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

Time for action – using DOM manipulation with OpenStreetMap map images

Reusing knowledge about OpenLayers renderers from Chapter 3, Charting the Map Class and OpenStreetMap from Chapter 4, Interacting with Raster Data Source, let's review how to manipulate the DOM and changing OpenStreetMap tiles sources on the fly.

So, let's start with the official OpenLayers example from http://openlayers.org/en/v3.0.0/examples/simple.html using Page inspector.

Open the file and at the end of the URL you get from your browser add ?renderer=dom

  1. Click on the Page Inspector icon (or right-click on image and click Inspect in the menu) and hover over the images. .
  2. Then, on one of the img tags, right-click on Edit attributes, as illustrated in the following screenshot:
    Time for action – using DOM manipulation with OpenStreetMap map images
  3. Next, you will see that you can change the value in our example, http://b.tile.openstreetmap.org/2/2/1.png, of the src attribute. So, replace its value with http://tile.stamen.com/toner/2/2/1.png and see the result. In the Elements panel, the img (for the image tag) src attribute contains http://b.tile.openstreetmap.org/2/2/1.png. If you remember, URL can be separated in two parts. The first part, http://b.tile.openstreetmap.org/, (called base URL), will change when the second part, 2/2/1.png, will change according to images you hover on. Here, we only change the first part.
  4. Repeat the process by changing the image you hover on and the base URL you use. The value you can use for base URL can be http://d.tile.stamen.com/watercolor/, http://b.tile.opencyclemap.org/cycle/, and http://otile2.mqcdn.com/tiles/1.0.0/osm/.
  5. The result obtained will look like the screenshot that follows:
    Time for action – using DOM manipulation with OpenStreetMap map images

What just happened?

We saw how to modify attributes of HTML elements using the Page Inspector on images. You also saw the correspondence between highlight on the web page and code content in the Elements panel when hovering over. You also rediscovered some different OpenStreetMap backgrounds.

The Network panel

Chrome DevTools's Network panel is a tool we often use throughout this book. It basically provides a way for us to monitor a network activity by viewing all the requests and responses the web page is making. In addition to the initial page load network activity, we are also able to monitor all of the asynchronous JavaScript requests that are made by the web page. Without AJAX, we will have to refresh our entire page any time we want to do anything with our OpenLayers map. So, for example, every time you zoom in, OpenLayers makes a series of requests to the map server to get new map images, and the map server's response is a new map image that OpenLayers then displays. This request/response method is handled via AJAX; without it, we would have to refresh the entire page after every request.

Note

See Appendix B, More details on Closure Tools and Code Optimization Techniques, where a small web history and a diagram covers AJAX.

The Network panel allows us to see the URL that is being requested, the GET or POST parameters, the server's status response, the type of resource requested, the size of the response, and the time it took to complete the request. Let's take a look at what the Network panel looks like for the example from the previous official example used when reviewing Elements panel:

The Network panel

Before we talk about the requests being made, take a look at the buttons above the lists of requests—the first one is dedicated to Record Network Log and the second Clear helps you remove the list of network calls. Then, you can activate Filter, which displays a submenu to filter by resources types for example, Documents, Stylesheets, Images, but also by the type of requests such as XHR or WebSockets. The Filter icon also activates a full text search box. The fourth icon is Use small resource rows. The two checkboxes are available, Preserve Log will cause the list of requests to persist, or not get deleted, on page reloads, while Disable cache will not allow you to use cache. For better performances, some assets such as scripts or images can be kept in your browser memory to speed your browsing experience when you visit the same website again. The drawback is when you debug, you can use an outdated file.

Now, let's break down the actual request list.

The request list

The request list shows us all the requests the page makes. Each URL in the previous screenshot is a URL that OpenLayers is making a request to. By clicking on each request, we can see more information about the request, including the full request URL and the response. When we are in the Headers sub-tab, we get a Request URL, Request Method, and Status Code, and after we get all details of Request Headers and Response Headers. The Request URL tab gives all the parameters. The Response tab provides us with the server's response to our request:

The request list

Parameters

Take a look again at the list—when we look at the first image in the screenshot, the row has the name 1.png. The method, GET in this case, specifies that the request type is GET, which basically means we are embedding variables inside the URL itself, with optional key=value pairs, separated by an & sign.

When we mouse over a URL, we can see more of it; we see the full URL, which may contain a bunch of variables in the key=value&key=value&.... format. In our case, we only have a full URL like http://c.tile.openstreetmap.org/2/1/1.png when hovering.

As we saw in all OpenStreetMap examples through the book, we didn't need parameters. If you remember in Chapter 1, Getting Started with OpenLayers, we told you that OpenLayers consumes cartographic data; some can come from dynamic web mapping server, others from pregenerated data. Our example relies on pregenerated data so that there are no parameters added contrary, for instance, to a WMS data source.

The Sources panel

The Sources panel is very powerful. It enables you to view and edit JavaScript and CSS files loaded from the web page. You are not restricted to only view all the JavaScript code associated with the page in this panel; you can use it to do real-time code debugging. You can set watch expressions, view the stack, set breakpoints, and so on. If these terms are foreign, don't worry, we will review some of them.

For example, we want to quickly talk about enabling Pause on exceptions. With this option enabled, Chrome DevTools will stop the web page whenever a JavaScript error is encountered. This makes it very easy to quickly pinpoint where your page is blowing up at. To enable it, simply click on the Pause on exceptions button icon (be careful, it's not the same as an Pause Script Execution icon).

Keep note of this when you enable it. We've been frustrated more than once when developing because we forgot that it had been enabled. When it is enabled, the button isn't gray, as demonstrated with the icon:

The Sources panel

Another tip in this panel, is the ability to unminify JavaScript. It's really useful to track errors. You can open a web page with a compressed JavaScript file. If you click on the icon with open/close brackets called Pretty Print, you will see the difference.

You are maybe wondering why we spoke so much about this panel. When you start to make complex web mapping applications, this panel is the best way to analyze how an application works. When you're developing or reusing an already existing code, you can already guess the behavior of the code, but you can't confirm it. The key feature of the debugger is to make this confirmation. Let's see an example of how you can use it.