### opdracht 1 ###

public class MainActivity extends AppCompatActivity {

    ...
    double num1, num2, div;

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

        ...

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

                    ...

                    div = num1 / num2;

                    ...

                } catch (Exception e) {

                    ...

                }
            }
        });

    }
}