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App Dev Worksheet: Events

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

Answer key

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

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