Jpanel和图形的错误

Question

我尝试使用paint(Graphics g)代码时出错.你能帮忙解决代码,以便有一个带有3d矩形的窗口.谢谢!

private static void paint(Graphics g){
    g.draw3DRect(10, 10, 50, 50, true);

然后走向瓶底:

public static void main(String[] args) {
    //Schedule a job for the event-dispatching thread:
    //creating and showing this application's GUI.
    javax.swing.SwingUtilities.invokeLater(new Runnable() {
        public void run() {
            createAndShowGUI();
            paint();

        }
    });
}


}

Answer 1

在Java中,覆盖时不能减少方法的可见性.同样,不能进行实例方法static.它必须是

@Override
public void paint(Graphics g){
    super.paint(g);
    g.draw3DRect(10, 10, 50, 50, true);
}

在Swing中,不要在顶级窗口中进行自定义绘制,例如a JFrame.而是创建一个子类JComponent并覆盖paintComponent并确保调用super.paintComponent(g).

class MyComponent extends JComponent {

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        g.draw3DRect(10, 10, 50, 50, true);
    }

    @Override
    public Dimension getPreferredSize() {
        return new Dimension(400, 300);
    }
}

不要忘记将新组件的实例添加到JFrame:

frame.add(new MyComponent());