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App Dev Worksheet: Events

App development lesson 17: Events: on tap, do this · Set 259 · 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 = "Well done, " + nameBox.text + "!";
    };     (a) Well done! (b) Arjun (c) Well done, Arjun! (d) Well done, nameBox.text!
  2. 2.👆 Code that runs when an event happens is called a ___. (a) hashtag (b) handler (c) headline (d) header
  3. 3.👆 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!
  4. 4.👆 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;
    };
  5. 5.👆 “On tap → do this” links an event to ___. (a) a charger (b) a font (c) an action (d) a web address
  6. 6.True or false: the user types a letter is a tap event. (a) True (b) False
  7. 7.👆 What kind of event is this: the screen first opens? (a) a tap event (b) a text event (c) a timer event (d) a load event
  8. 8.True or false: one second passes is a timer event. (a) False (b) True
  9. 9.👆 An event in an app is ___. (a) an app store (b) a colour theme (c) a kind of list (d) something that happens
  10. 10.👆 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
  11. 11.True or false: one second passes is a tap event. (a) True (b) False
  12. 12.👆 What kind of event is this: the user presses Save? (a) a load event (b) a timer event (c) a text event (d) a tap event
  13. 13.👆 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
  14. 14.👆 The user taps the button 3 times. What number does the label show now?
    let score = 4;
    button.onTap = function () {
      score = score + 4;
      label.text = score;
    };
  15. 15.True or false: the search box changes is a load event. (a) False (b) True
  16. 16.👆 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
  17. 17.👆 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
  18. 18.👆 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) Welcome, Aman! (b) Aman (c) Welcome! (d) Welcome, nameBox.text!
  19. 19.👆 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;
    };
  20. 20.👆 The user taps the button 2 times. What number does the label show now?
    let stars = 1;
    button.onTap = function () {
      stars = stars + 1;
      label.text = stars;
    };
  21. 21.True or false: the app starts up is a load event. (a) False (b) True
  22. 22.👆 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;
    };
  23. 23.👆 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;
    };
  24. 24.👆 The user types Aman in nameBox and taps the button 1 time. What does the label show?
    button.onTap = function () {
      label.text = "Hi, " + nameBox.text + "!";
    };     (a) Aman (b) Hi, nameBox.text! (c) Hi! (d) Hi, Aman!
  25. 25.👆 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
  26. 26.👆 What kind of event is this: a finger hits Like? (a) a timer event (b) a text event (c) a tap event (d) a load event
  27. 27.True or false: a 5-minute alarm ends is a text event. (a) False (b) True
  28. 28.👆 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) Riya (b) Hi! (c) Hi, Riya! (d) Hi, nameBox.text!
  29. 29.👆 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) Aman (d) Hello, Aman!
  30. 30.True or false: the user presses Save is a load event. (a) True (b) False
  31. 31.👆 The user types Kabir 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, nameBox.text! (b) Kabir (c) Well done! (d) Well done, Kabir!
  32. 32.👆 The user taps the button 4 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.👆 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
  34. 34.👆 What kind of event is this: the app starts up? (a) a timer event (b) a load event (c) a tap event (d) a text event
  35. 35.👆 What kind of event is this: one second passes? (a) a text event (b) a timer event (c) a tap event (d) a load event
  36. 36.👆 The user taps the button 6 times. What number does the label show now?
    let points = 1;
    button.onTap = function () {
      points = points + 1;
      label.text = points;
    };
  37. 37.👆 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
  38. 38.True or false: the user types a letter is a timer event. (a) True (b) False
  39. 39.True or false: a 5-minute alarm ends is a tap event. (a) False (b) True
  40. 40.True or false: the user types a letter is a text event. (a) False (b) True

Answer key

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

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