Book Image

Android Application Development Cookbook - Second Edition

By : Kyle Mew
Book Image

Android Application Development Cookbook - Second Edition

By: Kyle Mew

Overview of this book

The Android OS has the largest installation base of any operating system in the world; there has never been a better time to learn Android development to write your own applications, or to make your own contributions to the open source community! This “cookbook” will make it easy for you to jump to a topic of interest and get what you need to implement the feature in your own application. If you are new to Android and learn best by “doing,” then this book will provide many topics of interest. Starting with the basics of Android development, we move on to more advanced concepts, and we’ll guide you through common tasks developers struggle to solve. The first few chapters cover the basics including Activities, Layouts, Widgets, and the Menu. From there, we cover fragments and data storage (including SQLite), device sensors, the camera, and GPS. Then we move on more advanced topics such as graphics and animation (including OpenGL), multi-threading with AsyncTask, and Internet functionality with Volley. We’ll also demonstrate Google Maps and Google Cloud Messaging (also known as Push Notifications) using the Google API Library. Finally, we’ll take a look at several online services designed especially for Android development. Take your application big-time with full Internet web services without having to become a server admin by leveraging the power of Backend as a Service (BaaS) providers.
Table of Contents (23 chapters)
Android Application Development Cookbook Second Edition
Credits
Disclaimer
About the Authors
About the Reviewer
www.PacktPub.com
Preface
Index

Changing layout properties during runtime


In Android development, it's generally the preferred practice to define the UI with XML and the application code in Java, keeping the User Interface code separate from the application code. There are times where it is much easier or more efficient, to alter (or even build) the UI from the Java code. Fortunately, this is easily supported in Android.

We saw a small example of modifying the layout from code in the previous recipe, where we set the number of GridView column to display in the code. In this recipe, we will obtain a reference to the LayoutParams object to change the margin during runtime.

Getting ready

Here we will set up a simple layout with XML and use a LinearLayout.LayoutParams object to change the margins of a View during runtime.

How to do it....

  1. Open the activity_main.xml file and change the layout from RelativeLayout to LinearLayout. It will look as follows:

    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    ...