What is wrong with my android simple calculator app?

I'm new to android and this is my first application, it seems fine to me but ev开发者_如何学编程ery time I pressed the calculate button it seems to stop unexpectedly and force close.

package com.test.simplecalc;

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

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

    final Button myButton = (Button) findViewById(R.id.myButton);
    final EditText firstNum = (EditText)findViewById(R.id.firstNum);
    final EditText secondNum = (EditText)findViewById(R.id.secondNum);
    final EditText finalNum = (EditText)findViewById(R.id.finalNum);

    myButton.setOnClickListener(new OnClickListener() {
        public void onClick(View v) {
            int num1 = 0;

            try {
                num1 = Integer.parseInt(firstNum.getText().toString());
            } catch(NumberFormatException nfe) {
               Toast.makeText(MainActivity.this, "Could not parse" + nfe, Toast.LENGTH_SHORT).show();
            }

            int num2 = 0;

            try {
                num2 = Integer.parseInt(secondNum.getText().toString());
            } catch(NumberFormatException nfe) {
               Toast.makeText(MainActivity.this, "Could not parse" + nfe, Toast.LENGTH_SHORT).show();
            }
            int num3 = num1 + num2;
            finalNum.setText(num3);
        }
    });
}

}

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It's likely that one of the two blocks is throwing something other than NumberFormatException. (My guess would be a NullPointerException in the call to toString().)

Try changing the caught exception in each case to Exception and see if this reveals the problem.

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just try

num3.toString() 

while printing the answer, and better to use textview for showing answer