Layouts and widgets are created using the default UI theme of our project. We can change the appearance of the elements of the UI by creating styles. Styles can be grouped to create a theme, and a theme can be applied to an activity or to the whole application. Some themes are provided by default, such as the Holo style. Styles and themes are created as resources under the /src/res/values folder.
To continue our example, follow these steps:
Open the main layout using the graphical editor. The selected theme for our layout is indicated as AppTheme in the toolbar. This theme was created for our project and can be found in the
stylesfile at/src/res/values/styles.xml.Open the
stylesfile. You will notice that this theme is an extension of another theme,Theme.AppCompat.Light.DarkActionBar.To customize the theme, edit the
stylesfile. Add the highlighted line in the AppTheme definition to change the window background color:<style name="AppTheme" parent="android:Theme...