Panel.repaint（）;弄乱了布局 [英] Panel.repaint(); messes up layout

问题描述

JPanel Initiation

JPanel Initiation

    p = new JPanel() {
        private static final long serialVersionUID = 1L;
        public void paintComponent(Graphics g) {
            if(errors == 1)
                g.drawOval(215, 50, 75, 75);
            else if(errors == 2)
                g.drawOval(200,200,200,200);
        }
    };

调用重绘的方法

static void drawHead() {
    System.out.println("Head");
    errors = 1;
    p.removeAll();
    p.revalidate();
    p.repaint();
}

在重绘之前 my框架看起来像这样， http://i.imgur.com/XQlQeul.png

Before repaint my frame looks like this, http://i.imgur.com/XQlQeul.png

之后看起来像这样， http：// i。 imgur.com/RnVuUzt.png

我认为我的 drawHead（）中存在错误方法，但我似乎无法解决问题。有谁知道发生了什么？我想要的结果将是第一张图片，但是用头绘制。

I'm thinking there is an error in my drawHead() method but I cannot seem to resolve the issue. Does anyone know what is going on? My desired outcome would be the first image, but with a head drawn in.

推荐答案

您在执行任何自定义绘画之前未能先调用 super.paintComponent 打破了绘画链

You've broken the paint chain by failing to call super.paintComponent first before you performed any custom painting

Graphics 是共享资源，在绘制周期中绘制的每个组件将共享相同的 Graphics 上下文，这意味着除非您清除它，否则以前绘制到 Graphics 上下文的任何内容都将保留。

Graphics is shared resource, every component painted in a during a paint cycle will share the same Graphics context, this means that whatever was previously painted to the Graphics context will remain unless you clear it.

其中一个作业 paintComponent 是通过填充组件的背景颜色来为绘画准备 Graphics 上下文

One of the jobs of paintComponent is to prepare the Graphics context for painting by filling it with the background color of the component

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