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  1. 1. Introduction to HTML5 Jeanine Meyer Purchase College/SUNY
  2. 2. Introductions• Jeanine Meyer – Purchase College/SUNY: Math/CS & New Media. Prior: IBM Research (robotics, manufacturing research, educational grants), Pace University. – 5 books: latest is The Essential Guide to HTML5: Using Games to learn HTML5 & JavaScript
  3. 3. Background• HTML5 is the latest/soon to be version of – HyperText Markup Language (HTML): text with tags for content – JavaScript: scripting/programming language for interactivity, dynamic presentation – Cascading Style Sheets: formatting• Many new features, for support of semantic web, dynamic/interactive websites• CAUTION: definition not official.• Browser support evolving.• Do ask/remind me to say: what are my names versus built-in parts of HTML5.
  4. 4. New features include:• Semantic elements: header, footer, section, article, others.• canvas for drawing – paths of rectangles, arcs, lines, images – mouse events• localStorage (variation of cookies)• audio & video elements – including drawing video on canvas
  5. 5. This Tutorial• Build Favorite sites – review HTML structure, new elements)• Build Drawings – draw rectangles, arcs, lines on canvas• Build Coin toss – event handling, draw text and images on canvas• Find video clips & convert. – Add video to favorite sites or make it stand-alone.• Build Bouncing Video – draw video, create mask, timed event• Build geolocation application, including Google Maps API app and localStorage• Preview Essential Guide to HTML5
  6. 6. Tools• TextPad or TextWrangler or NotePad – Dreamweaver okay but it does cost.• Compatible browser – Firefox: works for all examples, including masked video and geolocation – Chrome and Safari work for most examples – IE9 being tested now• Miro Converter
  7. 7. HTML review• Elements consist of opening tag, contents of the element and closing tag.• Tags have attributes.<a href="nextpage.html">NEXT </a>• Some elements/tags are singletons<img src="logo.gif" width="100"/>• Document Object Model (DOM) defines relationships, attributes & methods of objects.
  8. 8. First webpage: Favorite Sites• Annotated list of favorite sites• Need to determine URLs for links, images, brief text.• header and article elements• style element (CSS) for formatting – critical for header and article. Also use it for images• script element: single statement to insert date.•
  9. 9. screen shot,not live html
  10. 10. Advice• HTML does not recognize white space.• You need to make spacing and line breaks explicit.• For your readability, put line breaks and spaces.• My objective often is to squeeze things in one slide. This isnt your objective!
  11. 11. HTML template<!DOCTYPE html><html lang="en"><head> <title></title> <meta charset="utf-8"></head><body> </body></html>
  12. 12. Favorite Sites• overview for this example:<!DOCTYPE html><html lang="en"> <head> <title> </title> <meta charset="UTF-8"> <style> </style> // for header and article and img <script> </script> </head> <body> content: header, article for each site </body> </html>
  13. 13. <style>header {font-family:Georgia,"Times New Roman",serif; text-align:center; font-size:30px; display:block; }article { text-align:left; font-size:20px; margin:20px; display:block; font-family:"Century","Tahoma", sans- serif; }img {display:block;}</style><script>document.write(Date());</script> </head>
  14. 14. <body><header>Favorite Sites </header><article>My Academic website, <a href=" meyer"></a>is where I put information about my courses, along with publications and other activities.<img src="purchase_logo_sm.gif" width="200"/> </article><article>My daughter, Aviva, is active in the <a href="">Stolen Chair Theater company.</a> The next production involves Victorian photo-collage.<img src="CSTlogo.jpg" width="100"/></article> <body> </html>
  15. 15. Comments• Remember: spaces, line breaks need to be inserted explicitly• My first attempt was to use <br/> to force images to their own line. I changed to using a style to keep formatting in the <style> section. – need not be so pure!• GO! - get information, look up other CSS, ask!
  16. 16. 2 set of projects: Drawing nd• canvas element• Use code to define a so-called context. Methods of this object do the work!• Screen geometry: upper left corner is origin.• Colors defined by red-green-blue values or a small set of named colors, – – will show hexadecimal example later.• stroke versus fill• draw Rectangles•
  17. 17. 500,0,default 0,0, default color, 10 color,20 by 20, fill by 10, stroke0,300,green,30 by 30, rgb(200,0,100)stroke 500,300, 50 by 50, fill
  18. 18. <!DOCTYPE html><html lang="en"><head><title>Four rectangles</title><meta charset="UTF-8"><script>var ctx;function init() { ctx = document.getElementById(canvas).getContext(2d); ctx.lineWidth = 2; ctx.strokeRect(0,0,10,10); ctx.fillRect(500,0,20,20); ctx.strokeStyle = "green"; ctx.fillStyle = "rgb(200,0,100)"; ctx.strokeRect(0,300,30,30); ctx.fillRect(500,300,50,50); }</script> </head><body onLoad="init();"><canvas id="canvas" width="600" height="400"> Your browser doesnt support the HTML5 element canvas.</canvas> </body> </html>
  19. 19. Errors• JavaScript is scripting language: interpret statements at execution time. – NOT compiled, with error messages• Semantic errors (errors of meaning) are more difficult to detect and fix!• Syntactic errors are errors of form, analogous to grammatical errors – FireFox Tools/Error Console can help • Most common: bad bracketing • ctx.fillStyle("rgb(200,0,100)"); fillStyle is attribute,not method
  20. 20. Comments• The drawing is done in the init function which is called when the body element is loaded. The canvas element with id="canvas" does not exist until the body is loaded.• Default color is black. Red green blue values each are 0 to 255 (8 bits of intensity). The strokeStyle and the fillStyle are attributes, not methods.• GO: experiment with colors (by name) and rgb (note the quotation marks) and location and width and height.
  21. 21. More comments• Drawings are …paint on the canvas.• These rectangles are not objects to be moved or referenced later.• Use ctx.clearRect method to erase.• Need to do calculations to detect hits. – See memory game in book.• Alternative is dynamic placement of html markup – See quiz, hangman.
  22. 22. Next drawing• Paths created with arcs and line segments• Arcs are portions of circles, created using radians in place of degrees. Math.PI is available for use. A complete circle can be drawn from 0 to 2*Math.PI or –Math.PI to Math.PI, etc.• Arcs can be stroke or fill.• workshop/wkshopsmile.html• workshop/wkshopfrown.html
  23. 23. Angles PI*3/2PI 0 (=2*PI) .20 * PI PI/4.80*PI true means PI/2 counter- clockwise!
  24. 24. arcs• ctx.arc (x of center, y of center, radius, starting angle, finishing angle, true for counter-clockwise)• No drawing (ink) at the center! This is important when connecting arcs and lines.• EXPERIMENT
  25. 25. 4 distinctpaths, eachmade up of 1arc.Default, "red"and "brown"
  26. 26. Strategy• Use variables with some variable values defined in terms of others.• Circle face and two eyes. Smile is (partial) arc. Brown eyes and red smile.• body element same as before. – You can add the code for this to your rectangles drawing.
  27. 27. var ctx;var headx = 100; //center of face x coord.var heady = 200; // center of face y coord.var headrad = 50; //radius of facevar smileoffsetx=0; //smile center x is same as facevar smileoffsety = 15; //smile center y further downvar smilerad=20; // smile radiusvar eyeoffsety = -10; //eyes up from centervar lefteyeoffsetx = -15; //left eyevar righteyeoffsetx = -lefteyeoffsetx; //rightvar eyerad = 8; // eye radius
  28. 28. function init() { ctx = document.getElementById(canvas).ge tContext(2d); ctx.lineWidth = 5; ctx.beginPath(); ctx.arc(headx,heady,headrad,0,2*Math .PI,true); ctx.closePath(); ctx.stroke(); …
  29. 29. ctx.strokeStyle = "red";ctx.beginPath();ctx.arc(headx+smileoffsetx,heady+smileoffsety, smilerad,.80*Math.PI,.20*Math.PI,true);ctx.stroke();ctx.fillStyle = "brown"; ctx.beginPath();ctx.arc(headx+lefteyeoffsetx,heady+eyeoffsety, eyerad, 0,2*Math.PI,true);ctx.fill();ctx.beginPath(); ctx.arc(headx+righteyeoffsetx,heady+eyeoffset y,eyerad,0,2*Math.PI,true); ctx.fill(); }
  30. 30. Comments• The fill and stroke calls close the path.• Also, can close a path with closePath()• Using variables makes code more flexible and easier to see relationships.• GO: draw arcs, changing colors, sizes, etc.• NOTE: can draw non-circular ovals using transformations: scale. Check out the hangman game in book!
  31. 31. Next drawing: star• For drawing lines (and arcs), think of moving a pencil versus drawing (preparing to draw) a line segment – nothing is drawn until the stroke or fill• Use an array with coordinates for 5 points• Use an array to hold names of 3 colors• button element• html5workshop/wkshopdrawingstars.html
  32. 32. opening screen
  33. 33. after 1 press of button st
  34. 34. after next press
  35. 35. after next press
  36. 36. show body first<body onLoad="init();"><canvas id="canvas" width="600" height="400">Your browser doesnt support the HTML5 element canvas.</canvas><button onClick="makestar();">Make Star </button></body></html>
  37. 37. variables (in script element)var ctx;var pts=[//5 points for star: rough drawing [100,35], [60,10], [20,35], [35,100], [85,100] ];var colors=["red","white","blue"]; //used in successionvar c=0; // points to next color
  38. 38. variables (in script element)var ctx;var pts=[ //5 points for star: rough drawing [100,35], [60,10], [20,35], [35,100], [85,100] ];var colors=["red","white","blue"]; //used in successionvar c=0; // points to next color
  39. 39. variables (in script element)var ctx;var pts=[ //5 points for star: rough drawing [100,35], [60,10], [20,35], [35,100], [85,100] ];var colors=["red","white","blue"];//used in successionvar c=0; // points to next color
  40. 40. variables (in script element)var ctx;var pts=[ //5 points for star: rough drawing [100,35], [60,10], [20,35], [35,100], [85,100] ];var colors=["red","white","blue"];//used in successionvar c=0; // points to next color
  41. 41. variables (in script element)var ctx;var pts=[ //5 points for star: rough drawing [100,35], [60,10], [20,35], [35,100], [85,100] ];var colors=["red","white","blue"]; //used in successionvar c=0; // points to next color
  42. 42. function init() { ctx =document.getElementById(canvas).getContext(2d); }function makestar() { ctx.clearRect(0,0,600,400); ctx.fillStyle=colors[c]; c = c +1;// can reduce to one line using colors[c++] c = (c<3)?c:0; ctx.beginPath(); ctx.moveTo(pts[0][0],pts[0][1]); ctx.lineTo(pts[3][0],pts[3][1]); ctx.lineTo(pts[1][0],pts[1][1]); ctx.lineTo(pts[4][0],pts[4][1]); ctx.lineTo(pts[2][0],pts[2][1]); ctx.lineTo(pts[0][0],pts[0][1]); ctx.stroke();//outline (necessary for white star! ctx.fill(); }
  43. 43. Comments• Your assignment: do something with a button. It does not have to be a star.• But do use moveTo and lineTo.• You can combine with rectangles (separate from paths) and arcs (can combine with lines).• Try stroke and fill• Can include multiple moveTo – think of picking up your pen and moving to a new spot on the paper/canvas.
  44. 44. Fancier stars• Code to draw star more precisely• Position each star randomly on canvas. – Add star with each button press• Increase number of colors. – – improve coding for robustness• html5workshop/wkshopprecisestars.html
  45. 45. after many presses
  46. 46. Strategy• reuse code for makestar, with modification – remove clearRect method – add a call to buildstar that re-creates the pts array• add items to colors array – remove 3 from the code!• position, size, and rotation of star created using calls to Math.random.
  47. 47. variablesvar ctx;var angle = 2*Math.PI/5;var pts=[ ];var colors=["red","white","blue","p urple","yellow","teal"];var c=0;
  48. 48. function makestar() {buildstar();ctx.fillStyle=colors[c++];c = (c<colors.length)?c:0;ctx.beginPath();ctx.moveTo(pts[0][0],pts[0][1]);ctx.lineTo(pts[3][0],pts[3][1]);ctx.lineTo(pts[1][0],pts[1][1]);ctx.lineTo(pts[4][0],pts[4][1]);ctx.lineTo(pts[2][0],pts[2][1]);ctx.lineTo(pts[0][0],pts[0][1]);ctx.stroke();ctx.fill();}
  49. 49. function buildstar() { pts = []; var x=500*Math.random(); //all these arbitrary var y = 300*Math.random(); var r=50*Math.random(); var sangle = Math.random()*angle; for(var i=0;i<5;i++) { var a = i*angle + sangle; var px = x+r*Math.cos(a); var py = y-r*Math.sin(a); pts.push([px,py]); }}
  50. 50. Comments• Lesson of these examples is that drawings are dynamic! – can be done under specific circumstances in a program – using different values• Do this if there is time. Consider changing – names of colors – constants – draw something instead of or in addition to the star – ?
  51. 51. Next: coin flip• Draw image from image file of head or tail on canvas where player clicks mouse – event handling: listen for mouse click – draw image made from external file• Draw text (with directions) on canvas• html5workshop/wkshopcoinflip.html
  52. 52. opening screen
  53. 53. after mouse click
  54. 54. Strategy• Need to locate/identify file address for images – can be in same folder (use relative address) or use full URL• Image objects with src attribute• font set for context (ctx)• event handling done for canvas element NOT context. Sets up call to function that has 1 parameter• Does require browser specific code to get mouse coordinates. (Sigh….) – use technique of checking for presence of attribute
  55. 55. Strategy, cont.• Fonts are from what is available on the client computer.• draw outline (strokeRect) to show player where canvas is.• Alternative to color names or rgb is hexadecimal. – use PhotoShop or Paint Shop Pro• Note that my code makes adjustment to put middle of image where mouse was clicked.
  56. 56. variablesvar ctx;var canvas1;var head = new Image();var tail = new Image();head.src = "head.gif";tail.src = "tail.gif";var coinwidth = 100;var coinheight = 100;
  57. 57. functionsfunction init() { ctx = document.getElementById(canvas).getConte xt(2d); canvas1 = document.getElementById(canvas); canvas1.addEventListener(click,flip,fals e); ctx.font = "italic 20px Accent"; ctx.fillStyle = "#dd00ff"; ctx.strokeRect(0,0,600,400); ctx.fillText("Click on canvas to flip a coin.",10,20);}
  58. 58. function flip(ev) {var mx;var my;ctx.clearRect(0,0,600,400); if ( ev.layerX || ev.layerX == 0) { // Firefox mx= ev.layerX; my = ev.layerY; } else if (ev.offsetX || ev.offsetX == 0) { // Opera mx = ev.offsetX; my = ev.offsetY; } if (Math.random()>.5) { ctx.drawImage(head,mx-50,my- 50,coinwidth,coinheight); } else { ctx.drawImage(tail,mx-50,my- 50,coinwidth,coinheight);}ctx.strokeRect(0,0,600,400);ctx.fillText("Click on canvas to flip a coin.",10,20); }
  59. 59. Comments• You need to acquire two images to represent the coin faces. – download to same folder or use exact, complete address• You can go into Word, or equivalent, to see available fonts. – more in book AND online.• Go!
  60. 60. Background on audio & video• This is native support (no need for plugins), no dependence on YouTube.• Issue: Multiple formats (aka codecs) for each. – Different browsers recognize different formats. – Situation MAY improve: may be standardization. – Good news: the <audio> and <video> elements provide way to reference multiple files and let browser choose (though order does seem to be important).
  61. 61. Audio & video elements<audio autobuffer><source src="crowdohh.ogg" /><source src="crowdohh.mp3" /></audio><video controls="controls"><source src="sfire3.mp4" type=video/mp4; codecs="avc1.42E01E, mp4a.40.2"><source src="sfire3.theora.ogv" type=video/ogg; codecs="theora, vorbis"><source src="sfire3.webmvp8.webm" type="video/webm; codec="vp8, vorbis""> </video>
  62. 62. Our goal now• Find and download video files.• Use Miro Converter to produce other formats.• Put audio into one of existing projects.• Put video into one of existing projects.• Build video bouncing ball.• Look at books rock-paper-scissors for playing specific sounds at specific times.• Look at books quiz for keeping video invisible and playing it only when quiz round complete.
  63. 63. Acquire video• Make your own.• Find on-line. Site lets you specify a URL and choose from the videos to download. – Respect intellectual property!!! – Respect personal privacy (of friends & family, etc.)!!!
  64. 64. Produce all formats• Produce formats for all browsers: –• Download the program.• The original file can be in several different formats, including flv (Flash format, used by YouTube).• Follow directions: should produce the 3 formats: mp4, theora.ogv, webmvp8.webm
  65. 65. Next: Video• Put video element in your favorite sites or something else or ???• Test using Firefox, Chrome and Safari.• PATIENCE!!
  66. 66. Next: Bouncing video• Two versions – move around video element – use drawImage to place video on canvas (works in FireFox) • Doing this makes it easier to draw mask. Otherwise, difficult to position.• "Not quite ready for prime time". Need to put in code to wait until video all downloaded.
  67. 67. Strategy• Use setInterval to invoke [my] drawscene function – re-position video. – Check against [virtual] walls. Apply angle of incidence equal angle of reflection (easy to do) – use strokeRect to draw box• NOTE: the loop attribute did not work, so I set up event handling for video ended event.
  68. 68. Function tableinit Called by action of onLoad in <body>restart … addEventListener in initdrawscene … setInterval in init. This is different in two versionsmoveandcheck Called in drawscene
  69. 69. Bouncing video rectangle• canvas and video distinct elements• html5workshop/videobounce1.html
  70. 70. Video is in motion
  71. 71. Style sectionPositioning and layering (my term).Note: to change z-index by JavaScript, use zIndex.<style>#vid {position:absolute; visibility:hidden; z-index: 0; }#canvas {position:absolute; z- index:10;}</style>
  72. 72. <script type="text/javascript"> var ctx; var cwidth = 900; var cheight = 600; var ballrad = 50; var boxx = 20; var boxy = 30; var boxwidth = 850; var boxheight = 550; var boxboundx = boxwidth+boxx-2*ballrad; var boxboundy = boxheight+boxy-2*ballrad; var inboxboundx = 0; var inboxboundy = 0; var ballx = 50; var bally = 60; var ballvx = 2; var ballvy = 4; var v;
  73. 73. function init(){ ctx = document.getElementById(canvas).getConte xt(2d); v = document.getElementById("vid"); v.addEventListener("ended",restart,false); = ballx; = bally; v.width = 2*ballrad; v.height = 2*ballrad;; = "visible"; setInterval(drawscene,50);}
  74. 74. function restart() { v.currentTime=0;;}
  75. 75. function drawscene(){ ctx.lineWidth = ballrad; ctx.clearRect(boxx,boxy,boxwidth,boxheight ); moveandcheck(); = ballx; = bally; ctx.strokeStyle ="rgb(200,0,50)"; ctx.strokeRect(boxx,boxy,boxwidth,boxheigh t); //box}
  76. 76. function moveandcheck() { var nballx = ballx + ballvx; var nbally = bally +ballvy; if (nballx > boxboundx) { ballvx =-ballvx; nballx = boxboundx; } if (nballx < inboxboundx) { nballx = inboxboundx ballvx = -ballvx; } if (nbally > boxboundy) { nbally = boxboundy; ballvy =-ballvy; } if (nbally < inboxboundy) { nbally = inboxboundy; ballvy = -ballvy; } ballx = nballx; bally = nbally; }
  77. 77. <body onLoad="init();"><video id="vid" loop="loop" preload="auto"><source src="joshuahomerun.mp4" type=video/mp4; codecs="avc1.42E01E, mp4a.40.2"><source src="joshuahomerun.theora.ogv" type=video/ogg; codecs="theora, vorbis"><source src="joshuahomerun.webmvp8.webm" type=video/webm; codec="vp8, vorbis">Your browser does not accept the video tag. </video><canvas id="canvas" width="900" height="600">This browser doesnt support the HTML5 canvas element.</canvas></body>
  78. 78. Bouncing video circle• Works in Firefox.• video used in drawImage.• A mask is created: a box with a hole positioned over the video to produce a circular• html5workshop/videobounce3.html
  79. 79. Video is in motion
  80. 80. <script> var ctx; var cwidth = 900; var cheight = 600; var ballrad = 50; var boxx = 20; var boxy = 30; var boxwidth = 850; var boxheight = 550; var boxboundx = boxwidth+boxx-2*ballrad; var boxboundy = boxheight+boxy-2*ballrad; var inboxboundx = 0; var inboxboundy = 0; var ballx = 50; var bally = 60; var ballvx = 2; var ballvy = 4; var maskrad; var v;
  81. 81. function init(){ ctx = document.getElementById(canvas).getConte xt(2d); v = document.getElementById("vid"); v.addEventListener("ended",restart,false); // because loop doesnt work on FF v.width = v.videoWidth/3; v.height = v.videoHeight/3; videow = v.width; videoh = v.height; maskrad = .4*Math.min(videow,videoh);; setInterval(drawscene,50); }
  82. 82. function restart() { v.currentTime=0;;}
  83. 83. function drawscene(){ ctx.lineWidth = ballrad; ctx.clearRect(0,0,boxwidth+boxx,boxheight+boxy); ctx.fillStyle="rgb(255,255,255)"; //white moveandcheck(); ctx.drawImage(v,ballx+boxx, bally+boxy, v.width,v.height); ctx.beginPath(); ctx.moveTo(ballx+boxx,bally+boxy); ctx.lineTo(ballx+boxx+v.width,bally+boxy); ctx.lineTo(ballx+boxx+v.width,bally+boxy+v.height); ctx.lineTo(ballx+boxx,bally+boxy+v.height); ctx.lineTo(ballx+boxx,bally+boxy);ctx.arc(ballx+boxx+.5*v.width,bally+boxy+.5*v.height,maskr ad,0, Math.PI*2,true); ctx.fill(); //draw white mask on top of video, letting just circle show ctx.strokeStyle ="rgb(200,0,50)"; ctx.strokeRect(boxx,boxy,boxwidth,boxheight); //box}
  84. 84. function moveandcheck() { var nballx = ballx + ballvx; var nbally = bally +ballvy; if (nballx > boxboundx) { ballvx =-ballvx; nballx = boxboundx; } if (nballx < inboxboundx) { nballx = inboxboundx ballvx = -ballvx; } if (nbally > boxboundy) { nbally = boxboundy; ballvy =-ballvy; } if (nbally < inboxboundy) { nbally = inboxboundy; ballvy = -ballvy; } ballx = nballx; bally = nbally; }
  85. 85. <body onLoad="init();"><video id="vid" loop="loop" preload="auto"><source src="joshuahomerun.mp4" type=video/mp4; codecs="avc1.42E01E, mp4a.40.2"><source src="joshuahomerun.theora.ogv" type=video/ogg; codecs="theora, vorbis"><source src="joshuahomerun.webmvp8.webm" type=video/webm; codec="vp8, vorbis">Your browser does not accept the video tag. </video><canvas id="canvas" width="900" height="600">This browser doesnt support the HTML5 canvas element.</canvas></body>
  86. 86. Next: Maps app• Use Google Maps API to bring up map at current location.• Respond to clicking by placing a marker and calculating distance.• Provide way to change to fixed set of locations or the last marker.• workshop/geolocationdistance2.html – need to give permission to Share Location• Works in Chrome and Firefox. Does not work in Safari for Windows.
  87. 87. Opening screen
  88. 88. Brings up ….
  89. 89. After click on map
  90. 90. After choose CUNY
  91. 91. Mapping• Google Maps API (and other applications) defines positions using special latitude/longitude data object• Access to Google Map is created for a place in the HTML document, using specified map options• HTML has a specification for doing geolocation. – navigator.geolocation produces latitude and longitude values
  92. 92. How to get positions?• Google Maps – get to a map • Browser location javascript:void(prompt(,gApplication.getMap().get Center())); OR • Click on green beaker and enable the drop latlng marker – right click then normal click
  93. 93. My program• Tries to use the geolocation• Gives user option to pick base location• User can click on map and find distance from base center.• Can change base to last clicked on position.• General access to Google Maps features.
  94. 94. Basics• if (navigator.geolocation) checks if this object exists. Does NOT cause any errors.if (navigator.geolocation) {navigator.geolocation.getCurrentPosit ion(handler,problemhandler);}• handler when things go okay. problemhandler when there are errors, including user deciding not to share location.
  95. 95. Create/Access Google Maps• map = new google.maps.Map(document.getElementB yId("place"), myOptions); brings up Google Maps in the div with id "place" using the parameters in myOptions.<div id="place" style="width:600px; height:400px"></div> • NOTE: use of % for width and height did not work when <! DOCTYPE html> used.
  96. 96. style, external script<style>header {font-family:Georgia,"Times New Roman",serif; font-size:20px; display:block;}</style><script type="text/javascript" src=" /js?sensor=false"></script><script language="Javascript">
  97. 97. init() codefunction init() {if (navigator.geolocation) {navigator.geolocation.getCurrentPosition(handler,problemhandler);}else { if (document.getElementById("place")) { document.getElementById("place").innerHTML = "Im sorry but geolocation services are not supported by your browser"; document.getElementById("place").style.color = "#FF0000"; } } }
  98. 98. function handler(position) { var mylat = position.coords.latitude; var mylong = position.coords.longitude; makemap(mylat,mylong);}
  99. 99. error handlingfunction problemhandler(prob) { switch(prob.code) { case 1: document.getElementById("place").innerHTML = "User declined to share the location information."; break; case 2: document.getElementById("place").innerHTML = "Errors in getting base location."; break; case 3: document.getElementById("place").innerHTML = "Timeout in getting base location."; } document.getElementById("header").innerHTM L = "Base location needs to be set!"; }
  100. 100. variablesvar listener;var map;var markersArray =[];var blatlng;var myOptions;var locations = [ [35.1494444,-90.0488889, "Memphis, TN"], [41.04796,- 73.70539,"Purchase College/SUNY"], [41.878928, -87.641926,"IIT"] ];
  101. 101. create/access mapfunction makemap(mylat, mylong) { blatlng = new google.maps.LatLng(mylat,mylong);myOptions = { zoom: 14, center: blatlng, mapTypeId: google.maps.MapTypeId.ROADMAP}; map = new google.maps.Map(document.getElementById("p lace"), myOptions); listener = google.maps.event.addListener(map, click, function(event) { checkit(event.latLng);}); }
  102. 102. response to click on mapfunction checkit(clatlng) { var distance = dist(clatlng,blatlng); distance = Math.floor((distance+.005)*100)/100; var distanceString = String(distance)+" miles"; marker = new google.maps.Marker({ position: clatlng, title: distanceString, map: map }); markersArray.push(marker); document.getElementById("answer").innerHTML = "The distance from base to most recent marker is "+String(distance) +" miles."; }
  103. 103. distance functionfunction dist(point1, point2) { //spherical law of cosines //var R = 6371; // km var R = 3959; // miles var lat1 =*Math.PI/180; var lat2 =*Math.PI/180 ; var lon1 = point1.lng()*Math.PI/180; var lon2 = point2.lng()*Math.PI/180;var d = Math.acos(Math.sin(lat1)*Math.sin(lat2) + Math.cos(lat1)*Math.cos(lat2) * Math.cos(lon2-lon1)) * R; return d; }
  104. 104. change base using radio buttonsfunction changebase() { for(var i=0;i<locations.length;i++) { if (document.f.loc[i].checked) { makemap(locations[i] [0],locations[i][1]); document.getElementById("header").innerHTM L = "Base location is "+locations[i][2]; } } return false;}
  105. 105. </script> </head> <body onload="init();"><header id="header">Base location is your current geolocation</header><div id="place" style="width:600px; height:400px"></div><div id="answer"></div>Change base location: <br/><form name="f" onSubmit=" return changebase();"> <input type="radio" name="loc" /> Memphis<br/> <input type="radio" name="loc" /> Purchase College<br/> <input type="radio" name="loc" /> Illinois Institute of Technology<br/><input type="submit" value="CHANGE"></form> </body> </html>
  106. 106. Variation• Geolocation returns accuracy and, maybe, other information, including altitude.• These applications mark the center with a red x and display other information – 5workshop/geolocation.html – 5workshop/geolocationkm.html • Note: accuracy is given in meters in both cases
  107. 107. Critical code• Uses custom image for markervar xmarker = "x1.png";…marker = new google.maps.Marker({ position: blatlng, title: "center", icon: xmarker, map: map });
  108. 108. getCurrentPosition• 3rd parameter to getCurrentPosition callpositionopts = {enableHighAccuracy: true} ;…navigator.geolocation.getCurrentPosition(handler, problemhandler, positionopts);• Add form coutput for = mylat; document.coutput.lon.value = mylong; document.coutput.acc.value = position.coords.accuracy; document.coutput.alt.value = position.coords.altitude; document.coutput.altacc.value = position.coords.altitudeAccuracy; document.coutput.heading.value = position.coords.heading; document.coutput.speed.value = position.coords.speed;
  109. 109. Next application: persistent storage• Normal situation: no changes to client computer beyond downloaded files.• cookies invented (with a pleasing name) to be files associated with each browser to be used only by same server site. – convenience: IDs and passwords, preferences, etc. – behavioral marketing!• Early HTML supported cookies. localStorage is a new variation.• CAUTION: Firefox requires the program to run on a server! Chrome allows running locally.• workshop/geolocationdistance4.html
  110. 110. Opening(after permission)
  111. 111. New base
  112. 112. Objective: add to maps app• 3 buttons: store base, retrieve base stored, change base to last marker• localStorage used name-value pairs.• Do error checking! – check for ability to do localStorage – check if there is a stored time.
  113. 113. Strategy• Three buttons, invoking store(), retrieve(), and changebasetomarker()• Use try { } catch(e) { } . The code in try will NOT trigger an error, but if there is one, will go to catch.• Also use typeof(localStorage) to test if this is defined.
  114. 114. <button onClick="javascript:store();">Store base. </button><button onClick="javascript:retrieve();">Restore last base. </button><button onClick="javascript:changebasetomarker();" >Change base location to last marker. </button> <br/>
  115. 115. function store() { if (typeof(localStorage) == "undefined") { alert("Browser does not recognize HTML local storage."); }else { try { localStorage.setItem("baselat", t()); localStorage.setItem("baselng",blatlng.lng ()); localStorage.setItem("basename",basename); } catch(e) { alert("Error with use of local storage: "+e);}}return false; }
  116. 116. function retrieve() { if (typeof(localStorage) == "undefined") {alert("Browser does not recognize HTML local storage.");}else { try { oldlat= localStorage.getItem("baselat"); oldlng = localStorage.getItem("baselng"); oldname = localStorage.getItem("basename"); if (oldlat==null) { alert("No base stored");} else {makemap(Number(oldlat),Number(oldlng)); basename = oldname; document.getElementById("header").innerHTML = "Base location is "+basename; } } catch(e) { alert("Error with use of local storage: "+e);} }return false; }
  117. 117. changes base to markerfunction changebasetomarker() { if (lastmarker!="undefined") { makemap(,lastma rker.lng()); basename = "marker"; }}
  118. 118. Comments• Error checking good!• Many GIS programs with common/similar features• Need to determine where information goes – my locations array kept information in my JavaScript
  119. 119. Plug for Book• introduce application, mainly familiar games.• critical requirements• HTML5 (CSS, JavaScript) features• complete code: comments• Many chapters involve sets of applications• Introduction to programming• NOTE: not encyclopedic on features isbn=9781430233831
  120. 120. Applications (HTML5 features)• Favorite sites• Dice game: drawing arcs & rectangles• Bouncing ball: drawing, including gradient, form validation, timed events• Cannonball & Slingshot: drawing lines & images, mouse events, rotation & translation, programmer-defined objects• Memory polygons & pictures: drawing, mouse events (clicking on card), timing
  121. 121. Applications (HTML5 features)• Quiz: dynamically created HTML markup, mouse events on elements, video• Mazes: mouse events, drawing, localStorage, radio buttons• Rock, Paper, Scissors: drawing, audio• Hangman: drawing lines and arcs (ovals), dynamic HTML markup• Blackjack: key events, drawing images, footer
  122. 122. Conclusion• Please email with comments on this tutorial and HTML5 for – professional use – educational use• Thank you•