在Swing中获取当前外观组件背景颜色的正确方法是什么？

Question

I am writing a custom Swing component with my own painting. I'd like to query whether or not the current look and feel's components are opaque, and if so, what their background color is so my component can use it too. I'm having a hard time finding that on Google. Anyone know? Thanks!

Answer 1

That's pretty simple:

public class MyComponent extends JComponent {

    public void paintComponent(Graphics g) {

        if (this.isOpaque()) {
            // Paint background
            g.setColor(this.getBackground());
            g.fillRect(0,0,this.getWidth(), this.getHeight());
        }

        g.setColor(this.getForeground());
        // Continue painting
    }
}

Answer 2

Don't really understand the question. Each component can have a different background color so what background color do you want your custom component to use?

I would guess generally speaking the background color of a LAF would be determined by a JPanel, so I guess your custom component could just extend JPanel and you don't have to worry about this.

If you want to query the default backgroud colors of every component then you can use the UIManager to look it up. See the UIManager Defaults example.