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App Dev Worksheet: Events

App development lesson 17: Events: on tap, do this · Set 235 · 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.👆 An event in an app is ___. (a) an app store (b) a kind of list (c) a colour theme (d) something that happens
  2. 2.👆 What kind of event is this: a 5-minute alarm ends? (a) a tap event (b) a timer event (c) a text event (d) a load event
  3. 3.👆 The user types Kabir in nameBox and taps the button 1 time. What does the label show?
    button.onTap = function () {
      label.text = "Hello, " + nameBox.text + "!";
    };     (a) Hello! (b) Hello, Kabir! (c) Hello, nameBox.text! (d) Kabir
  4. 4.👆 The user taps the button 6 times. What number does the label show now?
    let points = 9;
    button.onTap = function () {
      points = points + 2;
      label.text = points;
    };
  5. 5.True or false: a countdown hits zero is a text event. (a) False (b) True
  6. 6.👆 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;
    };
  7. 7.👆 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) OFF (b) ON
  8. 8.👆 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! (b) Hi, Riya! (c) Hi, nameBox.text! (d) Riya
  9. 9.👆 Code that runs when an event happens is called a ___. (a) headline (b) hashtag (c) handler (d) header
  10. 10.👆 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
  11. 11.True or false: a countdown hits zero is a timer event. (a) False (b) True
  12. 12.👆 The user taps the button 4 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 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;
    };
  14. 14.👆 What kind of event is this: the app starts up? (a) a timer event (b) a tap event (c) a text event (d) a load event
  15. 15.👆 What kind of event is this: one second passes? (a) a load event (b) a tap event (c) a text event (d) a timer event
  16. 16.👆 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
  17. 17.👆 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
  18. 18.👆 Which of these is an event? (a) the font size (b) a list of names (c) the user taps a button (d) the icon colour
  19. 19.👆 What kind of event is this: the user taps Play? (a) a text event (b) a tap event (c) a load event (d) a timer event
  20. 20.👆 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, Zoya! (b) Welcome! (c) Zoya (d) Welcome, nameBox.text!
  21. 21.👆 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;
    };
  22. 22.👆 What kind of event is this: a finger hits Like? (a) a text event (b) a load event (c) a tap event (d) a timer event
  23. 23.👆 What kind of event is this: the user types a letter? (a) a load event (b) a text event (c) a timer event (d) a tap event
  24. 24.True or false: the app starts up is a load event. (a) True (b) False
  25. 25.True or false: the screen first opens is a tap event. (a) False (b) True
  26. 26.👆 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
  27. 27.👆 The user taps the button 4 times. What number does the label show now?
    let stars = 10;
    button.onTap = function () {
      stars = stars + 5;
      label.text = stars;
    };
  28. 28.👆 The user taps the button 3 times. What number does the label show now?
    let coins = 5;
    button.onTap = function () {
      coins = coins + 1;
      label.text = coins;
    };
  29. 29.True or false: the user types a letter is a load event. (a) True (b) False
  30. 30.True or false: the app starts up is a tap event. (a) False (b) True
  31. 31.👆 The user taps the button 6 times. What number does the label show now?
    let stars = 5;
    button.onTap = function () {
      stars = stars + 3;
      label.text = stars;
    };
  32. 32.True or false: the search box changes is a tap event. (a) False (b) True
  33. 33.👆 The user taps the button 6 times. What number does the label show now?
    let coins = 7;
    button.onTap = function () {
      coins = coins + 4;
      label.text = coins;
    };
  34. 34.👆 The user taps the button 3 times. What number does the label show now?
    let likes = 0;
    button.onTap = function () {
      if (likes < 3) {
        likes = likes + 1;
      }
      label.text = likes;
    };
  35. 35.👆 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;
    };
  36. 36.👆 The user taps the button 7 times. What number does the label show now?
    let likes = 0;
    button.onTap = function () {
      if (likes < 2) {
        likes = likes + 1;
      }
      label.text = likes;
    };
  37. 37.👆 The user taps the button 6 times. What number does the label show now?
    let score = 8;
    button.onTap = function () {
      score = score + 5;
      label.text = score;
    };
  38. 38.👆 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;
    };
  39. 39.👆 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) Arjun (c) Hi, Arjun! (d) Hi!
  40. 40.True or false: a finger hits Like is a load event. (a) False (b) True

Answer key

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

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