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App Dev Worksheet: Events

App development lesson 17: Events: on tap, do this · Set 118 · 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.True or false: a 5-minute alarm ends is a timer event. (a) False (b) True
  2. 2.👆 The user taps the button 3 times. What number does the label show now?
    let score = 10;
    button.onTap = function () {
      score = score + 4;
      label.text = score;
    };
  3. 3.👆 The user types Kabir in nameBox and taps the button 1 time. What does the label show?
    button.onTap = function () {
      label.text = "Hello, " + nameBox.text + "!";
    };     (a) Kabir (b) Hello! (c) Hello, Kabir! (d) Hello, nameBox.text!
  4. 4.👆 The user types Meera in nameBox and taps the button 1 time. What does the label show?
    button.onTap = function () {
      label.text = "Hi, " + nameBox.text + "!";
    };     (a) Hi, Meera! (b) Hi, nameBox.text! (c) Hi! (d) Meera
  5. 5.👆 “On tap → do this” links an event to ___. (a) a web address (b) an action (c) a charger (d) a font
  6. 6.👆 Code that runs when an event happens is called a ___. (a) header (b) handler (c) headline (d) hashtag
  7. 7.👆 What kind of event is this: a 5-minute alarm ends? (a) a load event (b) a tap event (c) a text event (d) a timer event
  8. 8.👆 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) OFF (b) ON
  9. 9.👆 The user taps the button 6 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
  10. 10.👆 What kind of event is this: the app starts up? (a) a timer event (b) a text event (c) a tap event (d) a load event
  11. 11.👆 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
  12. 12.True or false: the app starts up is a timer event. (a) True (b) False
  13. 13.👆 What kind of event is this: the search box changes? (a) a timer event (b) a load event (c) a text event (d) a tap event
  14. 14.👆 The user types Meera 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) Meera (c) Welcome, Meera! (d) Welcome!
  15. 15.👆 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! (b) Welcome, nameBox.text! (c) Welcome, Aman! (d) Aman
  16. 16.True or false: a 5-minute alarm ends is a text event. (a) False (b) True
  17. 17.👆 An event in an app is ___. (a) a kind of list (b) something that happens (c) an app store (d) a colour theme
  18. 18.👆 What kind of event is this: the user taps Play? (a) a text event (b) a timer event (c) a load event (d) a tap event
  19. 19.👆 The user taps the button 6 times. What number does the label show now?
    let likes = 0;
    button.onTap = function () {
      if (likes < 2) {
        likes = likes + 1;
      }
      label.text = likes;
    };
  20. 20.👆 A tap handler runs how many times if the user taps 4 times? (a) 8 (b) 1 (c) 4 (d) 0
  21. 21.True or false: the app starts up is a tap event. (a) False (b) True
  22. 22.👆 The user taps the button 6 times. What number does the label show now?
    let score = 3;
    button.onTap = function () {
      score = score + 1;
      label.text = score;
    };
  23. 23.👆 The user taps the button 3 times. What number does the label show now?
    let coins = 6;
    button.onTap = function () {
      coins = coins + 5;
      label.text = coins;
    };
  24. 24.True or false: a countdown hits zero is a timer event. (a) True (b) False
  25. 25.👆 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
  26. 26.👆 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) ON (b) OFF
  27. 27.👆 The user taps the button 2 times. What number does the label show now?
    let score = 2;
    button.onTap = function () {
      score = score + 2;
      label.text = score;
    };
  28. 28.True or false: the user taps Play is a timer event. (a) False (b) True
  29. 29.👆 The user taps the button 5 times. What number does the label show now?
    let score = 9;
    button.onTap = function () {
      score = score + 3;
      label.text = score;
    };
  30. 30.👆 The user taps the button 2 times. What number does the label show now?
    let score = 3;
    button.onTap = function () {
      score = score + 3;
      label.text = score;
    };
  31. 31.👆 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;
    };
  32. 32.👆 The user taps the button 6 times. What number does the label show now?
    let stars = 5;
    button.onTap = function () {
      stars = stars + 1;
      label.text = stars;
    };
  33. 33.👆 The user taps the button 3 times. What number does the label show now?
    let stars = 9;
    button.onTap = function () {
      stars = stars + 4;
      label.text = stars;
    };
  34. 34.True or false: one second passes is a load event. (a) True (b) False
  35. 35.👆 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) Arjun (b) Welcome, Arjun! (c) Welcome! (d) Welcome, nameBox.text!
  36. 36.👆 The user types Arjun in nameBox and taps the button 1 time. What does the label show?
    button.onTap = function () {
      label.text = "Well done, " + nameBox.text + "!";
    };     (a) Arjun (b) Well done, Arjun! (c) Well done! (d) Well done, nameBox.text!
  37. 37.👆 The user taps the button 2 times. What number does the label show now?
    let points = 7;
    button.onTap = function () {
      points = points + 1;
      label.text = points;
    };
  38. 38.👆 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
  39. 39.👆 What kind of event is this: a countdown hits zero? (a) a timer event (b) a tap event (c) a text event (d) a load event
  40. 40.👆 The user taps the button 3 times. What number does the label show now?
    let likes = 0;
    button.onTap = function () {
      if (likes < 4) {
        likes = likes + 1;
      }
      label.text = likes;
    };

Answer key

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

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