It is long back since I did the last post. Let’s start the actual thing now. With all your development environment setup, it is time for some real android programming. User Interface (UI) is one of the most important aspects of the Android programming. It can give you’re the important edge that will attract users to your app and is taken to be seriously off. One of the reasons for popularity of Android platform is its simple-to-understand and highly interactive UI.
So how do you make UIs in Android?
This is such a huge topic that it will be taken in various parts.
The View and ViewGroup class
View and ViewGroup Class are the basic building blocks of Android UI elements. ViewGroup Class takes care of grouping of various elements known as (YES!!! you guessed it) Views. Views are also known as widgets e.g. TextView, Button ListView etc. Each of the widget is a class in itself and has a set of properties and values that can be manipulated for defining its behaviour. ViewGroup also known as layouts contain these widgets within them and decide the positioning of these widgets within them and provide the final look and feel of the application.
That is about some basic background. Now let’s get down to some business. In Android programming, UI can be made using both Java i.e. programmatically and statically using XML (Extended Markup Language). The XML approach provides for clear separation of UI code so that Java can be used for the core code of your application.
A Basic XML Layout
We will edit the main.xml in our Hello World Application. All the layouts are placed in the res/layout/ folder in your project.(The code is in red color)
<?xml version="1.0" encoding="utf-8"?>
android:text= "How's The View"
You can view the code on github as well.
The XML code consists of tags (here LinearLayout , TextView, Button)
and attributes( layout_width, layout_height,textSize etc.android is a namespace).
Most of the attributes are self-explanatory.The output of the above code is :
The most important and highly used attributes are layout_width and layout_height which take values wrap_content and fill_parent .As the name suggests they make the size of the widgets wrap their content or fill their parent(i.e. their container) completely.Here LinearLayout is a ViewGroup which places the contents in a linear fashion.Here the orientation is vertical therefore the TextView and the Button are placed in the order they appear in the xml file in one below the other.
To set the layout to an Activity following function is used
Next Part will talk about different layouts and referencing widgets in Java code.Till then
Happy Droiding :-)