Question

I’m trying to write my first Android app. It will take a number input by a user in an EditText field, convert it to an integer, then find the factors. I want to port this from a Java program that I wrote before. I have stubs working to the point that I have a UI, but I haven’t yet ported the code that will find the factors. I’m stuck trying to convert the EditText to an integer. If I insert either of the following lines, the program crashes in the emulator. Log.Cat says, “Caused by NumberFormatExcepion: Unable to parse ” as an integer.”

Any suggestions are appreciated.

userNumber is the name of the value taken from the EditText field, and the EditText field is also named userNumber. I don’t know if that’s bad form or not. I want to assign the value of userNumber to the integer value userInt. userInt will then be factored.

Either of these approaces will cause the problem:

userNumber = (EditText) findViewById(R.id.userNumber);
userInt = Integer.parseInt(userNumber.getText().toString());


Integer userInt = new Integer(userNumber.getText().toString());

The EditText block of XML looks like this:

<EditText
    android:id="@+id/userNumber"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:ems="10"
    android:inputType="number" >

    <requestFocus />
</EditText>

Here is the relevant code from the class:

public class AndroidFactoringActivity extends Activity {

// Instance Variables
EditText userNumber;
Button factorButton;
TextView resultsField;
int factorResults = 1;
int userInt = 0;  // This comes out if using Integer userInt

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    resultsField = (TextView) findViewById(R.id.resultsField);
    factorButton = (Button) findViewById(R.id.factorButton);
    userNumber = (EditText) findViewById(R.id.userNumber); 
                // userNumber is also the name of the EditText field.

    // userInt = Integer.parseInt(userNumber.getText().toString());

    // Integer userInt = new Integer(userNumber.getText().toString());

    resultsField.append("\n" + String.valueOf(userInt)); 
               //Later, this will be factorResults, not userInt.
               // Right now, I just want it to put something on the screen.      

}   
} 

Answer 1

You’re trying to parse the int in your onCreate method, which occurs before the user has a chance to enter anything into the EditText. Hence the exception from trying to parse an empty string.

You’ll have to either make a button to press, which will then parse the int out of the EditText, or attach a listener to the EditText that will parse it when something is typed into it.