionListener(thandler);
    }

    class TextfieldHandler implements ActionListener
    {
        public void actionPerformed(ActionEvent evt)
        {
            String input = textfield.getText();
            text = input;
            repaint();
        }
    }

}

滑杆

class SliderPanel extends JPanel
{
    public SliderPanel()
    {
        SliderHandler shandler = new SliderHandler();
        slider = new JSlider(JSlider.VERTICAL);
        add(slider);
        slider.addChangeListener(shandler);
    }

    class SliderHandler implements ChangeListener
    {
        public void stateChanged(ChangeEvent evt)
        {
            int value = slider.getValue();
            circleSize = value;
            repaint();
        }
    }


}