Java實現時鐘

一、核心的表達式

因為需要動態顯示小時的指針、分鐘的指針、秒的指針的位置，所以確認三個指針的角度非常重要；

X：三個指針相交的原點的X坐標；

Y：三個指針相交的原點的Y坐標；

HOUR_LENGTH、MINUTE_LENGTH、SECOND_LENGTH表示時針、分針、秒針的長度；

hour、minute、second表示現在是幾時、幾分、幾秒；

hourLine.x2 = X+HOUR_LENGTH*Math.cos(hour*(Math.PI/6)-Math.PI/2);
hourLine.y2 = Y+HOUR_LENGTH*Math.sin(hour*(Math.PI/6)-Math.PI/2);
minLine.x2 = X+MINUTE_LENGTH*Math.cos(minute*(Math.PI/30)-Math.PI/2);
minLine.y2 = Y+MINUTE_LENGTH*Math.sin(minute*(Math.PI/30)-Math.PI/2);
secondLine.x2 = X+SECOND_LENGTH*Math.cos(second*(Math.PI/30)-Math.PI/2);
secondLine.y2 = Y+SECOND_LENGTH*Math.sin(second*(Math.PI/30)-Math.PI/2);

二、怎樣動態顯示

簡單的說就是每一秒更新一次屏幕，因此用Timer和TimerTask非常符合要求；每一秒刷新一次；

三、代碼

1. package org.Demo00;
3. import java.awt.Graphics;
4. import java.awt.Graphics2D;
5. import java.awt.geom.Ellipse2D;
6. import java.awt.geom.Line2D;
7. import java.util.Calendar;
8. import java.util.GregorianCalendar;
9. import java.util.Timer;
10. import java.util.TimerTask;
12. import javax.swing.JFrame;
13. import javax.swing.JPanel;
15. public class Test5 extends JFrame {
16. MyPanel clockPanel;
17. Ellipse2D.Double e;
18. int x;
19. int y;
20. Line2D.Double hourLine;
21. Line2D.Double minLine;
22. Line2D.Double secondLine;
23. GregorianCalendar calendar;
24. int hour;
25. int minute;
26. int second;
27. public static final int X = 60;
28. public static final int Y = 60;
29. public static final int X_BEGIN = 10;
30. public static final int Y_BEGIN = 10;
31. public static final int RADIAN = 50;
33. public Test5() {
34. setSize(300, 400);
35. clockPanel = new MyPanel();
36. add(clockPanel);
37. Timer t = new Timer();
38. Task task = new Task();
39. t.schedule(task, 0, 1000);
40. }
42. public static void main(String[] args) {
43. Test5 t = new Test5();
44. t.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
45. t.setVisible(true);
47. }
49. class MyPanel extends JPanel {
50. public MyPanel() {
51. e = new Ellipse2D.Double(X_BEGIN, Y_BEGIN, 100, 100);
52. hourLine = new Line2D.Double(X, Y, X, Y);
53. minLine = new Line2D.Double(X, Y, X, Y);
54. secondLine = new Line2D.Double(X, Y, X, Y);
55. }
57. public void paintComponent(Graphics g) {
58. super.paintComponent(g);
59. Graphics2D g2 = (Graphics2D) g;
60. g2.drawString("12", 55, 25);
61. g2.drawString("6", 55, 105);
62. g2.drawString("9", 15, 65);
63. g2.drawString("3", 100, 65);
64. g2.draw(e);
65. g2.draw(hourLine);
66. g2.draw(minLine);
67. g2.draw(secondLine);
68. }
69. }
71. class Task extends TimerTask {
72. public void run() {
73. calendar = new GregorianCalendar();
74. hour = calendar.get(Calendar.HOUR);
75. minute = calendar.get(Calendar.MINUTE);
76. second = calendar.get(Calendar.SECOND);
77. hourLine.x2 = X + 40 * Math.cos(hour * (Math.PI / 6) - Math.PI / 2);
78. hourLine.y2 = Y + 40 * Math.sin(hour * (Math.PI / 6) - Math.PI / 2);
79. minLine.x2 = X + 45
80. * Math.cos(minute * (Math.PI / 30) - Math.PI / 2);
81. minLine.y2 = Y + 45
82. * Math.sin(minute * (Math.PI / 30) - Math.PI / 2);
83. secondLine.x2 = X + 50
84. * Math.cos(second * (Math.PI / 30) - Math.PI / 2);
85. secondLine.y2 = Y + 50
86. * Math.sin(second * (Math.PI / 30) - Math.PI / 2);
87. repaint();
88. }
89. }
91. }