android - Unable to change TextView size on button click, why? -

hello guys right i'm working on app in there many quotes, in textview , want change size of textview on button click, if small button clicked textview should become small, if large clicked should large, etc. each time press button app force closes! what's problem? here's onclicklistener button:

small = (button) findviewbyid(r.id.small);  small.setonclicklistener(new view.onclicklistener() {             public void onclick(view v) {                 textview tv = (textview)findviewbyid(r.id.quotes);                 tv.settextsize(20);             }         }); 

p.s: textview , button in different activities.

there no way change textview size button 1 activity in other activity. nullpointerexception because findviewbyid method not find view , return null. should use sharedpreferences. should save text size value when click button , read in second activity.

in setting activity:

   small.setonclicklistener(new view.onclicklistener() {         public void onclick(view v) {             sharedpreferences sharedpreferences = preferencemanager.getdefaultsharedpreferences(youractivity.this.getbasecontext());             sharedpreferences.edit()             .putfloat("font_size", 22)             .apply();         }     }); 

in activity have textview

     textview tv = (textview)findviewbyid(r.id.quotes);      sharedpreferences sharedpreferences = preferencemanager.getdefaultsharedpreferences(youractivity.this.getbasecontext());      tv.settextsize(sharedpreferences.getfloat("font_size", 13/*default value*/));