android setText

Question

我想計算圓的周長並將結果放入TextView中。

public void hesapla1(View v){ 

     double pi = 3.14; 
     double yari = R.id.e1; 

     double alan = pi * Math.pow(yari,2); 

     sonuc1.setText((int) alan); 

    } 

Answer 1

只能在TextView設置String值：

sonuc1.setText(String.valueOf(alan));