NullPointerException while setting LayoutParams [duplicate]

Answer 1

Since you are creating a Button programmatically b will not have any layout params set. So you'll need to set them manually like this:

ViewGroup.LayoutParams params = new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT);
b.setLayoutParams(params);

Or at least check if params are not null before changing them

    ViewGroup.LayoutParams params = b.getLayoutParams();
    if (params != null) {
        params.width= ViewGroup.LayoutParams.MATCH_PARENT;
        params.height = ViewGroup.LayoutParams.WRAP_CONTENT;
    } else
        params = new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT);