Java 图形不显示更改

Question

我正在开发一个小的 Java applet，对于这个编程来说是非常新的。使用 Java 1.6

我有一个创建多个复选框的 JPanel 的类。目标是让用户选择一些固定数量的选项，然后将这些选项传递给其他方法

public class OptionSelector extends JPanel {

private JCheckBox[] optionCheckBoxes;
private int numberSelected;
private int goalNumber;
private ArrayList<String> selectedOptions = new ArrayList<String>();
private boolean rightAmountSelected;
private boolean isFinalChoice = false;
private DoneButton done = new DoneButton();

/**
 * This method is used only for the purposes of initialization
 *
 */
public OptionSelector()
{
    this(1, "test", "test");
}

public OptionSelector(int howManyToSelect, String ... options)
{
    super(new FlowLayout());
    JCheckBox option;
    optionCheckBoxes = new JCheckBox[options.length];
    for (int i = 0; i < options.length; i++)
    {
        option = new JCheckBox(options[i]);
        optionCheckBoxes[i] = option;
        add(option);
    }
    add(done);
    numberSelected = 0;
    goalNumber = howManyToSelect;
    rightAmountSelected = false;
}

public void setOptions(String ... options)
{
    this.removeAll();
    JCheckBox option;
    optionCheckBoxes = new JCheckBox[options.length];
    for (int i = 0; i < options.length; i++)
    {
        option = new JCheckBox(options[i]);
        optionCheckBoxes[i] = option;
        add(option);
        System.out.println(option.getBounds());
    }
    add(done);
    System.out.println(done.getBounds());
}

public void paintComponent(Graphics g)
{
    g.clearRect(0,0,this.getWidth(), this.getHeight());
    for (int i = 0; i < getComponentCount(); i++)
    {
        System.out.println(this.getComponents()[i].getBounds());
    }
}

下面是我用来测试的小程序

public class TestDisplay extends JApplet implements MouseListener{

OptionSelector s = new OptionSelector();

public void init()
{
    setSize(640,480);
    this.getContentPane().setLayout(null);
    addMouseListener(this);
    s.setBounds(10,10,200,200);
    add(s);
    s.repaint();
}

public void paint(Graphics g)
{
    s.repaint();
}

public void mouseClicked(MouseEvent arg0) 
{
    s.setOptions("1","2");
    repaint();
}

public void mousePressed(MouseEvent arg0) {
    // TODO Auto-generated method stub

}

public void mouseReleased(MouseEvent arg0) {
    // TODO Auto-generated method stub

}

public void mouseEntered(MouseEvent arg0) {
    // TODO Auto-generated method stub

}

public void mouseExited(MouseEvent arg0) {
    // TODO Auto-generated method stub

}

}

问题是，当我测试小程序时，单击鼠标可以很好地更改选项，但是新的 JCheckBoxes 不会显示。尝试打印出选择器中每个组件的边界表明 JCheckBox 边界仍然卡在 (0,0,0,0)，而按钮的边界没有改变。我多次尝试重新绘制 OptionSelector 和整个小程序，但似乎没有任何效果。关于如何解决此问题的任何想法？

Answer 1

在删除和添加组件时，您似乎忘记在 JPanel 容器上调用 revalidate():

public void mouseClicked(MouseEvent arg0) {
  s.setOptions("1", "2");
  s.revalidate();
  repaint();
}

如果您希望容器(您的 JPanel)在容器中适本地布置新组件，这是必不可少的。另外，这不是一件好事:

public void paint(Graphics g) {
    s.repaint();
}

因为您无缘无故地覆盖了顶级组件的 paint 方法，也没有调用 super 方法。只需摆脱该方法即可。