我是Java的新手，我正在尝试在Swing中创建一个程序。除了背景图像没有显示外，一切正常。添加背景图像的代码似乎很好（我得到了帮助）。我主要关注的是我放置了BackgroundPanel类和我调用的类的实例（在main中，这是主文档中唯一引用BackgroundPanel的地方）。我还为BackgroundPanel类本身提供了一个单独的文档（下面粘贴了两个文档）。
有人可以指导我朝正确的方向前进吗？我取消了导入和包装信息，因为他们在这里占用了大量空间。谢谢！
这是我的主要代码：
public class InvitationCard extends JFrame {
private JPanel contentPane;
private JTextField txtMood;
private JPanel panel;
private JTextPane textPaneBody;
private JTextPane textPaneNames;
/**
* Launch the application.
*/
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
InvitationCard frame = new InvitationCard();
frame.setVisible(true);
BackgroundPanel BP = new BackgroundPanel();
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
/**
* Create the frame.
*/
public InvitationCard() {
setBackground(Color.WHITE);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setBounds(100, 100, 637, 490);
contentPane = new JPanel();
contentPane.setBackground(Color.WHITE);
contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
setContentPane(contentPane);
GridBagLayout gbl_contentPane = new GridBagLayout();
gbl_contentPane.columnWidths = new int[] { 0, 0, 0, 0 };
gbl_contentPane.rowHeights = new int[] { 0, 0, 0, 0, 0, 0 };
gbl_contentPane.columnWeights = new double[] { 0.0, 0.0, 0.0, 1.0 };
gbl_contentPane.rowWeights = new double[] { 1.0, 0.0, 1.0, 0.0, 0.0,
Double.MIN_VALUE };
contentPane.setLayout(gbl_contentPane);
panel = new JPanel();
GridBagConstraints gbc_panel = new GridBagConstraints();
gbc_panel.fill = GridBagConstraints.VERTICAL;
gbc_panel.anchor = GridBagConstraints.WEST;
gbc_panel.gridwidth = 2;
gbc_panel.gridheight = 5;
gbc_panel.insets = new Insets(0, 0, 0, 5);
gbc_panel.gridx = 0;
gbc_panel.gridy = 0;
contentPane.add(panel, gbc_panel);
GridBagLayout gbl_panel = new GridBagLayout();
gbl_panel.columnWidths = new int[] { 130, 0 };
gbl_panel.rowHeights = new int[] { 26, 0, 0, 0 };
gbl_panel.columnWeights = new double[] { 0.0, Double.MIN_VALUE };
gbl_panel.rowWeights = new double[] { 0.0, 0.0, 0.0, Double.MIN_VALUE };
panel.setLayout(gbl_panel);
Font font1 = new Font("Helvetica", Font.BOLD, 12);
Font font2 = new Font("Courier", Font.BOLD, 12);
Font font3 = new Font("nouradilla.regular", Font.BOLD, 12);
Font font4 = new Font("GearedSlab-Bold", Font.PLAIN, 12);
txtMood = new JTextField();
GridBagConstraints gbc_txtMood = new GridBagConstraints();
gbc_txtMood.insets = new Insets(0, 0, 5, 0);
gbc_txtMood.anchor = GridBagConstraints.NORTHWEST;
gbc_txtMood.gridx = 0;
gbc_txtMood.gridy = 1;
panel.add(txtMood, gbc_txtMood);
txtMood.setEditable(false);
txtMood.setText("Mood: ");
txtMood.setColumns(10);
JComboBox comboBox = new JComboBox();
GridBagConstraints gbc_comboBox = new GridBagConstraints();
gbc_comboBox.gridx = 0;
gbc_comboBox.gridy = 2;
panel.add(comboBox, gbc_comboBox);
comboBox.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
// get item from dropdown
String item = (String) comboBox.getSelectedItem();
if (item == "Whimsical") {
textPaneNames.setFont(font1);
textPaneBody.setFont(font1);
} else if (item == "Traditional") {
textPaneNames.setFont(font2);
textPaneBody.setFont(font2);
} else if (item == "Modern") {
textPaneNames.setFont(font3);
textPaneBody.setFont(font3);
} else if (item == "Crazy") {
textPaneNames.setFont(font4);
textPaneBody.setFont(font4);
}
}
});
comboBox.setModel(
new DefaultComboBoxModel(new String[] { "Select", "Whimsical",
"Traditional", "Modern", "Crazy" }));
textPaneNames = new JTextPane();
textPaneNames.setText("FIRST1 LAST1\n&\nFIRST2 LAST2");
GridBagConstraints gbc_textPaneNames = new GridBagConstraints();
gbc_textPaneNames.insets = new Insets(0, 0, 5, 0);
gbc_textPaneNames.fill = GridBagConstraints.HORIZONTAL;
gbc_textPaneNames.gridx = 3;
gbc_textPaneNames.gridy = 0;
contentPane.add(textPaneNames, gbc_textPaneNames);
textPaneBody = new JTextPane();
textPaneBody.setText(
"REQUEST THE HONOR OF YOUR PRESENCE \nAT THEIR WEDDING
CEREMONY\n\nFRIDAY, JANUARY SECOND\nTWO-THOUSAND AND SEVENTEEN\nSIX-THIRTY IN
THE EVENING\n\nADDRESS GOES HERE\n903 ADDRESS LANE\nCITY, STATE\n\n\nRECEPTION
TO FOLLOW");
GridBagConstraints gbc_textPaneBody = new GridBagConstraints();
gbc_textPaneBody.anchor = GridBagConstraints.NORTH;
gbc_textPaneBody.insets = new Insets(0, 0, 5, 0);
gbc_textPaneBody.fill = GridBagConstraints.HORIZONTAL;
gbc_textPaneBody.gridx = 3;
gbc_textPaneBody.gridy = 1;
contentPane.add(textPaneBody, gbc_textPaneBody);
// centers the names and body text
StyledDocument doc = textPaneBody.getStyledDocument();
StyledDocument doc2 = textPaneNames.getStyledDocument();
SimpleAttributeSet center = new SimpleAttributeSet();
StyleConstants.setAlignment(center, StyleConstants.ALIGN_CENTER);
doc.setParagraphAttributes(0, doc.getLength(), center, false);
doc2.setParagraphAttributes(0, doc2.getLength(), center, false);
}
}
//这里是BackgroundPanel.java：
public class BackgroundPanel extends JPanel {
Image image;
public BackgroundPanel()
{
try
{
image = javax.imageio.ImageIO.read(new
java.net.URL(getClass().getResource("/satin.jpg"), "/satin.jpg"));
}
catch (Exception e) { /*handled in paintComponent()*/ }
}
@Override
protected void paintComponent(Graphics g)
{
super.paintComponent(g);
if (image != null)
g.drawImage(image, 0,0,this.getWidth(),this.getHeight(),this);
}
}
答案 0 :(得分：1)
在主{（1）中BackgroundPanel BP = new BackgroundPanel();之后添加此内容：
frame.add(BP);
您需要将组件添加到框架中。否则不会调用paint（）之类的方法。
答案 1 :(得分：1)
public class BackgroundPanel extends JComponent {
//every code you put in this class
}
如果我是正确的话，这应该可以让你这样做
setContentPane(new BackgroundPanel());
如果这不起作用，请告诉我，以便我能提供更好的服务。
修改
再次查看您的代码我认为这是您必须要做的事情
public InvitationCard(){
setContentPane(new BackgroundPanel());
/* then every other code follows,
except the "setContentPane(contentPane)"
you can comment that out
*/
this.add(contentPane);
}
而且你的BackgroundPanel类仍然可以保留JPanel的子类，这样更好
不再需要frame.add(BP);。
由于我现在没有办法运行它，我仍然不知道这是否解决了你的问题...你告诉我
答案 2 :(得分：0)
这可能有点太晚了，但我认为您可能需要将BackgroundPanel不透明布尔值设置为true。
BackgroundPanel BP = new BackgroundPanel();
BP.setOpaque(true);
您可能需要在任何想要拥有＆＃34;背景＆＃34;的区域进行此操作。颜色或图像。