这是我的错误
Note: Question2. java uses unchecked or unsafe operations.
Note: Recompile with -Xlint : unchecked for details.
这是我的代码：
import javax.swing.*;
import javax.swing.border.TitledBorder;
import java.awt.*;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
public class Question2 extends JFrame implements ActionListener {
//Declare a panel for displaying message
private MessagePanel messagePanel;
// Declare two buttons to move the message left and right
private JButton jbtLeft, jbtRight;
// Declare Combo Box,radioButtons,CheckBox, TextField, Interval
private JTextField jtfNewMessage = new JTextField(8);
private JComboBox jcboInterval = new JComboBox();
private JRadioButton jrbRed = new JRadioButton("Red");
private JRadioButton jrbGreen = new JRadioButton("Green");
private JRadioButton jrbBlue = new JRadioButton("Blue");
private JCheckBox jchkCentered = new JCheckBox("Center");
private JCheckBox jchkBold = new JCheckBox("Bold");
private JCheckBox jchkItalic = new JCheckBox("Italic");
// Declare the Font name, Font style, Font size
private String fontName = "SansSerif";
private int fontStyle = Font.PLAIN;
private int fontSize = 12;
/** Default constructor */
public Question2() {
setTitle("Question2");
// Create a MessagePanel instance and set colors
messagePanel = new MessagePanel("Welcome to Java");
messagePanel.setBackground(Color.white);
// Create Panel jpButtons to hold two Buttons "<=" and "right =>"
JPanel jpButtons = new JPanel();
jpButtons.setLayout(new FlowLayout());
jpButtons.add(jbtLeft = new JButton());
jpButtons.add(jbtRight = new JButton());
// Set button text
jbtLeft.setText("<=");
jbtRight.setText("=>");
// Set keyboard mnemonics
jbtLeft.setMnemonic('L');
jbtRight.setMnemonic('R');
// Set icons
//jbtLeft.setIcon(new ImageIcon("image/left.gif"));
//jbtRight.setIcon(new ImageIcon("image/right.gif"));
// Set toolTipText on the "<=" and "=>" buttons
jbtLeft.setToolTipText("Move message to left");
jbtRight.setToolTipText("Move message to right");
// Place panels in the frame
getContentPane().setLayout(new BorderLayout());
getContentPane().add(messagePanel, BorderLayout.CENTER);
getContentPane().add(jpButtons, BorderLayout.SOUTH);
// Register listeners with the buttons
jbtLeft.addActionListener(this);
jbtRight.addActionListener(this);
/** 1.Add a text field labeled “New Message.\
* Upon typing a new message in the text field and pressing the Enter
* key, the new message is displayed in the message panel.
*/
jpButtons.add(new JLabel("Enter a new message"));
jpButtons.add(jtfNewMessage);
jtfNewMessage.addActionListener(this);
/** 2.Add a combo box label “Interval\uFFFD that enables the user to select
* new interval for moving the message. The selection values range from
* 10 to 100 with interval 5. The user can also type a new
* interval in the combo box.
*/
jpButtons.add(new JLabel("Select an interval"));
jpButtons.add(jcboInterval);
for (int interval = 5; interval <= 100; interval += 5)
jcboInterval.addItem(interval + "");
jcboInterval.addActionListener(this);
/**
* 3.Add three radio buttons that enable the user to select the foreground
* color for the message as Red, Green, and Blue.
*/
JPanel panel = new JPanel();
getContentPane().add(panel, BorderLayout.NORTH);
panel.add(jrbRed);
panel.add(jrbGreen);
panel.add(jrbBlue);
ButtonGroup btg = new ButtonGroup();
btg.add(jrbRed);
btg.add(jrbGreen);
btg.add(jrbBlue);
jrbRed.addActionListener(this);
jrbGreen.addActionListener(this);
jrbBlue.addActionListener(this);
/**
* 4.Add three check boxes that enable the user to center the message
* and display it in italic or bold.
*/
panel.add(jchkCentered);
panel.add(jchkBold);
panel.add(jchkItalic);
jchkCentered.addActionListener(this);
jchkBold.addActionListener(this);
jchkItalic.addActionListener(this);
/**
* 5.Add a border titled Message Panel on the message panel.
*/
messagePanel.setBorder(new TitledBorder("Message Panel"));
jpButtons.setBorder(new TitledBorder("South Panel"));
panel.setBorder(new TitledBorder("North Panel"));
this.setCursor(new Cursor(Cursor.CROSSHAIR_CURSOR));
}
/** Main method */
public static void main(String[] args) {
Question2 frame = new Question2();
frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
frame.setSize(520, 200);
frame.setVisible(true);
}
/** Handle button events */
public void actionPerformed(ActionEvent e) {
if (e.getSource() == jbtLeft) {
messagePanel.moveLeft();
messagePanel.repaint();
}
else if (e.getSource() == jbtRight) {
messagePanel.moveRight();
messagePanel.repaint();
}
else if (e.getSource() == jtfNewMessage) {
messagePanel.setMessage(jtfNewMessage.getText());
messagePanel.repaint();
}
else if (e.getSource() == jcboInterval) {
messagePanel.setInterval(
Integer.parseInt((String)(jcboInterval.getSelectedItem())));
messagePanel.repaint();
}
else if (e.getSource() == jrbRed) {
messagePanel.setForeground(Color.red);
}
else if (e.getSource() == jrbGreen) {
messagePanel.setForeground(Color.green);
}
else if (e.getSource() == jrbBlue) {
messagePanel.setForeground(Color.blue);
}
else if (e.getSource() == jchkCentered) {
if (jchkCentered.isSelected())
messagePanel.setCentered(true);
else
messagePanel.setCentered(false);
messagePanel.repaint();
}
else if ((e.getSource() == jchkBold) ||
(e.getSource() == jchkItalic)) {
fontStyle = Font.PLAIN;
// Determine a font style
if (jchkBold.isSelected())
fontStyle = fontStyle + Font.BOLD;
if (jchkItalic.isSelected())
fontStyle = fontStyle + Font.ITALIC;
// Set font for the message
messagePanel.setFont(new Font(fontName, fontStyle, fontSize));
}
}
public class MessagePanel extends JPanel {
private String message = "Welcome to Java";
private int xCoordinate = 206; //x coordinate where message is displayed
private int yCoordinate = 29; //y coordinate where message is displayed
private boolean centered;//indicate whether message is displayed in the
center
private int interval = 10; // interval for moving message left/right
public MessagePanel() {
}
public MessagePanel(String message) {
this.message = message;
}
public String getMessage() {
return message;
}
public void setMessage(String message) {
this.message = message;
repaint();
}
public int getXCoordinate() {
return xCoordinate;
}
public void setXCoordinate(int x) {
xCoordinate = x;
}
public int getYCoordinate() {
return yCoordinate;
}
public void setYCoordinate(int y) {
yCoordinate = y;
}
public boolean isCentered() {
return centered;
}
public void setCentered(boolean centered) {
this.centered = centered;
repaint();
}
public int getInterval() {
return interval;
}
public void setInterval(int interval) {
this.interval = interval;
repaint();
}
protected void paintComponent(Graphics g) {
super.paintComponent(g);
if (centered) {
FontMetrics fm = g.getFontMetrics();
// find the center location to display
int stringWidth = fm.stringWidth(message);
int stringAscent = fm.getAscent();
// get the position of the leftmost character in the baseline
xCoordinate = getWidth() / 2 - stringWidth / 2;
yCoordinate = getHeight() / 2 - stringAscent / 2;
}
g.drawString(message, xCoordinate, yCoordinate);
}
public void moveLeft() {
xCoordinate -= interval;
repaint();
}
public void moveRight() {
xCoordinate += interval;
repaint();
}
//@override
public Dimension getPreferredSize() {
return new Dimension(200, 30);
}
}
}
我在同一个错误中检查了六个帖子，但我不能
弄清楚出了什么问题。
创建了许多不同的文件，但我反复得到相同的错误。
在那里识别我的错误，这是GUI enter code here
答案 0 :(得分：2)
因为你的开合括号{和}是混乱的。
public class MessagePanel extends JPanel {
这是在方法内部，因此不起作用。在它之前添加一个}。在文件的末尾，您还需要额外的}。
我建议将每个类放在自己的文件中。这是最明确的方式，特别是初学者。
你有两个重复的方法（moveLeft，moveRight）。你应该检查你的变量：
jbtleft与jbtLeft