为什么paintComponent执行了两次? [英] Why is paintComponent executed 2 times?

问题描述

我有以下代码:

        canvas=new MembershipFunctionComponent(functions);
        canvas.setPreferredSize(new Dimension((int)this.getWidth(), (int)this.getHeight()));
        canvas.addMouseListener(canvas);
        pane.add(canvas);

MembsershipFunctionComponent扩展了JComponent.为什么paintComponent方法执行两次?

MembsershipFunctionComponent extends JComponent. Why is paintComponent method executed 2 times?

推荐答案

paintComponent几乎可以在任何时候被Swing框架调用.何时发生这种情况的示例:

paintComponent can get called at pretty much any time by the Swing framework. Examples of when this might happen:

• 每次调整组件大小
• 显示组件的任何时间部分(例如在可滚动的窗口中)
• 每次在您的组件(或可能是父组件或子组件)上调用repaint()方法
• 每当布局发生更改时

这一切都不会让您担心-您只需要编写代码，就不必关心paintComponent被调用了多少次.

None of this should worry you - you should just write your code so that it doesn't care how many times paintComponent is called.

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