Why is app shutting down and catch-clause doesn´t catch error?
<p>I have two fields that i want to calculate. The program works fine if i put in numbers in both fields, but if i have one empty and presses my "buttonSubtract" (calc-button) it just shuts down with "application closed...". Why doesn´t the catch-clause catch the exception?</p>

<pre><code>protected void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    buttonSubtract = (Button) findViewById(R.id.buttonsubtract);
    editTextNumber1 = (EditText) findViewById(R.id.textnumber1);
    editTextNumber2 = (EditText) findViewById(R.id.textnumber2);
    textSum = (TextView) findViewById(R.id.textViewSum);

    try
    buttonSubtract.setOnClickListener(new OnClickListener()
        {
            @Override
            public void onClick(View v)
            {
                if (editTextNumber1.getText().toString() == ""
                        || editTextNumber2.getText().toString() == "")
                {
                    textSum.setText("Put numbers in both fields");

                } else
                {
                    int sum = Integer.parseInt(editTextNumber1.getText()
                            .toString())
                            - Integer.parseInt(editTextNumber2.getText()
                                    .toString());
                    textSum.setText("sum: " + sum);
                }
            }
        });
    } catch (NumberFormatException e)
    {
        textSum.setText("Put numbers in both fields");
    }
</code></pre>
