java - 将摆动组件绘制到图形

Question

如何将组件（如 JPanel）绘制到我选择的图形中，就好像它是屏幕一样？

在谷歌上没有运气。

我试过的：

JPanel p = new JPanel();
p.setSize(32, 32);
p.setLocation(8, 8);

p.add(new JLabel(...));
p.add(new JLabel(...));
p.add(new ImageIcon(...));

Graphics g = getSomeGraphics();
p.paint(g);

然而，这最后一条指令导致

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at javax.swing.RepaintManager.getVolatileOffscreenBuffer(Unknown Source)
    at javax.swing.RepaintManager$PaintManager.paint(Unknown Source)
    at javax.swing.BufferStrategyPaintManager.paint(Unknown Source)
    at javax.swing.RepaintManager.paint(Unknown Source)
    at javax.swing.JComponent.paint(Unknown Source)
    ...

Answer 1

此示例说明了panel.paint(g2d)如何在. 然后将图像缩放并显示在面板下方以供参考。JPanelJLabelBufferedImage

Answer 2

你可以假设我正在绘制一个 BufferedImage，事实上我有时会这样做。

请参阅Screen Image，它也可以创建组件图像。