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HTML5 application clock and html5 clock

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HTML5 application clock and html5 clock

Using the Canvas API of HTML5, we can achieve unexpected animation effects. Before we wanted to place a clock on the webpage, we had to use flash tools to create a clock and write complex JavaScript code, and load it to the page. With the advent of HTML5, we can directly use the canvas tag on the page and use javascript to complete a beautiful clock.





Today, we will use HTML5 to create a clock with pointers moving around.

HTML

We only need to place a canvas label in html: # clock. The width and height are both 400px.

[Html]View plaincopy
  1. <! Doctype html>
  2. <Html>
  3. <Head>
  4. <Meta charset = "UTF-8">
  5. <Title> HTML5 application clock </title>
  6. </Head>
  8. <Body>
  9. <Canvas id = "clock" width = "400" height = "400"> </canvas>
  10. </Body>
  11. </Html>


Javascript

Let's get the current time first: including the hour, minute, and second. Make sure that the pointer position is located when the page is opened, and the dot coordinates and second angle variables are defined.

[Js]View plaincopy
  1. Var time = new Date ();
  2. Var h = time. getHours (); // time
  3. Var m = time. getMinutes (); // minute
  4. Var s = time. getSeconds (); // second
  5. H = h> 12? (H-12) * 5 + parseInt (m/12): h * 5 + parseInt (m/12); // hour initial position
  6. Var x = 200, y = 200, sAngle = 0; // x y origin second point angle variable


Next, we use canvas to draw the clock. We write a function draw () to draw a scale and execute this function once. Then, the second needle moves around 1/60 degrees of arc clockwise.

First, obtain the canvas Drawing Object and draw the clock scale. We divide the clock (circle) into 12 scales, that is, each scale represents an hour, of course, you can also divide it into 60 scales, so that each scale represents 1 minute.

[Js]View plaincopy
  1. Function draw (){
  2. Var c = document. getElementById ("clock ");
  3. Var ctx = c. getContext ("2d"); // obtain the Drawing Object
  4. Ctx. clearRect (, c. width, c. height); // clear the last drawing
  5. S ++; // seconds
  7. Ctx. fillStyle = '# fff' // fill in the white background color
  8. Ctx. fillRect (, c. width, c. height); // you can specify the canvas area.
  10. Ctx. save (); // save the current drawing status
  12. // Time scale
  13. For (var I = 0; I <12; I ++) {// divide 12 scales
  14. Var angle = (Math. PI * 2)/12; // obtain the radians of each scale
  15. Ctx. beginPath (); // start painting
  16. Ctx. font = "12px Arial"; // set the font
  17. If (I = 0 | I = 3 | I = 6 | I = 9) {// when pointing to 0 (12 points)
  18. Ctx. fillStyle = "red"; // The scale is red.
  19. Radius = 4; // The scale radius is 4px long.
  20. } Else {
  21. Ctx. fillStyle = "blue"; // The scale is blue.
  22. Radius = 3; // The scale radius is 3px.
  23. }
  25. Ctx. arc (x, y-100, radius, 0, Math. PI * 2, true); // circle as scale
  26. Ctx. fill (); // fill path
  27. Transform (ctx, x, y, angle, true); // scale Distribution
  28. }
  29. Ctx. restore (); // restore the status of the last saved drawing
  30. ...
  31. }


According to the above code, you can draw a dial with a scale as the clock. Next, we will continue to write the rotation of the hour, minute, and second pointer in the draw () function.

[Js]View plaincopy
  1. Function draw (){
  2. ...
  3. SAngle = (Math. PI * 2)/60 * s; // Second Degree
  4. // Clockwise rotation
  5. Ctx. save ();
  6. Ctx. strokeStyle = "red ";
  7. Ctx. lineWidth = 3;
  8. Transform (ctx, x, y, (Math. PI * 2)/60 * h );
  9. Sj (ctx, x, y, Y-40 );
  10. Ctx. restore ();
  12. // Split the needle to rotate
  13. Ctx. save ();
  14. Ctx. strokeStyle = "blue ";
  15. Ctx. lineWidth = 2;
  16. Transform (ctx, x, y, (Math. PI * 2)/60 * m );
  17. Sj (ctx, x, y, y-68 );
  18. Ctx. restore ();
  20. // Seconds
  21. Ctx. save ();
  22. Ctx. strokeStyle = "#000 ";
  23. Transform (ctx, x, y, sAngle );
  24. Sj (ctx, x, y, y-80 );
  25. Ctx. restore ();
  27. // Data sorting
  28. If (s % 60 = 0 ){
  29. SAngle = 0, s = 0, m ++;
  30. If (m % 12 = 0) {// rotate once every 12 minutes
  31. If (m! = 0) h ++;
  32. If (m % 60 = 0) m = 0;
  33. }
  34. If (h % 60 = 0) h = 0;
  35. }
  36. }


For each call to draw (), we set different fill colors and pointer thicknesses for the hour, minute, and second pins, draw pointers, and rotate pointer positions based on radians. In this example, we call the custom function trans () and pointer ().

The pointer () function is used to draw pointers. Ctx indicates the canvas object, x, y indicates the dot coordinate, and z indicates the position of the pointer header.

[Js]View plaincopy
  1. Function pointer (ctx, x, y, z ){
  2. Ctx. beginPath ();
  3. Ctx. moveTo (x, y );
  4. Ctx. lineTo (x, z );
  5. Ctx. stroke ();
  6. Ctx. fill ();
  7. }


The transform () function is used to rotate the pointer. Ctx indicates the canvas object, x, y indicates the dot coordinate, and angle indicates the rotation angle.

[Js]View plaincopy
  1. Function trans (ctx, x, y, angle ){
  2. Ctx. transform (Math. cos (angle), Math. sin (angle ),
  3. -Math. sin (angle), Math. cos (angle ),
  4. X * (1-Math.cos (angle) + x * Math. sin (angle ),
  5. Y * (1-Math.cos (angle)-y * Math. sin (angle ))
  6. }


Finally, we set to execute draw () every 1 second (that is, 1000 milliseconds ().

[Js]View plaincopy
    1. SetInterval ("draw ()", 1000 );

This article is an English version of an article which is originally in the Chinese language on aliyun.com and is provided for information purposes only. This website makes no representation or warranty of any kind, either expressed or implied, as to the accuracy, completeness ownership or reliability of the article or any translations thereof. If you have any concerns or complaints relating to the article, please send an email, providing a detailed description of the concern or complaint, to info-contact@alibabacloud.com. A staff member will contact you within 5 working days. Once verified, infringing content will be removed immediately.

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