Question

Java Swing中jpanel设置透明时问题

加载框是一个jpanel，设置为透明时，不知道为什么背景会出现左上角的图案，代码如下：
public JComponent getLoadingPanel2() { JPanel contentPanel = new JPanel(); JPanel msgPanel = new JPanel(); int x = (frame.getWidth() - 415) / 2; int y = (frame.getHeight() - 135) / 2; ImageIcon icon = new ImageIcon("images/715.gif"); Image image = icon.getImage().getScaledInstance(100, 100, Image.SCALE_DEFAULT); icon.setImage(image); ImageIcon closeIcon = new ImageIcon("images/window-close.png"); Image closeImage = closeIcon.getImage().getScaledInstance(16, 16, Image.SCALE_DEFAULT); closeIcon.setImage(closeImage); contentPanel.setLayout(null); contentPanel.add(msgPanel); JLabel btnCancel = new JLabel(); btnCancel.setBounds(120, 5, 35, 35); btnCancel.setIcon(closeIcon); btnCancel.setBorder(new EmptyBorder(1, 1, 1, 1)); btnCancel.setBackground(null); btnCancel.setPreferredSize(new Dimension(20, 20)); JLabel imgJLabel = new JLabel(); imgJLabel.setBounds(25, 10, 100, 100); imgJLabel.setIcon(icon); msgPanel.setLayout(null); msgPanel.add(btnCancel); msgPanel.add(imgJLabel); msgPanel.setBackground(new Color(0, 0, 0, 0)); msgPanel.setBounds(0, 0, 150, 120); msgPanel.setLocation(x, y); btnCancel.addMouseListener(new MouseAdapter() { @Override public void mouseClicked(MouseEvent e) { LoadingGlassPane.this.loadCount = 1; LoadingGlassPane.this.hidden(); } }); contentPanel.setBackground(new Color(0, 0, 0, 50)); return contentPanel; }

Answer 1

既没有重绘，也没有多一个jpanel，只出现一个左上角已经是运气了。

追问

validate()，setvisible()什么的都已经试过了，都不好用