java - 如何使用frame.add方法创建多个可见对象

Question

当我尝试添加电梯类的第二个实例时，第一个实例消失了。如何重新排列此代码才能看到这两个对象？

这是我的主要类(class):

public class MainClass extends JPanel implements ActionListener {
    public static void main(String[] args) {
        JFrame frame = new JFrame("title");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(1000, 700);
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);

        Component component1 = frame.add(new elevator(0,0));
        Component component2 = frame.add(new elevator(505,50));   
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        // TODO Auto-generated method stub
    }
}

这是电梯类:

public class elevator extends JPanel implements ActionListener {
    Timer timer;
    private double angle = 0;
    private double scale = 1;
    private double delta = 0.01;
    private int x=0;
    private int y=0;

    Rectangle.Float r = new Rectangle.Float(0, 0, 3, 3);

    public elevator(int input_x, int input_y) {
        x=input_x;
        y=input_y;
        timer = new Timer(10, this);
        timer.start();
    }

    public elevator() {
        timer = new Timer(10, this);
        timer.start();
    }

    public void paint(Graphics g) {
        this.setSize(100,200);
        this.setLocation(x, y);
        int h = getHeight();
        int w = getWidth();

        super.paintComponent(g);

        Graphics2D g2d = (Graphics2D) g;

        g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
        g2d.setRenderingHint(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY);

        g2d.translate(w / 5, scale*140);
        g2d.scale(20, 20);

        g2d.fill(r);
    }

    public void actionPerformed(ActionEvent e) {
        if (scale < 0.01 || scale > 0.99) {
            delta = -delta;
        } 
        scale += delta;
        angle += 0.01;
        repaint();
    }
}

Answer 1

您将需要某种容器来放入这两个组件。您可以使用 JPanel，在这种情况下，您的代码将如下所示:

JPanel panel = new JPanel();
panel.add(new elevator(0,0));
panel.add(new elevator(505,50));
frame.add(panel);

为了让它们占据相同的区域(并且让 JPanel 填满它能容纳的所有空间)，您可以将 GridLayout 传递给JPanel 构造函数:

JPanel panel = new JPanel(new GridLayout(2, 1)); // 2 rows, 1 column

或

JPanel panel = new JPanel(new GridLayout(1, 2)); // 1 row, 2 columns