Circle.java

package com.android;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;
import android.widget.Button;
import android.widget.Toast;


public class Circle extends Activity {
    /** Called when the activity is first created. */
    EditText radius;
    EditText editarea;
    EditText circumference;

    Button Calculate;

    MyCircle handler;

    @Override
    public void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        radius = (EditText)findViewById(R.id.editRad);
        editarea = (EditText)findViewById(R.id.editarea);
        circumference = (EditText)findViewById(R.id.editcirc);
        Calculate   = (Button)findViewById(R.id.button1);

        handler = new MyCircle();

        Calculate.setOnClickListener(new View.OnClickListener()
        {

            public void onClick(View v)
            {
                double n = Double.parseDouble(radius.getText().toString());
                handler.setRadius(n);
                double area = handler.SolveArea();
                double circ = handler.SolveCirc();

                circumference.setText(String.valueOf(area));
                editarea.setText(String.valueOf(circ));

                Toast toast = Toast.makeText(getApplicationContext(), "Area and Circumference Calculated", Toast.LENGTH_SHORT);
				toast.show();
            }
        });
    }
}


MyCircle.java
package com.android;

public class MyCircle
{
    private double n = 0.0;

    public MyCircle(){}

    public MyCircle(Double radius)
    {
        this.n = radius;
    }
    public double getRadius()
    {
        return n;
    }
    public void setRadius(double radius)
    {
        this.n = radius;
    }
    public double SolveArea()
    {
        double area = Math.PI*Math.pow(getRadius(), 2);
        return area;
    }
    public double SolveCirc()
    {
        double circ = Math.PI*getRadius()*2;
        return circ;
    }
}