storing value of child item in expandable listview so that it doesn't disappear when another group is clicked

I have implemented expandable listview, in that for each group I have one child. when we click on child two toggle button drops down.One button is to increase the value while another is to decrease the value (increment and decrement counter) , the value gets stored in edittext. The problem I am getting is that when I move to another group, the value that I stored in edittext of previous group gets disappeared i.e. it changes to null.