Android Application Development For Dummies, 2nd Edition

Adding a Toggle Button View

Android devices come fully equipped with various views that include buttons, check boxes, and text-entry fields so that you can quickly build your user interface. Some views are more complex, such as a date picker, a clock, and zoom controls.

Views also provide user interface events that inform you when a user has interacted with the particular view, such as tapping a button.

You need to add a button view to your application so that you can toggle silent mode on the phone.

To add a button to your layout, type the following code after ImageView:

<Button

android:id=”@+id/toggleButton”

android:layout_width=”wrap_content”

android:layout_height=”wrap_content”

android:layout_gravity=”center_horizontal”

android:text=”Toggle Silent Mode”

/>

You have now added a button to your view with an ID resource of toggle Button. That’s how you reference the button in the Java code. (Chapter 5 tackles coding.)

The height and width are set to wrap_content, which informs the Android layout system to place the view onscreen and occupy only as much usable space as it needs. The layout_gravity property is the same as the ImageView above it, centered horizontally.

The final property that has been introduced in this view is the text property of the button, which sets the button’s text to Toggle Silent Mode.

Your full code base should now look like this:

<?xml version=”1.0” encoding=”utf-8”?>

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

android:orientation=”vertical” ...