我正在尝试使用“child”JPanel
创建一个基座JPanels
,其中包含透明矩形,用于显示基座JPanel
的背景。
我似乎只能在我的孩子和基地JPanel
中创建透明的矩形。有没有办法告诉java只能在我的孩子JPanels
上绘制不透明的部分JPanel
并忽略透明部分?
简而言之,我希望图片中的黑色矩形为青色(基础JPanel
的背景颜色)。
JFrame
:
import java.awt.AlphaComposite;
import java.awt.Color;
import java.awt.Component;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;
import java.awt.image.BufferedImage;
import java.beans.Transient;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.AbstractAction;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.KeyStroke;
public class Showcase extends JFrame{
public static void main(String[] args) {
Showcase window = new Showcase();
}
public Showcase() {
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
final JPanel contentPane = new JPanel();
contentPane.setBackground(Color.CYAN);
setContentPane(contentPane);
final TestPane tP = new TestPane();
contentPane.add(tP);
tP.setBackground(Color.BLUE);
setVisible(true);
pack();
}
@Override
public Dimension getPreferredSize() {
return new Dimension(500, 300);
}
public class TestPane extends JPanel{
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
g2.setBackground(new Color(0, 0, 0, 0));
g2.clearRect(0, 0, 50,50);
g2.dispose();
}
@Override
@Transient
public Dimension getPreferredSize() {
return new Dimension(100, 100);
}
}
}
答案 0 :(得分:2)
有没有办法告诉java只绘制不透明的部分
首先,您需要使面板不透明,以便绘制父背景。
然后你可以使用Area
类来创建你想要绘制的Shape
:
public class TestPane extends JPanel
{
public TestPane()
{
setOpaque( false ); // to make it transparent.
}
@Override
protected void paintComponent(Graphics g)
{
super.paintComponent(g);
/*
Graphics2D g2 = (Graphics2D) g;
g2.setBackground(new Color(0, 0, 0, 0));
g2.clearRect(0, 0, 50,50);
g2.dispose();
*/
Graphics2D g2d = (Graphics2D) g.create();
Shape outer = new Rectangle(0, 0, getWidth(), getHeight());
Shape inner = new Rectangle(0, 0, 50, 50);
Area area = new Area( outer );
area.subtract( new Area(inner) );
g2d.setColor( getBackground() );
g2d.fill(area);
g2d.dispose();
}
@Override
@Transient
public Dimension getPreferredSize() {
return new Dimension(100, 100);
}
}
答案 1 :(得分:1)
您可以使用setOpaque()
使JPanel
的背景透明,但是您无法绘制想要透明的矩形。
另一种方法是制作BufferedImage
并在该图片上绘制矩形,然后将BufferedImage
添加到JPanel
。
import java.awt.AlphaComposite;
import java.awt.Color;
import java.awt.Component;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;
import java.awt.image.BufferedImage;
import java.beans.Transient;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.AbstractAction;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.KeyStroke;
public class Showcase extends JFrame {
BufferedImage img;
public static void main(String[] args) {
Showcase window = new Showcase();
}
public Showcase() {
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
final JPanel contentPane = new JPanel();
contentPane.setBackground(Color.CYAN);
setContentPane(contentPane);
final TestPane tP = new TestPane();
contentPane.add(tP);
// make new buffered image
img = new BufferedImage(tP.getPreferredSize().width,
tP.getPreferredSize().height, BufferedImage.TYPE_INT_ARGB);
setVisible(true);
pack();
}
@Override
public Dimension getPreferredSize() {
return new Dimension(500, 300);
}
public class TestPane extends JPanel{
@Override
protected void paintComponent(Graphics g) {
Graphics2D g2 = (Graphics2D) g;
Graphics2D imgG2 = img.createGraphics();
// make img background transparent
imgG2.setBackground(new Color(0,0,0,0));
imgG2.setColor(Color.red);
imgG2.fillRect(0, 0, 100, 100);
imgG2.clearRect(0, 0, 50, 50);
imgG2.dispose();
// draw buffered image to jpanel
g2.drawImage(img, 0, 0, null);
g2.dispose();
super.paintComponent(g);
}
@Override
@Transient
public Dimension getPreferredSize() {
return new Dimension(100, 100);
}
}
}
最终结果如下: