[英]Java Swing: Transparent PNG permanently captures original background
我有以下代码:
import javax.swing.JWindow;
import javax.swing.ImageIcon;
import javax.swing.JOptionPane;
import java.awt.Graphics;
import java.awt.Image;
import java.awt.Toolkit;
public class sutff extends JWindow
{
//Get transparent image that will be use as splash screen image.
Image bi=Toolkit.getDefaultToolkit().getImage("window.png");
ImageIcon ii=new ImageIcon(bi);
public sutff()
{
try
{
setSize(ii.getIconWidth(),ii.getIconHeight());
setLocationRelativeTo(null);
show();
//Thread.sleep(10000);
//dispose();
//JOptionPane.showMessageDialog(null,"This program will exit !!!","<>",JOptionPane.INFORMATION_MESSAGE);
}
catch(Exception exception)
{
exception.printStackTrace();
}
}
//Paint transparent image onto JWindow
public void paint(Graphics g)
{
g.drawImage(bi,0,0,this);
}
public static void main(String[]args)
{
sutff tss=new sutff();
}
}
目的是创建一个半透明的窗口,类似于Windows Aero风格的玻璃。 我正在使用以下透明png: http : //i.imgur.com/5UNGbsr.png
问题在于,由于它是透明的,因此它应该显示在窗口后面的东西,对吗? 这就是第一次执行时的操作,除了首次启动时该“透明窗口”后面的任何窗口外,程序都会以某种方式创建该“透明窗口”并将其永久地附加在该窗口上。 因此,即使我最小化了该“透明窗口”后面的窗口,第一个背景窗口的图像仍然保留。
这是屏幕截图:
截屏时,我已经最小化了可以在后台看到的命令提示符和IDE,但仍保留在窗口的背景中。
我究竟做错了什么?
不要覆盖顶级容器的paint()方法,尤其是当您不调用super.paint()时。 这将导致绘画问题。 如果确实需要进行自定义绘制,则应重写JPanel(或JComponent)的paintComponent()方法,然后将面板添加到窗口/框架。 阅读有关“自定义绘画”的Swing教程。 每天都会提供此建议,我不知道为什么人们仍然尝试覆盖paint()????
但是,这只是您的问题之一。 更好的解决方案是将图像添加到JLabel,然后将标签添加到窗口。 您还需要使窗口背景透明:
import javax.swing.*;
import javax.swing.ImageIcon;
import javax.swing.JOptionPane;
import java.awt.*;
import java.awt.Image;
import java.awt.Toolkit;
public class Stuff extends JWindow
{
//Get transparent image that will be use as splash screen image.
Image bi=Toolkit.getDefaultToolkit().getImage("transparent.png");
ImageIcon ii=new ImageIcon(bi);
public Stuff()
{
try
{
setBackground( new Color(0, 0, 0, 0) );
setSize(ii.getIconWidth(),ii.getIconHeight());
setLocationRelativeTo(null);
JLabel label = new JLabel(ii);
add(label);
show();
//Thread.sleep(10000);
//dispose();
//JOptionPane.showMessageDialog(null,"This program will exit !!!","<>",JOptionPane.INFORMATION_MESSAGE);
}
catch(Exception exception)
{
exception.printStackTrace();
}
}
/*
//Paint transparent image onto JWindow
public void paint(Graphics g)
{
super.paint(g);
g.drawImage(bi,0,0,this);
}
*/
public static void main(String[]args)
{
Stuff tss=new Stuff();
}
}
问题是,您的窗口实际上是透明的。 Java仍然认为Window是不透明的,因此不会更新图形以显示实际的内容。
从Java 1.6.10开始,在Java中创建透明窗口相对简单(我认为)
以下是一个非常简单的示例,使用半透明的绘画效果,使落在窗口下方的所有内容都能继续正确绘画。
import com.sun.awt.AWTUtilities;
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Shape;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.geom.RoundRectangle2D;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class TransaprentBlur {
public static void main(String[] args) {
new TransaprentBlur();
}
public TransaprentBlur() {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
}
JFrame frame = new JFrame("Testing");
frame.setUndecorated(true);
frame.setBackground(new Color(0, 0, 0, 0));
// Java 6...
// AWTUtilities.setWindowOpaque(frame, true);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(new BorderLayout());
frame.add(new TestPane());
frame.setSize(400, 400);
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class TestPane extends JPanel {
public TestPane() {
setOpaque(false);
addMouseListener(new MouseAdapter() {
@Override
public void mouseClicked(MouseEvent e) {
if (e.getClickCount() == 2) {
System.exit(0);
}
}
});
}
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Shape shape = new RoundRectangle2D.Float(0, 0, getWidth() - 1, getHeight() - 1, 20, 20);
Graphics2D g2d = (Graphics2D) g.create();
g2d.setColor(new Color(225, 225, 225, 128));
g2d.fill(shape);
g2d.setColor(Color.GRAY);
g2d.draw(shape);
g2d.dispose();
}
}
}
图片更新示例
屏幕截图显示了窗口已移到窗口后面。
基本上,您所需要做的就是将图像渲染代码放置在TestPane
的paintComponent
方法中
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.image.BufferedImage;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class TransaprentBlur {
public static void main(String[] args) {
new TransaprentBlur();
}
public TransaprentBlur() {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
}
JFrame frame = new JFrame("Testing");
frame.setUndecorated(true);
frame.setBackground(new Color(0, 0, 0, 0));
// Java 6...
// AWTUtilities.setWindowOpaque(frame, true);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(new BorderLayout());
frame.add(new TestPane());
frame.setSize(400, 400);
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class TestPane extends JPanel {
private BufferedImage image;
public TestPane() {
try {
image = ImageIO.read(getClass().getResource("/5UNGbsr.png"));
} catch (IOException ex) {
}
setOpaque(false);
addMouseListener(new MouseAdapter() {
@Override
public void mouseClicked(MouseEvent e) {
if (e.getClickCount() == 2) {
System.exit(0);
}
}
});
}
@Override
public Dimension getPreferredSize() {
return image == null ? super.getPreferredSize() : new Dimension(image.getWidth(), image.getHeight());
}
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
if (image != null) {
Graphics2D g2d = (Graphics2D) g.create();
int x = (getWidth() - image.getWidth()) / 2;
int y = (getHeight() - image.getHeight()) / 2;
g2d.drawImage(image, x, y, this);
g2d.dispose();
}
}
}
}
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