Slide 10.2: Android user interface (UI) (Cont.)

Android User Interface (UI) (Cont.)

The name of an XML element for a view is respective to the Android class it represents. So a TextView element creates a TextView widget in your UI, and a LinearLayout element creates a LinearLayout view group. For example, a simple vertical layout with a text view and a button looks like this:

01<?xml version="1.0" encoding="utf-8"?>
02<LinearLayout
03  xmlns:android           = "http://schemas.android.com/apk/res/android"
04  android:layout_width    = "fill_parent"
05  android:layout_height   = "fill_parent"
06  android:orientation     = "vertical" >
07  <TextView
08    android:id            = "@+id/text"
09    android:layout_width  = "wrap_content"
10    android:layout_height = "wrap_content"
11    android:text          = "I am a TextView" />
12  <Button
13    android:id            = "@+id/button"
14    android:layout_width  = "wrap_content"
15    android:layout_height = "wrap_content"
16    android:text          = "I am a Button" />
17</LinearLayout>

When you load a layout resource in your app, Android initializes each node of the layout into a runtime object you can use to define additional behaviors, query the object state, or modify the layout. For a complete guide to creating a UI layout, see XML Layouts.

User Interface Components
You don’t have to build all of your UI using View and ViewGroup objects. Android provides several app components that offer a standard UI layout for which you simply need to define the content. These UI components each have a unique set of APIs that are described in their respective documents, such as Adding the App Bar, Dialogs, and Status Notifications.