Question

I’m really not sure why I get this error. It’s probably something simple but I’m new to this.

final Button calculate = (Button) findViewById(R.id.calculate);
calculate.setOnClickListener(new View.OnClickListener() {
        // Implement the OnClickListener callback       
        private void onClick(Button calculate) {
                double perimeter = 2 * (Math.PI * entry); //error on this line
                System.out.print(perimeter);

                }

        public void onClick(View v) {
        // TODO Auto-generated method stub
            }
        }

    );

Answer 1

It would appear that entry is an EditText object … you can’t multiply that.

I’m going to make an educated guess that you want to multiply what’s in that EditText. Looking at the javadocs, You need to get the text with entry.getText().toString(), and convert it to a numeric type (provided the text represents a numeric type).

double myInputDouble = Double.parseDouble(entry.getText().toString());

(or Integer.parseInt() if that’s what you’re expecting)

http://developer.android.com/reference/android/widget/EditText.html
http://docs.oracle.com/javase/6/docs/api/java/lang/Double.html
http://docs.oracle.com/javase/6/docs/api/java/lang/Integer.html