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App Dev Worksheet: Events

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

Answer key

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

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