java - 图形是在 java swing 中绘制在 UI 之上的，

Question

当我在 paint() 方法中在 Jpanel 上绘图时(通过继承 JPanel)
图形出现在我的按钮和其他 UI 组件的顶部，
在不可见的组件中，那么如何在图形之上绘制组件呢？

Answer 1

首先查看 Performing Custom Painting和 Painting in AWT and Swing

The Paint Methods
The rules that apply to AWT's lightweight components also apply to Swing components -- for instance, paint() gets called when it's time to render -- except that Swing further factors the paint() call into three separate methods, which are invoked in the following order:
<br/>protected void paintComponent(Graphics g)<br/>
protected void paintBorder(Graphics g) <br/>
protected void paintChildren(Graphics g)<br/>

Swing programs should override paintComponent() instead of overriding paint(). Although the API allows it, there is generally no reason to override paintBorder() or paintComponents() (and if you do, make sure you know what you're doing!). This factoring makes it easier for programs to override only the portion of the painting which they need to extend. For example, this solves the AWT problem mentioned previously where a failure to invoke super.paint() prevented any lightweight children from appearing.