您可以通过更改 JInternalFrame 的绘制方法使用的 AlphaComposite 来做到这一点。尽管在透明组件的位置重新绘制包含顶级窗口,但您必须小心,以免产生有趣的副作用。例如:
import java.awt.*;
import javax.swing.*;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
@SuppressWarnings("serial")
public class TransparentInternalFrame extends JDesktopPane {
private static final Color COLOR_1 = Color.red;
private static final Color COLOR_2 = Color.blue;
private static final float PT_2 = 30f;
private static final int PREF_W = 800;
private static final int PREF_H = 500;
public TransparentInternalFrame() {
add(new MyInternalFrame("Foo", 50, 50, 300, 300, 0.2f));
add(new MyInternalFrame("Foo", 400, 100, 300, 300, 0.4f));
}
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
g2.setPaint(new GradientPaint(0, 0, COLOR_1, PT_2, PT_2, COLOR_2, true));
g2.fillRect(0, 0, getWidth(), getHeight());
}
@Override
public Dimension getPreferredSize() {
return new Dimension(PREF_W, PREF_H);
}
private static void createAndShowGui() {
TransparentInternalFrame mainPanel = new TransparentInternalFrame();
JFrame frame = new JFrame("TransparentInternalFrame");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(mainPanel);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGui();
}
});
}
}
@SuppressWarnings("serial")
class MyInternalFrame extends JInternalFrame {
private AlphaComposite comp = AlphaComposite.getInstance(AlphaComposite.SRC_OVER, 0.5f);
public MyInternalFrame(String title, int x, int y, int w, int h, final float alpha) {
super(title);
setClosable(true);
setBounds(x, y, w, h);
setVisible(true);
int sliderValue = (int) (alpha * 100);
comp = comp.derive(alpha);
final JSlider slider = new JSlider(0, 100, sliderValue);
slider.setMajorTickSpacing(20);
slider.setMinorTickSpacing(5);
slider.setPaintLabels(true);
slider.setPaintTicks(true);
slider.setBorder(BorderFactory.createTitledBorder("Alpha Value"));
slider.addChangeListener(new ChangeListener() {
@Override
public void stateChanged(ChangeEvent cEvt) {
float alpha = (float) slider.getValue() / 100f;
setAlpha(alpha);
MyInternalFrame.this.repaint();
Window win = SwingUtilities.getWindowAncestor(MyInternalFrame.this);
win.repaint();
}
});
add(new JLabel("My Label", SwingConstants.CENTER));
add(slider, BorderLayout.SOUTH);
}
@Override
public void paint(Graphics g) {
Graphics2D g2 = (Graphics2D) g;
g2.setComposite(comp);
super.paint(g);
}
public void setAlpha(float alpha) {
comp = comp.derive(alpha);
}
}
但请注意,该程序并未完全修复。如果将一个 JInternalFrame 拖到另一个上,您仍然会看到像素错误。我仍然需要解决错误...