【JAVA语言程序设计基础篇】--图形--练习绘制时钟

package chapter15;import java.awt.*;import java.util.Calendar;import java.util.GregorianCalendar;import javax.swing.*;@SuppressWarnings("serial")public class DisplayClock extends JFrame{public DisplayClock(){StillClock clock = new StillClock();MessagePanel messagePanel = new MessagePanel(clock.getHour()+":"+clock.getMinute()+":"+clock.getSecond());messagePanel.setCentered(true);messagePanel.setForeground(Color.blue);messagePanel.setFont(new Font("Courier",Font.BOLD,16));add(clock);add(messagePanel,BorderLayout.SOUTH);}public static void main(String[] args) {DisplayClock frame = new DisplayClock();frame.setVisible(true);frame.setSize(300, 350);frame.setLocationRelativeTo(null);frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);frame.setTitle("hello java");}}@SuppressWarnings("serial")class StillClock extends JPanel {private int hour;private int minute;private int second;/** Construct a default clock with the current time */public StillClock() {setCurrentTime();}/** Construct a clock with specified hour, minute, and second */public StillClock(int hour, int minute, int second) {this.hour = hour;this.minute = minute;this.second = second;}/** Return hour */public int getHour() {return hour;}/** Set a new hour */public void setHour(int hour) {this.hour = hour;repaint();}/** Return minute */public int getMinute() {return minute;}/** Set a new minute */public void setMinute(int minute) {this.minute = minute;repaint();}/** Return second */public int getSecond() {return second;}/** Set a new second */public void setSecond(int second) {this.second = second;repaint();}/** Draw the clock */protected void paintComponent(Graphics g) {super.paintComponent(g);// Initialize clock parametersint clockRadius = (int) (Math.min(getWidth(), getHeight()) * 0.8 * 0.5);int xCenter = getWidth() / 2;int yCenter = getHeight() / 2;// Draw circleg.setColor(Color.black);g.drawOval(xCenter - clockRadius, yCenter - clockRadius,2 * clockRadius, 2 * clockRadius);g.drawString("12", xCenter - 5, yCenter - clockRadius + 12);g.drawString("9", xCenter - clockRadius + 3, yCenter + 5);g.drawString("3", xCenter + clockRadius - 10, yCenter + 3);g.drawString("6", xCenter - 3, yCenter + clockRadius - 3);// Draw second handint sLength = (int) (clockRadius * 0.8);int xSecond = (int) (xCenter + sLength* Math.sin(second * (2 * Math.PI / 60)));int ySecond = (int) (yCenter - sLength* Math.cos(second * (2 * Math.PI / 60)));g.setColor(Color.red);g.drawLine(xCenter, yCenter, xSecond, ySecond);// Draw minute handint mLength = (int) (clockRadius * 0.65);int xMinute = (int) (xCenter + mLength* Math.sin(minute * (2 * Math.PI / 60)));int yMinute = (int) (yCenter - mLength* Math.cos(minute * (2 * Math.PI / 60)));g.setColor(Color.blue);g.drawLine(xCenter, yCenter, xMinute, yMinute);// Draw hour handint hLength = (int) (clockRadius * 0.5);int xHour = (int) (xCenter + hLength* Math.sin((hour % 12 + minute / 60.0) * (2 * Math.PI / 12)));int yHour = (int) (yCenter - hLength* Math.cos((hour % 12 + minute / 60.0) * (2 * Math.PI / 12)));g.setColor(Color.BLACK);g.drawLine(xCenter, yCenter, xHour, yHour);}public void setCurrentTime() {// Construct a calendar for the current date and timeCalendar calendar = new GregorianCalendar();// Set current hour, minute and secondthis.hour = calendar.get(Calendar.HOUR_OF_DAY);this.minute = calendar.get(Calendar.MINUTE);this.second = calendar.get(Calendar.SECOND);}public Dimension getPreferredSize() {return new Dimension(200, 200);}}@SuppressWarnings("serial")class MessagePanel extends JPanel {  /** The message to be displayed */  private String message = "Welcome to Java";  /** The x coordinate where the message is displayed */  private int xCoordinate = 20;  /** The y coordinate where the message is displayed */  private int yCoordinate = 20;  /** Indicate whether the message is displayed in the center */  private boolean centered;  /** The interval for moving the message horizontally    * and vertically */  private int interval = 10;  /** Construct with default properties */  public MessagePanel() {  }  /** Construct a message panel with a specified message */  public MessagePanel(String message) {    this.message = message;  }  /** Return message */  public String getMessage() {    return message;  }  /** Set a new message */  public void setMessage(String message) {    this.message = message;    repaint();  }  /** Return xCoordinator */  public int getXCoordinate() {    return xCoordinate;  }  /** Set a new xCoordinator */  public void setXCoordinate(int x) {    this.xCoordinate = x;    repaint();  }  /** Return yCoordinator */  public int getYCoordinate() {    return yCoordinate;  }  /** Set a new yCoordinator */  public void setYCoordinate(int y) {    this.yCoordinate = y;    repaint();  }  /** Return centered */  public boolean isCentered() {    return centered;  }  /** Set a new centered */  public void setCentered(boolean centered) {    this.centered = centered;    repaint();  }  /** Return interval */  public int getInterval() {    return interval;  }  /** Set a new interval */  public void setInterval(int interval) {    this.interval = interval;    repaint();  }  /** Paint the message */  protected void paintComponent(Graphics g) {    super.paintComponent(g);    if (centered) {      // Get font metrics for the current font      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);  }  /** Move the message left */  public void moveLeft() {    xCoordinate -= interval;    repaint();  }  /** Move the message right */  public void moveRight() {    xCoordinate += interval;    repaint();  }  /** Move the message up */  public void moveUp() {    yCoordinate -= interval;    repaint();  }  /** Move the message down */  public void moveDown() {    yCoordinate += interval;    repaint();  }  /** Override get method for preferredSize */  public Dimension getPreferredSize() {    return new Dimension(200, 30);  }}