java中的GUI,监听器不工作的私有类

时间:2010-09-13 06:24:04

标签: java user-interface inner-classes actionlistener

我正在尝试用Java创建一个GUI,使用以下内容:

public class GUIApp
{
    DrawingPanel dp;
    buttonPanel bp;
    ova = Oval;
 public GUIApp()
    {
        JFrame win = new JFrame("Drawing App");
        dp = new DrawingPanel();
        bp = new buttonPanel(this);

    //Settings for panels and frame

        ova = new Oval(100,100,100,100);

      }
      public void setOval(int c){
        //Change color of oval
      }
  }

然后在我的buttonPanel类中我有这个:

public class ButtonPanel extends JPanel
{

    private JButton btnRed, btnGreen, btnBlue;

    public ButtonPanel(GUIApp d)
    {

        ButtonListener listener = new ButtonListener();
        btnRed = new JButton("Red");
        btnGreen = new JButton("Green");
        btnBlue = new JButton("Blue");

        btnRed.addActionListener(listener);
        btnGreen.addActionListener(listener);
        btnBlue.addActionListener(listener);

        setBackground(Color.lightGray);
        GridLayout grid = new GridLayout(3,1);
        add(btnRed,grid);
        add(btnGreen,grid);
        add(btnBlue,grid);
    }

    private class ButtonListener implements ActionListener{

        public void clickButton(ActionEvent event) {
            Object location = event.getSource();
            if (location == btnRed){
                d.setOval(1);
            }
            else if(location == btnGreen){
                d.setOval(2);
            }
            else if(location == btnBlue){
                d.setOval(3);
        }
        }

}
}

但netbeans为内部ButtonListener类提供了一个错误,我不知道为什么。我也不知道如何正确地将该类中的setOval调用到GUIApp类。我做错了什么?

1 个答案:

答案 0 :(得分:3)

问题在于,当您实施ActionListener时,您必须定义方法actionPerformed(ActionEvent e);你没有在ButtonListener课程中那样做过。您无法将该方法命名为您想要的任何内容(正如您使用clickButton所做的那样),因此您应该将clickButton方法重命名为actionPerformed(并继续添加@Override注释也是如此)。

现在,为了从内部类中调用d.setOvald方法在调用actionPerformed方法时必须在范围内。有几种方法可以实现此目的:您可以将d设为您班级的成员变量,也可以将ButtonListener定义为匿名班级。

例如,如果您将d保存为成员变量,那么您的代码将如下所示:

public class ButtonPanel {
 private GUIApp d;

 public ButtonPanel(GUIApp d) {
  this.d = d;
  // The rest of your code here...
 }
}

或者,您可以使用这样的匿名类:

public ButtonPanel(GUIApp d) {
 ActionListener listener = new ActionListener(){
  @Override
  public void actionPerformed(ActionEvent event) {
   Object location = event.getSource();
   if (btnRed.equals(location)) {
    d.setOval(1);
   } else if (btnGreen.equals(location)) {
    d.setOval(2);
   } else if (btnBlue.equals(location)) {
    d.setOval(3);
   }
  }
 };
 // The rest of your constructor code here ...
}

注意:请注意我如何将==更改为equals()以实现对象相等。