How can I use findviewbyid in static class?

I have a static class:

public static void culculateFprice(){
    TextView FinalBuy = (TextView) findViewById(R.id.buyText);
    int Pprice = MainActivity.pepperoni.getFinalPrice();
    int Cprice = MainActivity.calzone.getFinalPrice();
    int QCprice = MainActivity.quattrostagioni.getFinalPrice();
    int QFprice = MainActivity.quattroformaggi.getFinalPrice();
    int Mprice = MainActivity.mexican.getFinalPrice();
    int FinalPrice = Pprice + Cprice + QCprice + QFprice + Mprice;
    FinalBuy.setText("Стоимось вашего заказа: " + FinalPrice + " руб.");
}

How can I use find findViewById in this class?
I call this method from this method

public static void onPlus(int i){
        ArrayList<String> list = listok();
        switch (list.get(i)){
            ...
        }
        adapteR.refreshData(listokadd());
        culculateFprice();
    }

And have problem "Non-static method "findViewById(int)" cannot be referenced from a static context"

I assume this function exists in your Activity class and you would like to process some information based on the View. There are two ways you can solve this:

1. Remove the static modifier and let the instance take care of this.
2. Create a field that holds a View reference that gets created as soon as your layout is set.

So your Activity will hold the field:

class MyActivity extends Activity {
    static View FinalBuy; // needs to be static, otherwise would give same error
}

@Override
void onCreate(Bundle savedInstance) {
    // after setLayout
    FinalBuy = (TextView) findViewById(R.id.buyText);
}

But to save your code from a potential runtime error, use an if...else block in your static method:

public static void culculateFprice(){
    if(FinalBuy != null) {
        // your code here.
    }
}

This problem is basic Java and not Android. That is how Java language is designed to provide instance vs. static methods for the programs.

This static View declaration leads to a potential design flaw because this View will outlive the Activity. Instead of this, you should consider using the approach I suggested in the list as option 1 and see why you are unable to use an instance method in your program. You should read more on this thread.

This will likely need you to change your other fields of MainActivity to be declared as non-static as well!