java - Why do you have to declare "Integer int1" before I can use it in an onCreate and in a onClick method? -

there answer related this, didn't understand it.. i'm new related coding, go easy on me please. have:

package com.example.robert.rekenmachine;  import android.support.v7.app.actionbaractivity; import android.os.bundle; import android.view.menu; import android.view.menuitem; import android.widget.edittext; import android.view.view; import android.widget.textview;      public class mainactivity extends actionbaractivity {      edittext num1text, num2text;     textview ans;         @override     public void oncreate(bundle savedinstancestate) {         super.oncreate(savedinstancestate);         setcontentview(r.layout.activity_main);          num1text = (edittext)findviewbyid(r.id.num1text);         num2text = (edittext)findviewbyid(r.id.num2text);         ans = (textview)findviewbyid(r.id.ans);         integer int1 = integer.parseint(num1text.gettext().tostring()), int2 = integer.parseint(num2text.gettext().tostring());         float ft1 = float.parsefloat(num1text.gettext().tostring()), ft2 = float.parsefloat(num2text.gettext().tostring());       }      public void add(view v){         float ansft = ft1          ans.settext(integer.tostring(1));       }     @override     public boolean oncreateoptionsmenu(menu menu) {         // inflate menu; adds items action bar if present.         getmenuinflater().inflate(r.menu.menu_main, menu);         return true;     }      @override     public boolean onoptionsitemselected(menuitem item) {         // handle action bar item clicks here. action bar         // automatically handle clicks on home/up button, long         // specify parent activity in androidmanifest.xml.         int id = item.getitemid();          //noinspection simplifiableifstatement         if (id == r.id.action_settings) {             return true;         }          return super.onoptionsitemselected(item);     } } 

so @ float ansft = ft1, says can't resolve symbol. wondering, why? tried same things did num1text, num2text , ans, typed: float ft1;. resolve symbol. wondering if explain it, since think great deal in future if understand logic behind all.

ans declared in scope { ... } of class, , accessible methods field of object.

int1 local variable in 1 method. method's scope restricted braces { ... } , variable live during call method. not accessible outside.

now 1 make int1 field. want fetch recent value of text field num1text.

private int getint1() {     int int1 = integer.parseint(num1text.gettext().tostring());     return int1; } 

or simply:

private int getint1() {     return integer.parseint(num1text.gettext().tostring()); } 

and do

public void add(view v) {     int int1 = getint1(); // take latest value.     ans.settext(integer.tostring(int1)); 

or shorter

    ans.settext(integer.tostring(getint1())); }