### oefening 2 ###

public class MainActivity extends AppCompatActivity {

    EditText firstNumber;
    EditText secondNumber;
    TextView addResult;
    Button btnAdd;
    double num1, num2, sum;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        firstNumber = (EditText)findViewById(R.id.txtNumber1);
        secondNumber = (EditText)findViewById(R.id.txtNumber2);
        addResult = (TextView)findViewById(R.id.txtResult1);
        btnAdd = (Button)findViewById(R.id.btnAdd);

        btnAdd.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                try {

                    num1 = Double.parseDouble(firstNumber.getText().toString());
                    num2 = Double.parseDouble(secondNumber.getText().toString());
                    sum = num1 + num2;

                    addResult.setText(Double.toString(sum));

                    } catch (Exception e) {

                        addResult.setText(e.getMessage());

                    }
            }
        });
    }

}