在JPanel上添加.GIF时显示的黑色方块 [英] Black square showing when adding a .GIF on JPanel
问题描述
我的问题是，当将.GIF添加到JPanel时，它会显示.GIF的黑色方形背景。
My problem is that when adding a .GIF to a JPanel, it shows this black square background for the .GIF.
在JPanel上添加时的结果：
当我使用这一行时会发生这种情况：
It happens when I use this line:
p2.add(loadBar); // where p2 = new JPanel();
然而，当我在JFrame上添加相同的.GIF时，黑色正方形不再存在。像这样：
However, when I add the same .GIF on the JFrame, the black square is not there anymore. Like this:
jf.add(loadBar); // where jf = new JFrame();
在JFrame上添加时的结果：
类代码的一部分：
String loadLink = "http://i.imgur.com/mHm6LYH.gif";
URL ajaxLoad = null;
try {
ajaxLoad = new URL(loadLink);
} catch (MalformedURLException e3) {
// TODO Auto-generated catch block
e3.printStackTrace();
}
ImageIcon loading = new ImageIcon(ajaxLoad);
JLabel loadBar = new JLabel(loading);
loadBar.setBounds(70, 60, 54, 55);
loadBar.setOpaque(false);
//jf.add(loadBar);
p2.add(loadBar);
有人可以解释为什么会这样吗？感谢您的时间和阅读。
Could someone please explain why it is happening like this? Thank you for your time and reading.
编辑：
// Creates the Initialization Panel
p2 = new JPanel();
// Sets the background, black with 125 as alpha value
// This is less transparent
p2.setLayout(null);
p2.setBackground(new Color(0,0,0,150));
// Sets a border to the JPanel
p2.setBorder(new LineBorder(Color.WHITE));
// Sets some size to the panels
p2.setBounds(20, 20, 200, 150);
// Adds the loading gif
String loadLink = "http://i.imgur.com/mHm6LYH.gif";
URL ajaxLoad = null;
try {
ajaxLoad = new URL(loadLink);
} catch (MalformedURLException e3) {
// TODO Auto-generated catch block
e3.printStackTrace();
}
ImageIcon loading = new ImageIcon(ajaxLoad);
JLabel loadBar = new JLabel(loading);
loadBar.setBounds(70, 60, 54, 55);
loadBar.setOpaque(false);
p2.add(loadBar);
这是没有JLabel的第一张图片中显示的JPanel。我无法在代码中真正显示JFrame部分，因为它遍布整个类。但我认为问题不在于JFrame，所以它可能是这个JPanel：/
That is the JPanel which is shown in the first image without the JLabel. I can't really show the JFrame part in the code because it is spread all over the class. But I don't think the problem is with JFrame so it could be this JPanel :/
推荐答案
你的问题在这里.. 。
Your problem is here...
p2.setBackground(new Color(0,0,0,150));
Swing不支持基于alpha的背景，要么你的组件是透明的，要么不是。
Swing does not support alpha based backgounds, either your component is transparent or it's not.
这样做意味着组件尝试使用alpha值作为背景填充颜色，但是油漆管理器不知道它应该在组件下面绘制，导致各种各样的问题和问题
Doing this means that the component "attempts" to use the alpha value as the background fill color, but the paint manager doesn't know it should paint beneath the component, causing all sorts of problems and issues
现在，这有点棘手。您需要使用 setOpaque（false）使容器透明，但现在这意味着背景未绘制。
Now, this a little tricky. You need to make the container transparent by using setOpaque(false), but this now means that the background is not painted.
您需要做的是创建一个自定义组件，将其 opaque 属性设置为 false 并覆盖它 paintComponent 方法并使用基于alpha的颜色填充背景。我通常喜欢使用 AlphaComposite ，但这也可以... ...
What you need to do is create a custom component, set it's opaque property to false and override it's paintComponent method and fill the background with your alpha based color. I normally like using a AlphaComposite, but this works as wel...
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.GridBagLayout;
import java.awt.HeadlessException;
import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;
import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.border.EmptyBorder;
public class TranslucentPanelExample {
public static void main(String[] args) {
new TranslucentPanelExample();
}
public TranslucentPanelExample() {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
}
try {
JLabel background = new JLabel(
new ImageIcon(ImageIO.read(
getClass().getResource("/background.jpg"))));
background.setLayout(new GridBagLayout());
background.add(new WaitPane());
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(background);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
} catch (IOException exp) {
exp.printStackTrace();
}
}
});
}
public class WaitPane extends JPanel {
public WaitPane() {
setLayout(new GridBagLayout());
setBorder(new EmptyBorder(12, 12, 12, 12));
// This is very important
setOpaque(false);
setBackground(new Color(0, 0, 0, 150));
String loadLink = "http://i.imgur.com/mHm6LYH.gif";
URL ajaxLoad = null;
try {
ajaxLoad = new URL(loadLink);
} catch (MalformedURLException e3) {
// TODO Auto-generated catch block
e3.printStackTrace();
}
ImageIcon loading = new ImageIcon(ajaxLoad);
JLabel loadBar = new JLabel(loading);
loadBar.setHorizontalAlignment(JLabel.CENTER);
loadBar.setVerticalAlignment(JLabel.CENTER);
add(loadBar);
}
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
g.setColor(getBackground());
g.fillRect(0, 0, getWidth(), getHeight());
}
}
}
布局管理器，布局管理器，布局管理器...
Layout managers, layout managers, layout managers...
我不能强调布局管理器的重要性。你依赖的是魔法数字，这些数字可能并不总是符合现实......
I can't stress enough how important layout managers are. You are relying on "magic" numbers which may not always meet reality...
这篇关于在JPanel上添加.GIF时显示的黑色方块的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
