Android Change textView text from another method/class -

after click on button1, layout , class gets called. want change text of textview out of class 2 results in app crash java.lang.nullpointerexception

important parts of class 1

public static textview a; protected void oncreate(bundle savedinstancestate) {         super.oncreate(savedinstancestate);         setcontentview(r.layout.activity_main); 

[button stuff in class 1]

 setcontentview(r.layout.raten);                       final    textview = (textview) findviewbyid(r.id.a); //the textview wanna chage                  max = 10;                       easy easy = new easy(); // other class                       easy.e(); 

[now method in class 1 should change text]

    public static void tx(int i)     {  a.settext("adsfasdf");     } 

[important parts of class 2 ("easy")]

public void e(){         system.out.println("called class easy");      int max = mainactivity.max;     system.out.println(max);     (int i= 0; i<max; i++){         system.out.println("runde"+i);  mainactivity.tx(i);      } 

i know, people asked such questions didn't find working solution. understood, can't access ui things outside ui thread , nullpointerexception appears, because uses "empty" public static textview a; , not final textview = (textview) findviewbyid(r.id.a).

but how can make visible other methods?

sorry if post looks messed didn't konw how explain situation in better way

rather defining new local variable a, assign static.

change

final    textview = (textview) findviewbyid(r.id.a); //the textview wanna chage 

to

a = (textview) findviewbyid(r.id.a); //the textview wanna chage