我在oracle论坛上发现了这个。
public class TextFieldWithprompt extends JTextField{@Overrideprotected void paintComponent(java.awt.Graphics g) { super.paintComponent(g); if(getText().isEmpty() && ! (FocusManager.getCurrentKeyboardFocusManager().getFocusOwner() == this)){ Graphics2D g2 = (Graphics2D)g.create(); g2.setBackground(Color.gray); g2.setFont(getFont().deriveFont(Font.ITALIC)); g2.drawString("zip", 5, 10); //figure out x, y from font's FontMetrics and size of component. g2.dispose(); } }https://forums.oracle.com/forums/thread.jspa?threadID=1349874
