Android Java.langnullpointerexception Null Object Reference

I am trying to initialize all the navigation bar buttons and assign Black background color, when user clicks on one of the button, that one should change color and all other should

Solution 1:

I think this is the problem:

LinearLayoutlinearLayout= (LinearLayout) v.findViewById(R.id.bottom_nav_bar);

You are assuming the LinearLayout is inside the view which is clicked - my best guess is this is not true (you probably want to get the clicked view's parent, not child). You have 2 options:

1. Start iterating the view hierarchy to the top (i.e. call v.getParent()) until you reach the LinearLayout.
2. Call findViewById on the containing activity (or fragment's root view) instead of the v object.