Question

I am new to android programming but there is something small that i can’t seem to find online.
My problem is i want to use a variable from the onCreate method in another method.
Im sure this is online somewhere but whatever i have searched i couldnt find a soultion. Maybe i am phrasing this all wrong….
I want to re-use the doubles in the onCreate to perform an IF statement to see if the answer is correct. App crashes at the moment..

Here is my code:

 public class Addition extends Activity implements OnClickListener{

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_addition);

    View results = findViewById(R.id.check_button1);


//set event listener
    results.setOnClickListener(this);


        double myRanNumber1; {

        // variable we will use to store a random number
        myRanNumber1 = Math.random(); 
        //myRanNumber generated between 0.000000... & 9.9999...
        myRanNumber1 = myRanNumber1 *10; 
        // myRanNumber between 0.00.. and 9.999..
        myRanNumber1 = (int) myRanNumber1;// myRanNumber between 0 and 9 (fraction chopped off)
        double myRanNumber=(myRanNumber1);
        DecimalFormat df = new DecimalFormat("####");
        String number = df.format(myRanNumber);
        String printnumber = number;
        TextView random = (TextView) findViewById(R.id.TextViewRand);
        random.setText(printnumber); 
        }

         double myRanNumber2; 
         {
        // variable we will use to store a random number
        myRanNumber2 = Math.random(); 
        //myRanNumber generated between 0.000000... & 9.9999...
        myRanNumber2 = myRanNumber2 *10; 
        // myRanNumber between 0.00.. and 9.999..
        myRanNumber2 = (int) myRanNumber2;// myRanNumber between 0 and 9 (fraction chopped off)
        double myRanNumber=(myRanNumber2);
        DecimalFormat df = new DecimalFormat("####");
        String number = df.format(myRanNumber);
        String printnumber = number;
        TextView random = (TextView) findViewById(R.id.TextViewRand1);
        random.setText(printnumber); 
        }

         double additionRes1 = addition1(myRanNumber1, myRanNumber2);
         Intent theIntent = new Intent(this, Results.class);


         Bundle b = new Bundle();
         b.putDouble("key", additionRes1);
         theIntent.putExtras(b);
         startActivity(theIntent);

}

private double addition1 (double myRanNumber1, double myRanNumber2)

{

    return (double) (myRanNumber1 + myRanNumber2);
}

any help be very much appriciated 🙂

Answer 1

Basic scoping of variables requires that you declare them as classwide variables if you want to manipulate them from different functions.

public class MainActivity extends Activity {

    //Declare a class variable to use in this class
    public Double myNumber1;
    public Double myNumber2;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            myNumber1 = 250;
            myNumber2 = 10;

            //mySum is only available for use within this method
            Double mySum = addition1 (myNumber1, myNumber2);

    }
    private double addition1 (double myRanNumber1, double myRanNumber2) {
       return myRanNumber1 + myRanNumber2;
    }
}