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App Dev Worksheet: Events

App development lesson 17: Events: on tap, do this · Set 269 · 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 2 times. What number does the label show now?
    let stars = 7;
    button.onTap = function () {
      stars = stars + 4;
      label.text = stars;
    };
  2. 2.👆 A tap handler runs how many times if the user taps 4 times? (a) 1 (b) 4 (c) 0 (d) 8
  3. 3.👆 The user taps the button 4 times. What number does the label show now?
    let points = 0;
    button.onTap = function () {
      points = points + 3;
      label.text = points;
    };
  4. 4.👆 The user taps the button 7 times. What number does the label show now?
    let likes = 0;
    button.onTap = function () {
      if (likes < 4) {
        likes = likes + 1;
      }
      label.text = likes;
    };
  5. 5.👆 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
  6. 6.👆 The user types Riya in nameBox and taps the button 1 time. What does the label show?
    button.onTap = function () {
      label.text = "Hi, " + nameBox.text + "!";
    };     (a) Hi, Riya! (b) Hi, nameBox.text! (c) Riya (d) Hi!
  7. 7.👆 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
  8. 8.👆 What kind of event is this: the app starts up? (a) a tap event (b) a load event (c) a timer event (d) a text event
  9. 9.👆 What kind of event is this: a finger hits Like? (a) a timer event (b) a text event (c) a tap event (d) a load event
  10. 10.👆 The user taps the button 5 times. What number does the label show now?
    let likes = 0;
    button.onTap = function () {
      if (likes < 3) {
        likes = likes + 1;
      }
      label.text = likes;
    };
  11. 11.👆 What kind of event is this: the user types a letter? (a) a load event (b) a tap event (c) a text event (d) a timer event
  12. 12.👆 The user taps the button 3 times. What number does the label show now?
    let score = 0;
    button.onTap = function () {
      score = score + 3;
      label.text = score;
    };
  13. 13.True or false: a countdown hits zero is a timer event. (a) True (b) False
  14. 14.👆 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, nameBox.text! (b) Hi, Arjun! (c) Arjun (d) Hi!
  15. 15.👆 What kind of event is this: one second passes? (a) a timer event (b) a load event (c) a text event (d) a tap event
  16. 16.👆 The user taps the button 6 times. What number does the label show now?
    let stars = 3;
    button.onTap = function () {
      stars = stars + 1;
      label.text = stars;
    };
  17. 17.👆 The user taps the button 1 times. What number does the label show now?
    let likes = 0;
    button.onTap = function () {
      if (likes < 2) {
        likes = likes + 1;
      }
      label.text = likes;
    };
  18. 18.👆 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
  19. 19.👆 The user taps the button 2 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.👆 What kind of event is this: the search box changes? (a) a load event (b) a timer event (c) a tap event (d) a text event
  21. 21.True or false: a 5-minute alarm ends is a timer event. (a) False (b) True
  22. 22.👆 The user taps the button 8 times. What number does the label show now?
    let likes = 0;
    button.onTap = function () {
      if (likes < 3) {
        likes = likes + 1;
      }
      label.text = likes;
    };
  23. 23.👆 An event in an app is ___. (a) a kind of list (b) something that happens (c) a colour theme (d) an app store
  24. 24.True or false: a countdown hits zero is a tap event. (a) True (b) False
  25. 25.👆 The user taps the button 6 times. What number does the label show now?
    let stars = 7;
    button.onTap = function () {
      stars = stars + 2;
      label.text = stars;
    };
  26. 26.👆 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
  27. 27.👆 Code that runs when an event happens is called a ___. (a) hashtag (b) headline (c) handler (d) header
  28. 28.👆 “On tap → do this” links an event to ___. (a) a charger (b) a web address (c) a font (d) an action
  29. 29.👆 What kind of event is this: the user taps Play? (a) a timer event (b) a load event (c) a tap event (d) a text event
  30. 30.👆 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;
    };
  31. 31.👆 The user taps the button 5 times. What number does the label show now?
    let score = 3;
    button.onTap = function () {
      score = score + 3;
      label.text = score;
    };
  32. 32.👆 The user taps the button 4 times. What number does the label show now?
    let score = 7;
    button.onTap = function () {
      score = score + 1;
      label.text = score;
    };
  33. 33.👆 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
  34. 34.True or false: the app starts up is a text event. (a) True (b) False
  35. 35.👆 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;
    };
  36. 36.True or false: the user types a letter is a text event. (a) True (b) False
  37. 37.👆 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) Kabir (b) Hi! (c) Hi, Kabir! (d) Hi, nameBox.text!
  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.👆 Which of these is an event? (a) a list of names (b) the user taps a button (c) the icon colour (d) the font size
  40. 40.👆 The user taps the button 5 times. What number does the label show now?
    let likes = 0;
    button.onTap = function () {
      if (likes < 5) {
        likes = likes + 1;
      }
      label.text = likes;
    };

Answer key

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

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