set Selector for Button Programmatically issues

I have a row of buttons and i am setting their selectors for background and text programatically.

background_selector.xml

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://ift.tt/nIICcg">

    <item android:drawable="@android:color/white" android:state_pressed="true"/>
    <item android:drawable="@color/black_500"/>

</selector>

color_selector.xml

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://ift.tt/nIICcg">

    <item android:state_pressed="true" android:color="@color/black_500"/>
    <item android:color="@android:color/white"/>

</selector>

and i am setting these selector for button as follows:

private void setButtonBackgrounds(Drawable buttonDrawable) {
int sdk = android.os.Build.VERSION.SDK_INT;

        if (sdk < android.os.Build.VERSION_CODES.JELLY_BEAN) {
            btnT.setBackgroundDrawable(buttonDrawable);
        } else {
            btnT.setBackground(buttonDrawable);
        }
}

button's xml:

<Button
                android:id="@+id/btnT"
                android:layout_width="0dip"
                android:layout_height="match_parent"
                android:layout_weight="0.20"
                android:background="?android:attr/selectableItemBackground"
                android:text="@string/button_t"
                android:textSize="22sp" />

This is the same for all the buttons in the row. The problem is When i click on "T" button, the adjacent button is also changing its state. Please look at the image below.

Why is this happening? I am not sure why this is happening. Can someone help me with this.