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App Dev Worksheet: Events

App development lesson 17: Events: on tap, do this · Set 135 · 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 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
  2. 2.👆 The user taps the button 2 times. What number does the label show now?
    let points = 0;
    button.onTap = function () {
      points = points + 5;
      label.text = points;
    };
  3. 3.👆 An event in an app is ___. (a) a kind of list (b) a colour theme (c) something that happens (d) an app store
  4. 4.👆 What kind of event is this: a 5-minute alarm ends? (a) a load event (b) a text event (c) a timer event (d) a tap event
  5. 5.True or false: one second passes is a tap event. (a) True (b) False
  6. 6.👆 The user taps the button 2 times. What number does the label show now?
    let lives = 10;
    button.onTap = function () {
      lives = lives + 4;
      label.text = lives;
    };
  7. 7.👆 The user taps the button 6 times. What number does the label show now?
    let score = 9;
    button.onTap = function () {
      score = score + 1;
      label.text = score;
    };
  8. 8.👆 Code that runs when an event happens is called a ___. (a) headline (b) header (c) handler (d) hashtag
  9. 9.True or false: the user types a letter is a text event. (a) False (b) True
  10. 10.👆 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
  11. 11.👆 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
  12. 12.👆 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
  13. 13.True or false: the app starts up is a load event. (a) True (b) False
  14. 14.👆 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
  15. 15.👆 The user taps the button 2 times. What number does the label show now?
    let lives = 7;
    button.onTap = function () {
      lives = lives + 2;
      label.text = lives;
    };
  16. 16.👆 The user taps the button 3 times. What number does the label show now?
    let lives = 7;
    button.onTap = function () {
      lives = lives + 5;
      label.text = lives;
    };
  17. 17.👆 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;
    };
  18. 18.True or false: a 5-minute alarm ends is a tap event. (a) True (b) False
  19. 19.👆 The user taps the button 2 times. What number does the label show now?
    let lives = 2;
    button.onTap = function () {
      lives = lives + 5;
      label.text = lives;
    };
  20. 20.👆 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) Hello, Arjun! (b) Arjun (c) Hello! (d) Hello, nameBox.text!
  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 taps the button 6 times. What number does the label show now?
    let coins = 2;
    button.onTap = function () {
      coins = coins + 1;
      label.text = coins;
    };
  23. 23.👆 The user taps the button 2 times. What number does the label show now?
    let score = 5;
    button.onTap = function () {
      score = score + 3;
      label.text = score;
    };
  24. 24.👆 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! (b) Meera (c) Well done, nameBox.text! (d) Well done, Meera!
  25. 25.True or false: the user taps Play is a tap event. (a) False (b) True
  26. 26.True or false: a finger hits Like is a timer event. (a) True (b) False
  27. 27.👆 What kind of event is this: a finger hits Like? (a) a text event (b) a tap event (c) a load event (d) a timer event
  28. 28.👆 What kind of event is this: the app starts up? (a) a text event (b) a timer event (c) a load event (d) a tap event
  29. 29.👆 The user taps the button 1 times. What number does the label show now?
    let likes = 0;
    button.onTap = function () {
      if (likes < 3) {
        likes = likes + 1;
      }
      label.text = likes;
    };
  30. 30.👆 The user types Riya in nameBox and taps the button 1 time. What does the label show?
    button.onTap = function () {
      label.text = "Hello, " + nameBox.text + "!";
    };     (a) Hello, nameBox.text! (b) Hello! (c) Riya (d) Hello, Riya!
  31. 31.👆 Which of these is an event? (a) the font size (b) a list of names (c) the icon colour (d) the user taps a button
  32. 32.👆 The user taps the button 2 times. What number does the label show now?
    let score = 10;
    button.onTap = function () {
      score = score + 4;
      label.text = score;
    };
  33. 33.👆 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, nameBox.text! (d) Hi!
  34. 34.👆 The user taps the button 5 times. What number does the label show now?
    let likes = 0;
    button.onTap = function () {
      if (likes < 2) {
        likes = likes + 1;
      }
      label.text = likes;
    };
  35. 35.👆 The user types Aman in nameBox and taps the button 1 time. What does the label show?
    button.onTap = function () {
      label.text = "Hello, " + nameBox.text + "!";
    };     (a) Hello, Aman! (b) Aman (c) Hello! (d) Hello, nameBox.text!
  36. 36.👆 The user taps the button 2 times. What number does the label show now?
    let lives = 10;
    button.onTap = function () {
      lives = lives + 1;
      label.text = lives;
    };
  37. 37.👆 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;
    };
  38. 38.👆 The user taps the button 5 times. What number does the label show now?
    let score = 9;
    button.onTap = function () {
      score = score + 5;
      label.text = score;
    };
  39. 39.True or false: the user types a letter is a tap event. (a) False (b) True
  40. 40.True or false: a countdown hits zero is a timer event. (a) True (b) False

Answer key

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

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