NullPointerException using SharedPreferences

I am having a problem with my code here. I am using SharedPreferences in my code, and I am getting a NullPointerException at one line in the code. Here's the full code:

    public class Exercise extends Activity {
String WEIGHT = "0";
String AGE = "0";
String FEET = "0";
String INCHES = "0";

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    setContentView(R.layout.exercise);

    SharedPreferences myPrefs = this.getSharedPreferences("myPrefs", MODE_WORLD_READABLE);
    SharedPreferences.Editor prefsEditor = myPrefs.edit();
    prefsEditor.putInt(WEIGHT, 0);
    prefsEditor.putInt(AGE, 0);
    prefsEditor.putInt(FEET,开发者_C百科 0);
    prefsEditor.putInt(INCHES, 0);
    prefsEditor.commit();


    final EditText weightField = (EditText) findViewById(R.id.EditTextWeight);
    try {
        prefsEditor.putInt(WEIGHT, Integer.parseInt(weightField.getText().toString()));
        prefsEditor.commit();
    } catch(NumberFormatException nfe) {
        System.out.println("Could not parse " + nfe);
    }   

The NullPointerException appears at this line:

prefsEditor.putInt(WEIGHT, Integer.parseInt(weightField.getText().toString()));

Thanks!

EDIT: Here's the activity that calls setContentView(R.layout.main):

public class CalorieIntakeCalculator extends Activity {
/** Called when the activity is first created. */


@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    setContentView(R.layout.main);

}

public void next(View view) {
    Intent intentExercise = new Intent(view.getContext(), Exercise.class);
    startActivityForResult(intentExercise, 0);
} 
}

When the "next" button is pushed in main.xml, it sends next which switches Activities from CalorieIntakeCalculator to Exercise.

---

Since you successfully used prefsEditor several times above that line, it seems like weightField must be null. Have you checked its value in the debugger?

EDIT: I also just noticed that you never assigned a value to WEIGHT, nor any of the other Strings for the SharedPreferences keys, so they are all null. You need to fix that.

String WEIGHT = "weight";
String AGE = "age";
String FEET = "feet";
String INCHES = "inches";

For the weight field, make sure there is an EditText in your exercise layout that has the id R.id.EditTextWeight