Android lets you change the button’s image at runtime depending on it’s states like s focused or pressed.
This is achieved using selectors .The selector xml is created in drawable folder ,which is a sub folder of res folder. In this example when the button is pressed the background image changes.
The selector.xml is given bellow
<?xml version=”1.0″ encoding=”utf-8″?>
<selector xmlns:android=”http://schemas.android.com/apk/res/android” >
<item android:drawable=”@drawable/ok_pressed”
android:state_pressed=”true” />
<item android:drawable=”@drawable/ok” />
</selector>
Code in layout file :
Here, we set selector as the background of the button
<Button
android:id=“@+id/b1”
android:layout_width=“wrap_content”
android:layout_height=“wrap_content”
android:background=“@drawable/selector”
android:text=“1”
/>
Also, we can dynamically replace selector images in the following manner.
StateListDrawable -Lets you assign a number of graphic images to a single Drawable and swap out the visible item by a string ID value.
Button button=(button) findViewById(R.id.button_id);
StateListDrawable state = new StateListDrawable();
state = new StateListDrawable();
//add new image resource for a specific state
state.addState(new int[] {android.R.attr.state_pressed},
getResources().getDrawable(R.drawable.btn_up_cyan));
state.addState(new int[] {android.R.attr.state_focused},
getResources().getDrawable(R.drawable.btn_up_cyan));
button.setBackgroundDrawable(state);//set the background of button according to ‘state’
Hope this post is helpful . 🙂
