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App Dev Worksheet: Events

App development lesson 17: Events: on tap, do this · Set 1 · 40 questions
TalentJR

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.

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

Answer key

  1. 13
  2. 3
  3. ON
  4. Hi, Arjun!
  5. ON
  6. 2
  7. OFF
  8. 30
  9. 2
  10. 4
  11. Well done, Riya!
  12. a tap event
  13. Hello, Arjun!
  14. a timer event
  15. 4
  16. a timer event
  17. a tap event
  18. True
  19. Well done, Aman!
  20. 2
  21. something that happens
  22. Welcome, Arjun!
  23. 1
  24. 12
  25. 14
  26. False
  27. handler
  28. ON
  29. Well done, Kabir!
  30. the user taps a button
  31. a load event
  32. True
  33. 14
  34. OFF
  35. Welcome, Riya!
  36. False
  37. Hi, Zoya!
  38. 14
  39. Hello, Zoya!
  40. an action

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