App Dev Worksheet: Events

App development lesson 17: Events: on tap, do this · Set 42 · 40 questions

Developer's tip (When this, do that): Event → handler → action: “on tap, do this”. The handler runs once for every tap. Counter: start + taps × step. A limit stops it growing; on = !on flips ON / OFF.

1. 1.👆 The user taps the button 7 times. What number does the label show now?
   let likes = 0;
   button.onTap = function () {
     if (likes < 2) {
       likes = likes + 1;
     }
     label.text = likes;
   };
2. 2.👆 The user taps the button 5 times. What number does the label show now?
   let points = 3;
   button.onTap = function () {
     points = points + 5;
     label.text = points;
   };
3. 3.👆 The user types Riya in nameBox and taps the button 1 time. What does the label show?
   button.onTap = function () {
     label.text = "Welcome, " + nameBox.text + "!";
   }; (a) Welcome, nameBox.text! (b) Riya (c) Welcome! (d) Welcome, Riya!
4. 4.👆 Which of these is an event? (a) the icon colour (b) a list of names (c) the user taps a button (d) the font size
5. 5.👆 The user taps the button 6 times. What number does the label show now?
   let points = 4;
   button.onTap = function () {
     points = points + 1;
     label.text = points;
   };
6. 6.👆 The user taps the button 5 times. What number does the label show now?
   let points = 0;
   button.onTap = function () {
     points = points + 1;
     label.text = points;
   };
7. 7.👆 The user types Meera in nameBox and taps the button 1 time. What does the label show?
   button.onTap = function () {
     label.text = "Hello, " + nameBox.text + "!";
   }; (a) Hello! (b) Meera (c) Hello, nameBox.text! (d) Hello, Meera!
8. 8.👆 The user types Arjun in nameBox and taps the button 1 time. What does the label show?
   button.onTap = function () {
     label.text = "Welcome, " + nameBox.text + "!";
   }; (a) Welcome, Arjun! (b) Welcome! (c) Welcome, nameBox.text! (d) Arjun
9. 9.👆 The user taps the button 7 times. What number does the label show now?
   let likes = 0;
   button.onTap = function () {
     if (likes < 5) {
       likes = likes + 1;
     }
     label.text = likes;
   };
10. 10.👆 The user taps the button 3 times. What number does the label show now?
    let stars = 6;
    button.onTap = function () {
      stars = stars + 1;
      label.text = stars;
    };
11. 11.👆 The user types Kabir in nameBox and taps the button 1 time. What does the label show?
    button.onTap = function () {
      label.text = "Welcome, " + nameBox.text + "!";
    }; (a) Kabir (b) Welcome! (c) Welcome, nameBox.text! (d) Welcome, Kabir!
12. 12.👆 Code that runs when an event happens is called a ___. (a) header (b) handler (c) hashtag (d) headline
13. 13.👆 The user taps the button 2 times. What does the label show now?
    let on = false;
    button.onTap = function () {
      on = !on;
      if (on) {
        label.text = "ON";
      } else {
        label.text = "OFF";
      }
    }; (a) OFF (b) ON
14. 14.👆 The user taps the button 8 times. What number does the label show now?
    let likes = 0;
    button.onTap = function () {
      if (likes < 2) {
        likes = likes + 1;
      }
      label.text = likes;
    };
15. 15.👆 The user taps the button 6 times. What number does the label show now?
    let score = 1;
    button.onTap = function () {
      score = score + 1;
      label.text = score;
    };
16. 16.True or false: a finger hits Like is a tap event. (a) True (b) False
17. 17.👆 The user taps the button 6 times. What number does the label show now?
    let likes = 0;
    button.onTap = function () {
      if (likes < 4) {
        likes = likes + 1;
      }
      label.text = likes;
    };
18. 18.👆 The user types Zoya in nameBox and taps the button 1 time. What does the label show?
    button.onTap = function () {
      label.text = "Well done, " + nameBox.text + "!";
    }; (a) Zoya (b) Well done, Zoya! (c) Well done! (d) Well done, nameBox.text!
19. 19.👆 The user taps the button 3 times. What number does the label show now?
    let likes = 0;
    button.onTap = function () {
      if (likes < 3) {
        likes = likes + 1;
      }
      label.text = likes;
    };
20. 20.👆 The user taps the button 1 times. What does the label show now?
    let on = false;
    button.onTap = function () {
      on = !on;
      if (on) {
        label.text = "ON";
      } else {
        label.text = "OFF";
      }
    }; (a) ON (b) OFF
21. 21.👆 What kind of event is this: the user taps Play? (a) a tap event (b) a text event (c) a load event (d) a timer event
22. 22.👆 What kind of event is this: the user presses Save? (a) a load event (b) a timer event (c) a tap event (d) a text event
23. 23.👆 What kind of event is this: a countdown hits zero? (a) a timer event (b) a text event (c) a tap event (d) a load event
24. 24.True or false: the app starts up is a load event. (a) False (b) True
25. 25.👆 The user taps the button 3 times. What number does the label show now?
    let likes = 0;
    button.onTap = function () {
      if (likes < 2) {
        likes = likes + 1;
      }
      label.text = likes;
    };
26. 26.True or false: the user presses Save is a tap event. (a) False (b) True
27. 27.👆 The user types Arjun in nameBox and taps the button 1 time. What does the label show?
    button.onTap = function () {
      label.text = "Hi, " + nameBox.text + "!";
    }; (a) Arjun (b) Hi, Arjun! (c) Hi, nameBox.text! (d) Hi!
28. 28.👆 The user types Kabir in nameBox and taps the button 1 time. What does the label show?
    button.onTap = function () {
      label.text = "Hi, " + nameBox.text + "!";
    }; (a) Hi, nameBox.text! (b) Kabir (c) Hi! (d) Hi, Kabir!
29. 29.👆 The user taps the button 4 times. What number does the label show now?
    let coins = 10;
    button.onTap = function () {
      coins = coins + 2;
      label.text = coins;
    };
30. 30.👆 An event in an app is ___. (a) something that happens (b) a kind of list (c) a colour theme (d) an app store
31. 31.👆 The user taps the button 3 times. What number does the label show now?
    let points = 7;
    button.onTap = function () {
      points = points + 5;
      label.text = points;
    };
32. 32.👆 The user taps the button 3 times. What number does the label show now?
    let score = 9;
    button.onTap = function () {
      score = score + 1;
      label.text = score;
    };
33. 33.👆 The user taps the button 4 times. What number does the label show now?
    let points = 10;
    button.onTap = function () {
      points = points + 5;
      label.text = points;
    };
34. 34.👆 The user taps the button 7 times. What does the label show now?
    let on = false;
    button.onTap = function () {
      on = !on;
      if (on) {
        label.text = "ON";
      } else {
        label.text = "OFF";
      }
    }; (a) ON (b) OFF
35. 35.👆 What kind of event is this: a finger hits Like? (a) a text event (b) a load event (c) a timer event (d) a tap event
36. 36.👆 The user types Aman in nameBox and taps the button 1 time. What does the label show?
    button.onTap = function () {
      label.text = "Welcome, " + nameBox.text + "!";
    }; (a) Welcome, Aman! (b) Welcome, nameBox.text! (c) Welcome! (d) Aman
37. 37.👆 The user types Riya in nameBox and taps the button 1 time. What does the label show?
    button.onTap = function () {
      label.text = "Hello, " + nameBox.text + "!";
    }; (a) Hello, nameBox.text! (b) Riya (c) Hello, Riya! (d) Hello!
38. 38.👆 A tap handler runs how many times if the user taps 4 times? (a) 1 (b) 4 (c) 8 (d) 0
39. 39.👆 “On tap → do this” links an event to ___. (a) a web address (b) a font (c) a charger (d) an action
40. 40.True or false: the screen first opens is a tap event. (a) False (b) True

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