Android App crashes at line 54(Integer.parseInt) and not entirely sure why

I've been debugging my app with my phone and all the logcat errors I get refer to line 54 in my activity where I parse a String into an Int. The basic idea of the app is a penny converter in which the user enters the number of pennies they wants to convert and is divided from quarters down to the remainder pennies. At this point I'm not sure if I'm properly catching the event and have gone back and forth on using an anonymous inner class and just implementing in the class.

Here's the code for the java app:

public class PennyConverterActivity extends Activity

{



    EditText et;

    TextView tv;



    int cents;

    int remaining;

    int quarters;

    int dimes;

    int nickels;

    int pennies;

    String result;



    @Override



    public void onCreate(Bundle b)

    {

        super.onCreate(b);

        setContentView(R.layout.main);



        et = (EditText) findViewById(R.id.penny);



        et.setText(result);



        et.setOnKeyListener(new View.OnKeyListener() 

        {



            @Override

            public boolean onKey(View v, int keyCode, KeyEvent event) 

            {

                if((event.getAction() == KeyEvent.ACTION_DOWN) && (keyCode == KeyEvent.KEYCODE_ENTER))

                {

                    result = et.getText().toString();

                    return (true);

                }



                return (true);

            }

        }); 





        cents = Integer.parseInt(result); //LogCat error refers to this line



        tv = (TextView) findViewById(R.id.quarters);



        quarters = cents / 25;

        tv.setText(R.string.quarters);

        remaining = cents % 25;



        tv = (TextView) findViewById(R.id.dimes);



        dimes = remaining / 10;

        tv.setText(R.string.dimes);

        remaining = remaining % 10;



        tv = (TextView) findViewById(R.id.nickels);



        nickels = remaining / 5;

        tv.setText(R.string.nickles);



        tv = (TextView) findViewById(R.id.pennies);



        pennies = remaining % 5;

        tv.setText(R.string.pennies);



    }



}

and my Logcat errors

02-26 15:26:30.602: E/AndroidRuntime(25020): FATAL EXCEPTION: main

02-26 15:26:30.602: E/AndroidRuntime(25020): java.lang.RuntimeException: Unable to start activity ComponentInfo{CS211D.HW03.PennyConverter/CS211D.HW03.PennyConverter.PennyConverterActivity}: java.lang.NumberFormatException: unable to parse 'null' as integer

02-26 15:26:30.602: E/AndroidRuntime(25020):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647)

02-26 15:26:30.602: E/AndroidRuntime(25020):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)

02-26 15:26:30.602: E/AndroidRuntime(25020):    at android.app.ActivityThread.access$1500(ActivityThread.java:117)

02-26 15:26:30.602: E/AndroidRuntime(25020):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)

02-26 15:26:30.602: E/AndroidRuntime(25020):    at android.os.Handler.dispatchMessage(Handler.java:99)

02-26 15:26:30.602: E/AndroidRuntime(25020):    at android.os.Looper.loop(Looper.java:130)

02-26 15:26:30.602: E/AndroidRuntime(25020):    at android.app.ActivityThread.main(ActivityThread.java:3683)

02-26 15:26:30.602: E/AndroidRuntime(25020):    at java.lang.reflect.Method.invokeNative(Native Method)

02-26 15:26:30.602: E/AndroidRuntime(25020):    at java.lang.reflect.Method.invoke(Method.java:507)

02-26 15:26:30.602: E/AndroidRuntime(25020):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)

02-26 15:26:30.602: E/AndroidRuntime(25020):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)

02-26 15:26:30.602: E/AndroidRuntime(25020):    at dalvik.system.NativeStart.main(Native Method)

02-26 15:26:30.602: E/AndroidRuntime(25020): Caused by: java.lang.NumberFormatException: unable to parse 'null' as integer

02-26 15:26:30.602: E/AndroidRuntime(25020):    at java.lang.Integer.parseInt(Integer.java:356)

02-26 15:26:30.602: E/AndroidRuntime(25020):    at java.lang.Integer.parseInt(Integer.java:332)

02-26 15:26:30.602: E/AndroidRuntime(25020):    at CS211D.HW03.PennyConverter.PennyConverterActivity.onCreate(PennyConverterActivity.java:52)

02-26 15:26:30.602: E/AndroidRuntime(25020):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)

02-26 15:26:30.602: E/AndroidRuntime(25020):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)

02-26 15:26:30.602: E/AndroidRuntime(25020):    ... 11 more