java - android : Is it possible to inherit from MainActivity class? -

i started learning java , android development week ago , have couple of basic things i'd want know.

the functioning of app has 10 buttons , each of them disabled after has been clicked once. if total of 5 buttons have been clicked, buttons must disabled. didn't use button array, want know why doesn't work. (all necessary imports have been made)

the mainactivity class goes this:

public class mainactivity extends appcompatactivity {  @override protected void oncreate(bundle savedinstancestate) {     super.oncreate(savedinstancestate);     setcontentview(r.layout.activity_main);     starttext(); }  class1 c1object = new class1();  textview textobj; button button1,button2,button3,button4 /* other 6 buttons*/ ;  public void starttext(){     textobj = (textview)findviewbyid(r.id.textview);     textobj.settext("no button has been clicked"); }  public void click1(view view) {     button1 = (button)findviewbyid(r.id.button1);     c1object.disablebutton(button1,textobj,1);  } public void click2(view view) {     button2 = (button)findviewbyid(r.id.button2);     c1object.disablebutton(button2,textobj,2); } public void click3(view view) {     button3 = (button)findviewbyid(r.id.button3);     c1object.disablebutton(button3,textobj,3); }  public void click4(view view) {     button4 = (button)findviewbyid(r.id.button4);     c1object.disablebutton(button4,textobj,4);  } // 6 more buttons  } 

class1 this:

public class class1 {  class2 c2object = new class2();  private int clickcount=0;  public void disablebutton(button b, textview t, int i) {     b.setenabled(false);     string str = integer.tostring(i);     t.settext("you clicked button: " + str);     clickcount++;     if(clickcount==5)         c2object.disableall(); } } 

and finally, class2 goes this:

public class class2 {  mainactivity mainobject = new mainactivity();  public void disableall(){      mainobject.button1.setenabled(false);     mainobject.button2.setenabled(false);     mainobject.button3.setenabled(false);     mainobject.button4.setenabled(false);     //similarly other 6 buttons  }  } 

if run app launches white screen shown , app closes.

after several tries, realized happens when created object of mainactivity class. tried inheriting mainactivity result same.

i tried changing class2 this:

public class class2 {  public void disableall(){      button b1 = (button)findviewbyid(r.id.button1);     b1.setenabled(false); //similarly other 9 buttons  }  } 

i noticed can't use findviewbyid here.

these things i'd know:

1. can inherit or create object of mainactivity?

2. why can't use findviewbyid class apart mainactivity?

3. what do disable buttons after clickcount==5?

4. you've seen way of coding. practices need follow? other suggestions make way of coding better?

thank in advance!

you cannot instantiate activity class via constructor. wont able write mainactivity mainobject = new mainactivity(). still wouldn't want if possible, creating new instance of mainactivity, whereas want conduct operations on buttons in existing mainactivity.

one way around supply mainactivity argument neither method or constructor. i.e.

class classtwo {      private mainactivity activity;      classtwo(mainactivity activity) {         this.activity = activity;     }      void disableall() {         activity.btn1.setenabled(false);         //etc...     }  } 

personally though think passing in activity here overkill, when want act on buttons. so, either pass buttons constructor argument instead of activity:

classtwo(button[] btns) {     this.btns = btns; } 

or, pass in interface. or consider supplying buttons argument in method, rather storing them in instance variable (i'd go this):

class classtwo {      classtwo(){} //default, empty constructor      void disableall(button[] btns) {         (button btn : btns) {             btn.setenabled(false);         }     }  }