### opdracht 4 ###

### activity_main.xml ###

<androidx.constraintlayout.widget...>

	...

    <Button
        android:id="@+id/button4"
        android:layout_width="180dp"
        android:layout_height="50dp"
        android:layout_marginStart="52dp"
        android:onClick="startBellen"
        android:text="bel 123"
        app:layout_constraintStart_toEndOf="@+id/button1"
        tools:layout_editor_absoluteY="0dp" />

    ...

</androidx.constraintlayout.widget.ConstraintLayout>

### MainActivity.java ###

public class MainActivity extends AppCompatActivity {

	...

    public void startBellen (View view){

        Intent intent = new Intent("android.intent.action.DIAL",
        Uri.fromParts("tel", "123", null));
        startActivity(intent);

    }

    ...

}