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App Dev Worksheet: Events

App development lesson 17: Events: on tap, do this · Set 293 · 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 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
  2. 2.👆 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;
    };
  3. 3.👆 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) Meera (d) Hi!
  4. 4.True or false: the user taps Play is a text event. (a) True (b) False
  5. 5.👆 What kind of event is this: the user presses Save? (a) a timer event (b) a load event (c) a text event (d) a tap event
  6. 6.True or false: the app starts up is a tap event. (a) True (b) False
  7. 7.👆 The user taps the button 6 times. What number does the label show now?
    let stars = 4;
    button.onTap = function () {
      stars = stars + 2;
      label.text = stars;
    };
  8. 8.👆 The user taps the button 3 times. What number does the label show now?
    let lives = 7;
    button.onTap = function () {
      lives = lives + 2;
      label.text = lives;
    };
  9. 9.True or false: the app starts up is a load event. (a) True (b) False
  10. 10.👆 Code that runs when an event happens is called a ___. (a) handler (b) headline (c) header (d) hashtag
  11. 11.True or false: one second passes is a timer event. (a) False (b) True
  12. 12.👆 The user taps the button 2 times. What number does the label show now?
    let likes = 0;
    button.onTap = function () {
      if (likes < 2) {
        likes = likes + 1;
      }
      label.text = likes;
    };
  13. 13.👆 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) Kabir (b) Well done, nameBox.text! (c) Well done! (d) Well done, Kabir!
  14. 14.👆 What kind of event is this: a finger hits Like? (a) a timer event (b) a load event (c) a tap event (d) a text event
  15. 15.👆 What kind of event is this: a countdown hits zero? (a) a load event (b) a text event (c) a timer event (d) a tap event
  16. 16.👆 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;
    };
  17. 17.👆 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
  18. 18.True or false: the user types a letter is a load event. (a) True (b) False
  19. 19.👆 The user taps the button 4 times. What number does the label show now?
    let stars = 8;
    button.onTap = function () {
      stars = stars + 3;
      label.text = stars;
    };
  20. 20.True or false: the search box changes is a timer event. (a) False (b) True
  21. 21.True or false: the user taps Play is a timer event. (a) False (b) True
  22. 22.👆 The user taps the button 4 times. What number does the label show now?
    let stars = 2;
    button.onTap = function () {
      stars = stars + 4;
      label.text = stars;
    };
  23. 23.👆 The user taps the button 2 times. What number does the label show now?
    let lives = 2;
    button.onTap = function () {
      lives = lives + 2;
      label.text = lives;
    };
  24. 24.True or false: the user taps Play is a tap event. (a) False (b) True
  25. 25.👆 The user taps the button 3 times. What number does the label show now?
    let points = 9;
    button.onTap = function () {
      points = points + 5;
      label.text = points;
    };
  26. 26.👆 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;
    };
  27. 27.👆 The user taps the button 7 times. What number does the label show now?
    let likes = 0;
    button.onTap = function () {
      if (likes < 3) {
        likes = likes + 1;
      }
      label.text = likes;
    };
  28. 28.👆 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
  29. 29.👆 The user types Meera 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, Meera! (d) Meera
  30. 30.👆 An event in an app is ___. (a) a colour theme (b) an app store (c) something that happens (d) a kind of list
  31. 31.👆 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! (c) Well done, Riya! (d) Well done, nameBox.text!
  32. 32.👆 What kind of event is this: the user types a letter? (a) a tap event (b) a timer event (c) a load event (d) a text event
  33. 33.👆 “On tap → do this” links an event to ___. (a) a web address (b) a charger (c) an action (d) a font
  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) OFF (b) ON
  35. 35.True or false: the screen first opens is a text event. (a) False (b) True
  36. 36.👆 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;
    };
  37. 37.True or false: a countdown hits zero is a text event. (a) False (b) True
  38. 38.👆 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
  39. 39.👆 The user taps the button 2 times. What number does the label show now?
    let coins = 7;
    button.onTap = function () {
      coins = coins + 1;
      label.text = coins;
    };
  40. 40.👆 The user taps the button 6 times. What number does the label show now?
    let stars = 2;
    button.onTap = function () {
      stars = stars + 1;
      label.text = stars;
    };

Answer key

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

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