java - Change Canvas to JFrame

Question

I want to change extend Canvas to JFrame. But why does my program not run? Command prompt reports:

Exception in thread "main" java.langIllegalArgumentException: 
  adding a window to a container 
  at java.awt.Container.chekNotAWindow(Container.java:483)" and so many more

Here is my code:

  class Layar extends Canvas implements Runnable,KeyListener
\\ init
    Layar()
    {
        super();
        try{
//adding a picture
            }
        catch(Exception e){}

    new Thread(this).start();
    addKeyListener(this);
    }
    public void update(Graphics g)
    {
        paint(g);
    }
    public void paint(Graphics g)
    {
        g.drawImage(img,x_back,y_back+200,null);//background

//key listener

    public void run()
    {
        //try catch
}


public class stage2
{
    public static void main(String[] args)
    {


        JFrame window = new JFrame("aaaa");
        window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        window.setLocation(50,50);
        window.setSize(700,700);
        window.setResizable(false);
        window.add(new Layar());
        window.setVisible(true);
    }
}

score 3 · Accepted Answer

本质上，一个窗口（或本例中的框架）不能添加到另一个窗口。

而不是使用

JFrame window = new JFrame("aaaa");

利用

Layar window = new Layar();

一旦您将更改为Layar从扩展JFrame。

话说回来。就个人而言，您最好简单地扩展JPanel并继续添加Layar到您创建的框架。如果您尝试从顶级容器扩展，您将从自定义绘画中获得更好的性能。

您可能还想看看Custom Painting，因为您应该覆盖paintComponentSwing 组件而不是paint

java - Change Canvas to JFrame

1 回答 1

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