java - Android: Passing TextView as parameter to external function returns nullpointerexception -

i'm trying pass textview parameter external class perform functionality i'm hitting nullpointerexception each time.

activity.java

tv = (textview) findviewbyid(r.id.tv); log.v("", "contents: " + tv.gettext().tostring()); // works fine externalclass.addviewtolist(tv); externalclass.printviewcontents(tv.gettext().tostring()); 

external class

public list<view> _views;  // doesn't work public void addviewtolist(view v) {     try {         this._views.add(v);         log.v("", "added " + v.getid() + " list");     }     catch(nullpointerexception ex) {         log.e("", "nullpointerexception when adding view list");     } }  // works fine public void printviewcontents(string contents) {     log.v("",contents); } 

so know view has been found in layout.xml , has been initialized, question how pass view activity external class.

thanks

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edit

forgot lists need initalised arraylist

cheers!

your _views list isnt initialized i.e youre trying write data null. solve need write:

public list<view> _views = new list<>(); 

instead of just:

public list<view> _views; 

for less headache recommend work array list instead:

public arraylist<view> list = new arraylist<>(); 

now work :)