Black color comes instead a transparent background for textview in android

You have specified only the stroke of the Shape, but it needs background. It seems that black is default.

Change your button_style.xml shape by adding the solid transparent background:

<shape>
    <stroke
        android:width="2dp"
        android:color="#88C425" />
    <corners android:radius="20dp" />
    <solid android:color="@android:color/transparent" />
</shape>

For a simple TextView you could do this

(TextView) txtListChild.setBackgroundColor(Color.TRANSPARENT);

But if you're using a ListView, you'd need to find the itemView layout being used for each item and set it there... Something like this

if (convertView == null) {
    LayoutInflater infalInflater = (LayoutInflater) this._context
                    .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    convertView = infalInflater.inflate(R.layout.list_item, null);
    convertView.setBackgroundColor(Color.TRANSPARENT);
}