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App Dev Worksheet: Events

App development lesson 17: Events: on tap, do this · Set 41 · 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 3 times. What number does the label show now?
    let likes = 0;
    button.onTap = function () {
      if (likes < 2) {
        likes = likes + 1;
      }
      label.text = likes;
    };
  2. 2.👆 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
  3. 3.👆 What kind of event is this: the search box changes? (a) a load event (b) a text event (c) a timer event (d) a tap event
  4. 4.👆 What kind of event is this: the screen first opens? (a) a tap event (b) a timer event (c) a load event (d) a text event
  5. 5.👆 The user taps the button 3 times. What number does the label show now?
    let score = 6;
    button.onTap = function () {
      score = score + 2;
      label.text = score;
    };
  6. 6.True or false: the app starts up is a text event. (a) True (b) False
  7. 7.👆 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, nameBox.text! (b) Meera (c) Hi! (d) Hi, Meera!
  8. 8.👆 An event in an app is ___. (a) a kind of list (b) something that happens (c) an app store (d) a colour theme
  9. 9.👆 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
  10. 10.👆 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;
    };
  11. 11.👆 Code that runs when an event happens is called a ___. (a) headline (b) handler (c) hashtag (d) header
  12. 12.👆 What kind of event is this: one second passes? (a) a text event (b) a tap event (c) a load event (d) a timer event
  13. 13.True or false: a 5-minute alarm ends is a load event. (a) False (b) True
  14. 14.👆 The user taps the button 4 times. What number does the label show now?
    let stars = 2;
    button.onTap = function () {
      stars = stars + 2;
      label.text = stars;
    };
  15. 15.👆 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
  16. 16.👆 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, nameBox.text! (b) Riya (c) Hi! (d) Hi, Riya!
  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) OFF (b) ON
  18. 18.👆 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) Arjun (b) Hi, nameBox.text! (c) Hi! (d) Hi, Arjun!
  19. 19.True or false: one second passes is a timer event. (a) False (b) True
  20. 20.True or false: a countdown hits zero is a tap event. (a) True (b) False
  21. 21.👆 The user types Meera in nameBox and taps the button 1 time. What does the label show?
    button.onTap = function () {
      label.text = "Welcome, " + nameBox.text + "!";
    };     (a) Welcome! (b) Welcome, Meera! (c) Meera (d) Welcome, nameBox.text!
  22. 22.👆 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;
    };
  23. 23.👆 The user taps the button 2 times. What number does the label show now?
    let score = 0;
    button.onTap = function () {
      score = score + 3;
      label.text = score;
    };
  24. 24.👆 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
  25. 25.👆 What kind of event is this: a countdown hits zero? (a) a text event (b) a timer event (c) a tap event (d) a load event
  26. 26.True or false: the user presses Save is a text event. (a) False (b) True
  27. 27.True or false: a 5-minute alarm ends is a timer event. (a) False (b) True
  28. 28.👆 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, Arjun! (c) Hello! (d) Arjun
  29. 29.👆 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) OFF (b) ON
  30. 30.👆 The user taps the button 3 times. What number does the label show now?
    let points = 0;
    button.onTap = function () {
      points = points + 3;
      label.text = points;
    };
  31. 31.👆 The user taps the button 6 times. What number does the label show now?
    let score = 9;
    button.onTap = function () {
      score = score + 4;
      label.text = score;
    };
  32. 32.👆 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
  33. 33.True or false: the search box changes is a text event. (a) False (b) True
  34. 34.👆 The user taps the button 2 times. What number does the label show now?
    let coins = 0;
    button.onTap = function () {
      coins = coins + 1;
      label.text = coins;
    };
  35. 35.👆 What kind of event is this: the app starts up? (a) a timer event (b) a text event (c) a tap event (d) a load event
  36. 36.True or false: the app starts up is a timer event. (a) False (b) True
  37. 37.👆 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
  38. 38.True or false: the app starts up is a load event. (a) False (b) True
  39. 39.👆 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;
    };
  40. 40.👆 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;
    };

Answer key

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

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