java – 使用BorderLayout将图形添加到JFrame中

编辑：现在可以编译的代码列表：

import java.awt.BorderLayout;
    import java.awt.Color;
    import java.awt.Dimension;
    import java.awt.Graphics;
    import java.awt.event.ActionEvent;
    import java.awt.event.ActionListener;

    import javax.swing.JButton;
    import javax.swing.JFrame;
    import javax.swing.JPanel;
    import javax.swing.JTextField;

    public class Test {

    public static void main(String[] args) {

        // Creates new JFrame called frame,with title "Door" 
        // (displayed at top of screen).
        JFrame frame = new JFrame ("Door");
        frame.setDefaultCloSEOperation(JFrame.EXIT_ON_CLOSE);

        TempDoorPanel panel = new TempDoorPanel();
        frame.add(panel);
        frame.pack();
        frame.setVisible(true);

        }
    }

    class Door {

    private String state;
    private String message;

    Door (String state) {
        this.state = state;
        message = "The door is currently closed.";
    }

    public boolean isOpen() {
        return state.equals ("open");
    }

    public boolean isClosed() {
        return state.equals ("closed");
    }

    public void setState(String state) {
        this.state = state;
    }

    public String getMessage() {
        return message; 
    }

    public void open() {
        if (state.equals("open")) {
            message = "The door is already open.";
        }
        else {
            state = "open";
            message = "The door has been opened.";
        }
    }

    public void drawOpenDoor (Graphics page) {
        page.drawRect(100,100,100);
    }
    }

    class TempDoorPanel extends JPanel {

    private Door door;
    private JTextField currentStateOfDoor;
    private JButton openDoor;

    public TempDoorPanel() {
        super.setLayout(new BorderLayout());
        door = new Door("closed");
        super.setBackground(Color.blue);
        super.setPreferredSize(new Dimension (360,400));

        currentStateOfDoor = new JTextField(14);
        currentStateOfDoor.setText(door.getMessage());
        super.add(currentStateOfDoor,BorderLayout.NORTH);

        openDoor = new JButton("Open Door");

        class openDoorListener implements ActionListener {
            public void actionPerformed (ActionEvent event) {
                door.open();
                repaintText();
            }
        }

        openDoorListener openlistener = new openDoorListener();
        openDoor.addActionListener(openlistener);

        JPanel holder = new JPanel();
        holder.add(openDoor);
        super.add(holder,BorderLayout.SOUTH);
    }

    private void repaintText() {
        currentStateOfDoor.setText(door.getMessage());
        // These methods are from Door class.
    }

    public void paintComponent (Graphics page) {
        super.paintComponent(page);
        if (door.isOpen())
            door.drawOpenDoor(page);
        // isOpen is a boolean method from Door class.
    }
}

什么有效：

>按钮出现在屏幕上的正确位置,在BorderLayout.SOUTH,一个接一个.
> JTextField出现在BorderLayout.NORTH的正确位置
>最后,蓝色区域出现在屏幕中央的正确位置.

我正在努力解决的问题：

>我不知道如何在蓝色区域的中间正确显示矩形.我试过改变矩形的坐标和大小,这根本不会改变它的大小.我可以把它作为drawRect(100,100)并且它什么都不改变.
>我也知道矩形当前隐藏在JTextField的左上角后面,但我无法弄清楚如何将它移动到BorderLayout中.

问题：

>如何在BorderLayout中放置一个矩形？
>在这样的布局中,如何调整通过drawrect()绘制的矩形的大小？