Table of Contents for
OpenLayers 3 : Beginner's Guide

Version ebook / Retour

Cover image for bash Cookbook, 2nd Edition OpenLayers 3 : Beginner's Guide by Erik Hazzard Published by Packt Publishing, 2015
  1. Cover
  2. Table of Contents
  3. OpenLayers 3 Beginner's Guide
  4. OpenLayers 3 Beginner's Guide
  5. Credits
  6. About the Authors
  7. About the Reviewers
  8. www.PacktPub.com
  9. Preface
  10. What you need for this book
  11. Who this book is for
  12. Sections
  13. Time for action – heading
  14. Conventions
  15. Reader feedback
  16. Customer support
  17. 1. Getting Started with OpenLayers
  18. Advantages of using OpenLayers
  19. What, technically, is OpenLayers?
  20. Anatomy of a web mapping application
  21. Connecting to Google, Bing Maps, and other mapping APIs
  22. Time for action – downloading OpenLayers
  23. Time for action – creating your first map
  24. Where to go for help
  25. OpenLayers issues
  26. OpenLayers source code repository
  27. Getting live news from RSS and social networks
  28. Summary
  29. 2. Key Concepts in OpenLayers
  30. Time for action – creating a map
  31. Time for action – using the JavaScript console
  32. Time for action – overlaying information
  33. OpenLayers' super classes
  34. Key-Value Observing with the Object class
  35. Time for action – using bindTo
  36. Working with collections
  37. Summary
  38. 3. Charting the Map Class
  39. Time for action – creating a map
  40. Map renderers
  41. Time for action – rendering a masterpiece
  42. Map properties
  43. Time for action – target practice
  44. Map methods
  45. Time for action – creating animated maps
  46. Events
  47. Views
  48. Time for action – linking two views
  49. Summary
  50. 4. Interacting with Raster Data Source
  51. Layers in OpenLayers 3
  52. Common operations on layers
  53. Time for action – changing layer properties
  54. Tiled versus untiled layers
  55. Types of raster sources
  56. Tiled images' layers and their sources
  57. Time for action – creating a Stamen layer
  58. Time for action – creating a Bing Maps layer
  59. Time for action – creating tiles and adding Zoomify layer
  60. Image layers and their sources
  61. Using Spherical Mercator raster data with other layers
  62. Time For action – playing with various sources and layers together
  63. Time For action – applying Zoomify sample knowledge to a single raw image
  64. Summary
  65. 5. Using Vector Layers
  66. Time for action – creating a vector layer
  67. How the vector layer works
  68. The vector layer class
  69. Vector sources
  70. Time for action – using the cluster source
  71. Time for action – creating a loader function
  72. Time for action – working with the TileVector source
  73. Time for action – a drag and drop viewer for vector files
  74. Features and geometries
  75. Time for action – geometries in action
  76. Time for action – interacting with features
  77. Summary
  78. 6. Styling Vector Layers
  79. Time for action – basic styling
  80. The style class
  81. Time for action – using the icon style
  82. Have a go hero – using the circle style
  83. Multiple styles
  84. Time for action – using multiple styles
  85. Style functions
  86. Time for action – using properties to style features
  87. Interactive styles
  88. Time for action – creating interactive styles
  89. Summary
  90. 7. Wrapping Our Heads Around Projections
  91. Time for action – using different projection codes
  92. Time for action – determining coordinates
  93. OpenLayers projection class
  94. Transforming coordinates
  95. Time for action – coordinate transforms
  96. Time for action – setting up Proj4js.org
  97. Time for action – reprojecting extent
  98. Time for action – using custom projection with WMS sources
  99. Time for action – reprojecting geometries in vector layers
  100. Summary
  101. 8. Interacting with Your Map
  102. Time for action – converting your local or national authorities data into web mapping formats
  103. Time for action – testing the use cases for ol.interaction.Select
  104. Time for action – more options with ol.interaction.Select
  105. Introducing methods to get information from your map
  106. Time for action – understanding the forEachFeatureAtPixel method
  107. Time for action – understanding the getGetFeatureInfoUrl method
  108. Adding a pop-up on your map
  109. Time for action – introducing ol.Overlay with a static example
  110. Time for action – using ol.Overlay dynamically with layers information
  111. Time for action – using ol.interaction.Draw to share new information on the Web
  112. Time for action – using ol.interaction.Modify to update drawing
  113. Understanding interactions and their architecture
  114. Time for action – configuring default interactions
  115. Discovering the other interactions
  116. Time for action – using ol.interaction.DragRotateAndZoom
  117. Time for action – making rectangle export to GeoJSON with ol.interaction.DragBox
  118. Summary
  119. 9. Taking Control of Controls
  120. Adding controls to your map
  121. Time for action – starting with the default controls
  122. Controls overview
  123. Time for action – changing the default attribution styles
  124. Time for action – finding your mouse position
  125. Time for action – configuring ZoomToExtent and manipulate controls
  126. Creating a custom control
  127. Time for action – extending ol.control.Control to make your own control
  128. Summary
  129. 10. OpenLayers Goes Mobile
  130. Using a web server
  131. Time for action – go mobile!
  132. The Geolocation class
  133. Time for action – location, location, location
  134. The DeviceOrientation class
  135. Time for action – a sense of direction
  136. Debugging mobile web applications
  137. Debugging on iOS
  138. Debugging on Android
  139. Going offline
  140. Time for action – MANIFEST destiny
  141. Going native with web applications
  142. Time for action – track me
  143. Summary
  144. 11. Creating Web Map Apps
  145. Using geospatial data from Flickr
  146. Time for action – getting Flickr data
  147. A simple application
  148. Time for Action – adding data to your map
  149. Styling the features
  150. Time for action – creating a style function
  151. Creating a thumbnail style
  152. Time for action – switching to JSON data
  153. Time for action – creating a thumbnail style
  154. Turning our example into an application
  155. Time for action – adding the select interaction
  156. Time for action – handling selection events
  157. Time for action – displaying photo information
  158. Using real time data
  159. Time for action – getting dynamic data
  160. Wrapping up the application
  161. Time for action – adding dynamic tags to your map
  162. Deploying an application
  163. Creating custom builds
  164. Creating a combined build
  165. Time for action – creating a combined build
  166. Creating a separate build
  167. Time for action – creating a separate build
  168. Summary
  169. A. Object-oriented Programming – Introduction and Concepts
  170. Going further
  171. B. More details on Closure Tools and Code Optimization Techniques
  172. Introducing Closure Library, yet another JavaScript library
  173. Time for action – first steps with Closure Library
  174. Making custom build for optimizing performance
  175. Time for action – playing with Closure Compiler
  176. Applying your knowledge to the OpenLayers case
  177. Time for action - running official examples with the internal OpenLayers toolkit
  178. Time for action - building your custom OpenLayers library
  179. Syntax and styles
  180. Time for action – using Closure Linter to fix JavaScript
  181. Summary
  182. C. Squashing Bugs with Web Debuggers
  183. Time for action – opening Chrome Developer Tools
  184. Explaining Chrome Developer debugging controls
  185. Time for action – using DOM manipulation with OpenStreetMap map images
  186. Time for action – using breakpoints to explore your code
  187. Time for action – playing with zoom button and map copyrights
  188. Using the Console panel
  189. Time for action – executing code in the Console
  190. Time for action – creating object literals
  191. Time for action – interacting with a map
  192. Improving Chrome and Developer Tools with extensions
  193. Debugging in other browsers
  194. Summary
  195. D. Pop Quiz Answers
  196. Chapter 5, Using Vector Layers
  197. Chapter 7, Wrapping Our Heads Around Projections
  198. Chapter 8, Interacting with Your Map
  199. Chapter 9, Taking Control of Controls
  200. Chapter 10, OpenLayers Goes Mobile
  201. Appendix B, More details on Closure Tools and Code Optimization Techniques
  202. Appendix C, Squashing Bugs with Web Debuggers
  203. Index

Going offline

One of the great challenges in delivering content to the mobile web is that mobile devices can easily be disconnected from the Internet. As users move around, they go in and out of range of WIFI and cellular networks, and the state of their network connection can change frequently. Native applications on mobile devices solve this problem by being installed on the device. Many native applications also cache content for offline use and are designed to handle the transient nature of mobile network connections. Web browsers, including mobile web browsers, typically cache web page content to help pages load faster. While this can help mobile web applications quite a bit, the cache managed by the web browser is unreliable, can be cleared by user settings, and might not keep critical content for your application. The cache also doesn't provide a mechanism to store generated data and stores only assets required to load a web page.

In this section, we will introduce three technologies that can help you with taking a web application offline:

  • HTML5 ApplicationCache interface
  • HTML 5 Storage
  • Apache Cordova

The HTML 5 ApplicationCache interface

The HTML 5 ApplicationCache interface is designed to help address the unreliable nature of web browser caches by allowing a developer to control how content is cached for offline use. The ApplicationCache interface provides us with the following benefits:

  • Developers can specify exactly which resources to cache and ensure that users can navigate to all the content regardless of their network state
  • Developers can also specify which resources not to cache
  • Content in ApplicationCache is not displaced by new content in the normal browser cache, so it is much more reliable
  • Content is cached locally on the device, and so it will load much faster than across a network
  • Developers can update content and have only that content transferred, reducing load on web servers

If you are thinking Sounds great, lets get me some of that, read on!

Taking advantage of the ApplicationCache interface is actually very simple, and there are three steps we need to take:

  • Create a MANIFEST file
  • Reference the MANIFEST file in an HTML page
  • Serve the MANIFEST file from our web server correctly

Creating an ApplicationCache MANIFEST file

A MANIFEST file is a plain text file that you can create in any text editor. The easiest way to describe its content is by example, so let's take a look at a MANIFEST file and then describe it in detail:

CACHE MANIFEST
# version 2
CACHE:index.htmlscripts/app.jscss/styles.cssimages/logo.png
NETWORK:login.php
FALLBACK:images/large/ images/offline.jpg*.html /offline.html
SETTINGS:prefer-online

The first line is mandatory; it must contain the specific text CACHE MANIFEST.

The second line is a comment. Comments are any line starting with a # character. One important characteristic of ApplicationCache is that the browser will usually not replace cached content with an updated version from the server unless the MANIFEST file changes or the prefer-online setting is specified. It is a common convention to include a comment near the top of the MANIFEST file, indicating a date or version number. When content is updated, the date or version in the MANIFEST file can also be updated, which will trigger the browser to download changed content. The third line declares the CACHE section. The CACHE section explicitly declares URLs that will be stored in the ApplicationCache. This line can be optional. If it is omitted, any files after the first line will be considered part of the CACHE section up to the start of any other section. The following lines up to the NETWORK line define files, by URL, that are to be cached. Wildcards are not allowed in the CACHE section. Do not include the MANIFEST file in the list of files to be cached, or it will be very difficult for users to get updates. URLs can be relative or absolute and might point to resources on domains other than that of the page being loaded. Check the following line, for example:

CACHE:
http://another.server.com/logo.png

Next, comes the NETWORK section. This section contains a whitelist of resources that the browser will not cache (unless explicitly declared in the cache section), and which it is permitted to access when online. In this example, the browser can access login.php when online, and the results of loading that page will not be cached. This section is typically used to identify URLs that are part of a server API or content that cannot be used if it is out of date. URLs cannot contain wildcards, but a single wildcard character is allowed on a line by itself to indicate that any URL can be loaded. Check the following line for example:

NETWORK:
*

The FALLBACK section defines alternate resources to be used if a particular resource is not available. Wildcards and path matching are allowed in this section. The first line of the FALLBACK section shows how you would display the image from images/offline.jpg for any image in the images/large path that is unavailable. In the next line, we specify that any HTML page that cannot be accessed should use offline.html instead. URL prefixes are allowed (a path to a folder for instance), but the wildcard character * is not permitted. Also, only URLs in the same domain as the web page can be listed in this section. As of writing this book, only one value is permitted in the final SETTINGS section, the prefer-online setting. If this is present in the SETTINGS section, then the browser will attempt to access the server version of resources before using the cached version.

Note the following rules for a MANIFEST file:

  • The first line must contain the text CACHE MANIFEST.
  • A line starting with the # character is considered a comment.
  • Comments must be on their own line as the # character is a valid component of a URL.
  • Any non-comment lines after the first line are implicitly part of the CACHE section up to the start of one of the other sections. Thus the CACHE: line is not strictly needed.
  • Only spaces and tab characters are allowed for whitespace, and all other characters are considered part of a URL.
  • There are four distinct section types. The allowed section names are CACHE, NETWORK, FALLBACK, and SETTINGS. A section is started by putting the section name followed by the : character.
  • Sections can appear in any order and can be repeated.

Referencing a MANIFEST file in a web page

In order to trigger the use of an ApplicationCache MANIFEST file, you must include a reference to the MANIFEST file in your web page. This is done as an attribute of the <html> tag, as follows:

<html manifest="/myapp.appcache">

The value of the attribute is the URL to your MANIFEST file. Although the MANIFEST file can have any extension, it is standard practice to use .appcache as the file extension, and we recommend you follow this practice. The MANIFEST file must be delivered by a web server with mime-type of text/cache-manifest. The instructions for configuring a web server to serve particular files with a particular mime-type vary depending on the particular web server in use. Please consult the documentation for your web server to determine the best way to accomplish this.