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App Dev Worksheet: Events

App development lesson 17: Events: on tap, do this · Set 257 · 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.👆 What kind of event is this: a countdown hits zero? (a) a load event (b) a timer event (c) a tap event (d) a text event
  2. 2.👆 The user taps the button 6 times. What number does the label show now?
    let points = 10;
    button.onTap = function () {
      points = points + 5;
      label.text = points;
    };
  3. 3.👆 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
  4. 4.👆 The user taps the button 6 times. What number does the label show now?
    let stars = 9;
    button.onTap = function () {
      stars = stars + 1;
      label.text = stars;
    };
  5. 5.👆 The user types Meera 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) Meera (c) Hello! (d) Hello, Meera!
  6. 6.👆 What kind of event is this: a finger hits Like? (a) a tap event (b) a text event (c) a timer event (d) a load event
  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) OFF (b) ON
  8. 8.👆 The user taps the button 2 times. What number does the label show now?
    let stars = 7;
    button.onTap = function () {
      stars = stars + 5;
      label.text = stars;
    };
  9. 9.👆 What kind of event is this: the search box changes? (a) a timer event (b) a tap event (c) a text event (d) a load event
  10. 10.👆 The user taps the button 4 times. What number does the label show now?
    let points = 3;
    button.onTap = function () {
      points = points + 1;
      label.text = points;
    };
  11. 11.👆 A tap handler runs how many times if the user taps 4 times? (a) 8 (b) 0 (c) 1 (d) 4
  12. 12.👆 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;
    };
  13. 13.👆 “On tap → do this” links an event to ___. (a) a font (b) a charger (c) a web address (d) an action
  14. 14.👆 Which of these is an event? (a) the icon colour (b) the font size (c) a list of names (d) the user taps a button
  15. 15.👆 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!
  16. 16.👆 The user taps the button 2 times. What number does the label show now?
    let score = 4;
    button.onTap = function () {
      score = score + 3;
      label.text = score;
    };
  17. 17.👆 What kind of event is this: the user taps Play? (a) a timer event (b) a text event (c) a load event (d) a tap event
  18. 18.👆 What kind of event is this: the user presses Save? (a) a tap event (b) a timer event (c) a text event (d) a load event
  19. 19.👆 The user taps the button 1 times. What number does the label show now?
    let likes = 0;
    button.onTap = function () {
      if (likes < 2) {
        likes = likes + 1;
      }
      label.text = likes;
    };
  20. 20.True or false: a finger hits Like is a load event. (a) False (b) True
  21. 21.👆 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
  22. 22.👆 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
  23. 23.👆 The user types Aman in nameBox and taps the button 1 time. What does the label show?
    button.onTap = function () {
      label.text = "Welcome, " + nameBox.text + "!";
    };     (a) Aman (b) Welcome, nameBox.text! (c) Welcome! (d) Welcome, Aman!
  24. 24.True or false: the user taps Play is a tap event. (a) False (b) True
  25. 25.👆 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! (b) Hello, nameBox.text! (c) Hello, Aman! (d) Aman
  26. 26.👆 The user taps the button 4 times. What number does the label show now?
    let stars = 3;
    button.onTap = function () {
      stars = stars + 1;
      label.text = stars;
    };
  27. 27.👆 The user taps the button 1 times. What number does the label show now?
    let likes = 0;
    button.onTap = function () {
      if (likes < 5) {
        likes = likes + 1;
      }
      label.text = likes;
    };
  28. 28.👆 The user taps the button 2 times. What number does the label show now?
    let likes = 0;
    button.onTap = function () {
      if (likes < 4) {
        likes = likes + 1;
      }
      label.text = likes;
    };
  29. 29.True or false: the screen first opens is a load event. (a) False (b) True
  30. 30.True or false: one second passes is a text event. (a) False (b) True
  31. 31.👆 What kind of event is this: the screen first opens? (a) a timer event (b) a tap event (c) a load event (d) a text event
  32. 32.👆 The user taps the button 5 times. What number does the label show now?
    let likes = 0;
    button.onTap = function () {
      if (likes < 4) {
        likes = likes + 1;
      }
      label.text = likes;
    };
  33. 33.True or false: the user types a letter is a text event. (a) True (b) False
  34. 34.👆 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
  35. 35.True or false: one second passes is a timer event. (a) True (b) False
  36. 36.True or false: a 5-minute alarm ends is a text event. (a) True (b) False
  37. 37.👆 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
  38. 38.👆 Code that runs when an event happens is called a ___. (a) headline (b) hashtag (c) handler (d) header
  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 6 times. What number does the label show now?
    let likes = 0;
    button.onTap = function () {
      if (likes < 2) {
        likes = likes + 1;
      }
      label.text = likes;
    };

Answer key

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

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