我正在努力创建一个支持透明度的JPanel，并且遇到了一个问题，即我不确定如何将相同级别的透明度应用于添加到此面板的所有组件。到目前为止，我的代码：
package de.uebertreiberman.project.swing;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Rectangle;
import javax.swing.JPanel;
@SuppressWarnings("serial")
public class JTransparancyPanel extends JPanel {
float opacity = 1.0f;
/**Constructor for JTransparentPanel
*/
public JTransparancyPanel()
{
super();
this.setOpaque(false);
}
/**Getter for opacity value of panel
*
* @return float containing opacity value of frame (0-1)
*/
public float getOpacity()
{
return opacity;
}
/**Setter for opacity value of panel
*
* @param value as float for opacity of frame (0-1)
*/
public void setOpacity(float value)
{
opacity = value;
repaint();
}
/**Converts opacity value (0-1) to opacity color (0-255)
*
* @param opacity as float opacity value (0-1)
* @return integer containing converted opacity value (0-255)
*/
public static int getOpacityColor(float opacity)
{
return (int)(opacity * 255);
}
/**Converts opacity color (0-255) to opacity value (0-1)
*
* @param opacity as integer value (0-255)
* @return float containing converted opacity value (0-1)
*/
public static float getOpacityValue(int opacity)
{
//Returns more or less the correct, capped value
//Just ignore it, it works, leave it :D
return capFloat((3.9216f*opacity)/1000f, 0.0f, 1.0f);
}
/**Returns float capped between minimum and maximum value
*
* @param value as original value
* @param min as minimum cap value
* @param max as maximum cap value
* @return float containing capped value
*/
public static float capFloat(float value, float min, float max)
{
if(value < min) value = min;
else if(value > max) value = max;
return value;
}
/**Merges color and opacity to new color
*
* @param bg as color for old color, only RGB will be used from that
* @return color with RGB from bg and A from opacity of frame
*/
Color getTransparencyColor(Color bg)
{
return new Color(getOpacityValue(bg.getRed()), getOpacityValue(bg.getGreen()), getOpacityValue(bg.getBlue()), opacity);
}
@Override
public void paintComponent(Graphics g)
{
//Draw transparent background before painting other Components
g.setColor(getTransparencyColor(getBackground()));
Rectangle r = g.getClipBounds();
g.fillRect(r.x, r.y, r.width, r.height);
//Paint other components
super.paintComponent(g);
}
}
重要的部分基本上是在最后，我覆盖了画家组件（Graphics g）方法。
我只需要使用背景颜色，对其应用透明度并进行设置。
现在我想让这个面板的所有组件子项也变得透明，我不太确定什么是最有效的方法。
你有什么建议？
我找到了一个解决方案——基本上我已经在评论中提到了：面板并没有真正绘制在屏幕上。相反，它被绘制成一个图像，并且这个图像是用适当的AlphaCom的绘制的。
（滑块可用于设置面板的不透明度）
虽然这个解决方案简单、通用，基本上可以与所有子组件一起使用，但有一点我不喜欢：调整RepaintManager的必要性。为了确保应用面板的不透明度（并且子组件不是独立绘制的，并且具有完全的不透明度），重新绘制管理器必须在重新绘制子组件时触发整个组件的重新绘制。我认为应该有没有这种解决方法的解决方案（例如，这可能是在面板上覆盖getGaphics可能是合适的罕见情况之一），但没有用。也许通常的嫌疑人（camickr、气垫船等）找到了一个更优雅、更简洁的解决方案。
在此之前，以下是作为MCVE的代码：
import java.awt.AlphaComposite;
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Component;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import javax.swing.JButton;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JSlider;
import javax.swing.JTree;
import javax.swing.RepaintManager;
import javax.swing.SwingUtilities;
public class TransparencyPanelTest
{
public static void main(String[] args)
{
SwingUtilities.invokeLater(() -> createAndShowGui());
}
private static void createAndShowGui()
{
JFrame f = new JFrame();
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.getContentPane().setLayout(new BorderLayout());
OpacityPanel opacityPanel = new OpacityPanel();
opacityPanel.setLayout(new BorderLayout());
opacityPanel.add(new JLabel("Label"), BorderLayout.NORTH);
opacityPanel.add(new JTree(), BorderLayout.CENTER);
opacityPanel.add(new JButton("Button"), BorderLayout.SOUTH);
f.getContentPane().add(opacityPanel, BorderLayout.CENTER);
JSlider slider = new JSlider(0, 100, 50);
slider.addChangeListener(e ->
opacityPanel.setOpacity(slider.getValue() / 100.0f));
f.getContentPane().add(slider, BorderLayout.SOUTH);
f.setSize(500,500);
f.setLocationRelativeTo(null);
f.setVisible(true);
}
}
class OpacityPanel extends JPanel
{
static
{
RepaintManager.setCurrentManager(new RepaintManager()
{
@Override
public void addDirtyRegion(
JComponent c, int x, int y, int w, int h)
{
Component cc = c;
while (cc != null)
{
if (cc instanceof OpacityPanel)
{
OpacityPanel p = (OpacityPanel)cc;
super.addDirtyRegion(
p, 0, 0, p.getWidth(), p.getHeight());
}
cc = cc.getParent();
}
super.addDirtyRegion(c, x, y, w, h);
}
});
}
private float opacity = 0.5f;
private BufferedImage image;
public OpacityPanel()
{
setOpaque(false);
}
public void setOpacity(float opacity)
{
this.opacity = Math.max(0.0f, Math.min(1.0f, opacity));
repaint();
}
private void updateImage()
{
int w = Math.min(1, getWidth());
int h = Math.min(1, getHeight());
if (image == null || image.getWidth() != w || image.getHeight() != h)
{
image = new BufferedImage(w, h, BufferedImage.TYPE_INT_ARGB);
}
Graphics2D g = image.createGraphics();
g.setColor(new Color(0,0,0,0));
g.setComposite(AlphaComposite.SrcOver);
g.fillRect(0, 0, w, h);
g.dispose();
}
@Override
protected void paintComponent(Graphics gr)
{
updateImage();
Graphics2D imageGraphics = image.createGraphics();
super.paintComponent(imageGraphics);
imageGraphics.dispose();
Graphics2D g = (Graphics2D) gr;
g.setComposite(AlphaComposite.getInstance(
AlphaComposite.SRC_OVER, opacity));
g.drawImage(image, 0, 0, null);
}
}
3楼的答案很棒，但是我认为我们可以不重写重绘管理器，我们可以将面板设置为非不透明，或者在所需的Settings中将子组件设置为非不透明，如下图
for (Component c : panel.getComponents()) {
((JComponent)c).setOpaque(false);
}
