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App Dev Worksheet: Events

App development lesson 17: Events: on tap, do this · Set 224 · 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 4 times. What number does the label show now?
    let score = 4;
    button.onTap = function () {
      score = score + 4;
      label.text = score;
    };
  2. 2.👆 The user taps the button 5 times. What number does the label show now?
    let stars = 4;
    button.onTap = function () {
      stars = stars + 1;
      label.text = stars;
    };
  3. 3.👆 The user taps the button 2 times. What number does the label show now?
    let score = 1;
    button.onTap = function () {
      score = score + 5;
      label.text = score;
    };
  4. 4.👆 What kind of event is this: the search box changes? (a) a tap event (b) a load event (c) a timer event (d) a text event
  5. 5.👆 The user taps the button 6 times. What number does the label show now?
    let coins = 2;
    button.onTap = function () {
      coins = coins + 1;
      label.text = coins;
    };
  6. 6.👆 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
  7. 7.True or false: the screen first opens is a timer event. (a) False (b) True
  8. 8.True or false: one second passes is a timer event. (a) True (b) False
  9. 9.👆 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
  10. 10.👆 The user taps the button 4 times. What number does the label show now?
    let lives = 8;
    button.onTap = function () {
      lives = lives + 2;
      label.text = lives;
    };
  11. 11.👆 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, nameBox.text! (b) Well done! (c) Well done, Aman! (d) Aman
  12. 12.👆 Which of these is an event? (a) a list of names (b) the font size (c) the user taps a button (d) the icon colour
  13. 13.👆 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
  14. 14.👆 A tap handler runs how many times if the user taps 4 times? (a) 8 (b) 4 (c) 0 (d) 1
  15. 15.True or false: a finger hits Like is a text event. (a) True (b) False
  16. 16.👆 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, Meera! (b) Welcome! (c) Meera (d) Welcome, nameBox.text!
  17. 17.👆 What kind of event is this: a countdown hits zero? (a) a timer event (b) a load event (c) a text event (d) a tap event
  18. 18.👆 The user taps the button 4 times. What number does the label show now?
    let score = 9;
    button.onTap = function () {
      score = score + 2;
      label.text = score;
    };
  19. 19.True or false: the user presses Save is a timer event. (a) True (b) False
  20. 20.True or false: a countdown hits zero is a text event. (a) False (b) True
  21. 21.👆 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
  22. 22.👆 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, Kabir! (b) Kabir (c) Hi, nameBox.text! (d) Hi!
  23. 23.👆 The user taps the button 4 times. What number does the label show now?
    let coins = 4;
    button.onTap = function () {
      coins = coins + 4;
      label.text = coins;
    };
  24. 24.👆 What kind of event is this: the user taps Play? (a) a tap event (b) a timer event (c) a text event (d) a load event
  25. 25.👆 The user taps the button 2 times. What number does the label show now?
    let coins = 10;
    button.onTap = function () {
      coins = coins + 1;
      label.text = coins;
    };
  26. 26.👆 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) Zoya (b) Hi, Zoya! (c) Hi! (d) Hi, nameBox.text!
  27. 27.True or false: the user presses Save is a load event. (a) True (b) False
  28. 28.👆 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
  29. 29.👆 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) Meera (b) Hi, nameBox.text! (c) Hi, Meera! (d) Hi!
  30. 30.👆 An event in an app is ___. (a) a colour theme (b) a kind of list (c) an app store (d) something that happens
  31. 31.👆 What kind of event is this: the user presses Save? (a) a load event (b) a timer event (c) a text event (d) a tap event
  32. 32.👆 “On tap → do this” links an event to ___. (a) an action (b) a web address (c) a font (d) a charger
  33. 33.👆 What kind of event is this: a finger hits Like? (a) a tap event (b) a load event (c) a text event (d) a timer event
  34. 34.👆 Code that runs when an event happens is called a ___. (a) header (b) headline (c) handler (d) hashtag
  35. 35.👆 What kind of event is this: a 5-minute alarm ends? (a) a timer event (b) a tap event (c) a load event (d) a text event
  36. 36.True or false: the search box changes is a text event. (a) True (b) False
  37. 37.👆 The user taps the button 4 times. What number does the label show now?
    let likes = 0;
    button.onTap = function () {
      if (likes < 3) {
        likes = likes + 1;
      }
      label.text = likes;
    };
  38. 38.👆 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) ON (b) OFF
  39. 39.True or false: the app starts up is a timer event. (a) False (b) True
  40. 40.👆 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, nameBox.text! (c) Well done! (d) Well done, Arjun!

Answer key

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

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