How to set background of selected/unselected Button in the XML file

Question

I have custom buttons that are supposed to have different backgrounds depending if they are selected or not selected. I want to know if there is a way to state this in the XML file. I have a button for Celsius and a button for Fahrenheit. I want it to work where if one is selected, it stays "pressed" and unable to be clicked, while the other button can be pressed.

        <Button
            android:id="@+id/celsiusButton"
            android:text="C"
            android:background="@drawable/button_unpressed_shape"
            android:layout_weight="3"
            android:layout_height="match_parent"
            android:layout_width="0dip"
            android:gravity="center" />

        <Button
            android:id="@+id/fahrenheitButton"
            android:text="F"
            android:background="@drawable/button_unpressed_shape"
            android:layout_weight="3"
            android:layout_height="match_parent"
            android:layout_width="0dip"
            android:gravity="center" />

The Celsius button is defaulted to selected. I try working on it like this in my code, but it just seems to messy:

    tempText = (TextView) findViewById( R.id.temperatureId );
    celsiusButton = (Button) findViewById( R.id.celsiusButton );
    celsiusButton.setBackgroundDrawable( getResources().getDrawable( R.drawable.button_pressed_shape ) );
    celsiusButton.setClickable( false );

    celsiusButton.setOnClickListener( new OnClickListener() {
        public void onClick(View v) {
            if( hasRead ) {
                    celsiusButton.setBackgroundDrawable( getResources().getDrawable( R.drawable.button_pressed_shape ) );
                    celsiusButton.setClickable( false );
                    fahrenheitButton.setBackgroundDrawable( getResources().getDrawable( R.drawable.button_unpressed_shape ) );
                    fahrenheitButton.setClickable( true );
                    temperature = ( ( ( temperature - 32 ) * 5 ) / 9 );
                    tempText.setText( Double.toString( temperature ).substring( 0, ( Double.toString( temperature ).length() - 2 ) ) + " C" );
            }
        }       
    });

    fahrenheitButton = (Button) findViewById( R.id.fahrenheitButton );
    fahrenheitButton.setOnClickListener( new OnClickListener() {
        public void onClick( View v ) {
            if( hasRead ) {
                fahrenheitButton.setBackgroundDrawable( getResources().getDrawable( R.drawable.button_pressed_shape ) );
                celsiusButton.setBackgroundDrawable( getResources().getDrawable( R.drawable.button_unpressed_shape ) );
                celsiusButton.setClickable( true );
                fahrenheitButton.setClickable( false );
                temperature = ( ( temperature * 9 ) / 5 ) + 32;
                tempText.setText( Double.toString( temperature ).substring( 0, ( Double.toString( temperature ).length() - 2 ) ) + "° F" );
            }
        }
    });

Answer 1

To change background image:

public void onClick(View v) {
   if(v == ButtonName) {
     ButtonName.setImageResource(R.drawable.ImageName);
   }
}

Or, using an XML file:

<?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/login_selected" /> <!-- pressed -->
  <item android:state_focused="true"
   android:drawable="@drawable/login_mouse_over" /> <!-- focused -->
  <item android:drawable="@drawable/login" /> <!-- default -->
</selector>

In OnClick, just add this code:

ButtonName.setBackgroundDrawable(getResources().getDrawable(R.drawable.ImageName));