Book Image

Mastering OpenLayers 3

By : Gábor Farkas
Book Image

Mastering OpenLayers 3

By: Gábor Farkas

Overview of this book

OpenLayers 3 allows you to create stunning web mapping and WebGIS applications. It uses modern, cutting edge browser technologies. It is written with Closure Library, enabling you to build browser-independent applications without painful debugging ceremonies, which even have some limited fallback options for older browsers. With this guide, you will be introduced to the world of advanced web mapping and WebGIS. First, you will be introduced to the advanced features and functionalities available in OpenLayers 3. Next, you will be taken through the key points of creating custom applications with OpenLayers 3. You will then learn how to create the web mapping application of yours (or your company's) dream with this open source, expense-free, yet very powerful library. We’ll also show you how to make amazing looking thematic maps and create great effects with canvas manipulation. By the end of this book, you will have a strong command of web mapping and will be well on your way to creating amazing applications using OpenLayers 3.
Table of Contents (17 chapters)
Mastering OpenLayers 3
Credits
About the Author
About the Reviewer
www.PacktPub.com
Preface
Index

Building a measuring control


We have come to our last example in this chapter. In this example, called ch05_measure, we will harness the full power of interactions and build a completely custom one in which we manually handle every event type. This example has three parts, so stay sharp. Firstly, as usual, we create a CSS rule for our new control button:

.toolbar .ol-measure button {
    background-image: url(../../res/button_measure.png);
}

One button is enough for this control, as we will implement two functionalities (length and area measurement) into a single interaction.

Creating the interaction

In the interaction's constructor, we accept two properties in an object literal: a reference to our map object and an optional style object or style function. As interactions do not have the exposed setMap and getMap methods, we need a reference to our map; thus, if it is not there, we return an error. If the style is not defined, we simply assign a default style, which is a simplified version of...