Displays a button with an image (instead of text) that can be pressed
or clicked by the user. By default, an ImageButton looks like a regular
{@link android.widget.Button}, with the standard button background
that changes color during different button states. The image on the surface
of the button is defined either by the {@code android:src} attribute in the
{@code } XML element or by the
{@link #setImageResource(int)} method.
To remove the standard button background image, define your own
background image or set the background color to be transparent.
To indicate the different button states (focused, selected, etc.), you can
define a different image for each state. E.g., a blue image by default, an
orange one for when focused, and a yellow one for when pressed. An easy way to
do this is with an XML drawable "selector." For example:
<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
<item android:state_pressed="true"
android:drawable="@drawable/button_pressed" /> <!-- pressed -->
<item android:state_focused="true"
android:drawable="@drawable/button_focused" /> <!-- focused -->
<item android:drawable="@drawable/button_normal" /> <!-- default -->
</selector>
Save the XML file in your project {@code res/drawable/} folder and then
reference it as a drawable for the source of your ImageButton (in the
{@code android:src} attribute). Android will automatically change the image
based on the state of the button and the corresponding images
defined in the XML.
The order of the {@code - } elements is important because they are
evaluated in order. This is why the "normal" button image comes last, because
it will only be applied after {@code android:state_pressed} and {@code
android:state_focused} have both evaluated false.
See the Buttons
guide.
XML attributes
See {@link android.R.styleable#ImageView Button Attributes},
{@link android.R.styleable#View View Attributes}
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