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App Dev Worksheet: Events

App development lesson 17: Events: on tap, do this · Set 318 · 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 2 times. What number does the label show now?
    let lives = 3;
    button.onTap = function () {
      lives = lives + 2;
      label.text = lives;
    };
  2. 2.True or false: a 5-minute alarm ends is a timer event. (a) False (b) True
  3. 3.👆 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;
    };
  4. 4.👆 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;
    };
  5. 5.👆 A tap handler runs how many times if the user taps 4 times? (a) 0 (b) 8 (c) 4 (d) 1
  6. 6.👆 Code that runs when an event happens is called a ___. (a) header (b) headline (c) handler (d) hashtag
  7. 7.True or false: the user taps Play is a tap event. (a) False (b) True
  8. 8.True or false: the search box changes is a tap event. (a) True (b) False
  9. 9.True or false: a countdown hits zero is a timer event. (a) False (b) True
  10. 10.👆 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
  11. 11.👆 What kind of event is this: the screen first opens? (a) a timer event (b) a text event (c) a load event (d) a tap event
  12. 12.True or false: the user types a letter is a tap event. (a) True (b) False
  13. 13.True or false: the search box changes is a text event. (a) False (b) True
  14. 14.👆 What kind of event is this: the user types a letter? (a) a tap event (b) a timer event (c) a text event (d) a load event
  15. 15.👆 The user taps the button 4 times. What number does the label show now?
    let score = 3;
    button.onTap = function () {
      score = score + 3;
      label.text = score;
    };
  16. 16.👆 What kind of event is this: a 5-minute alarm ends? (a) a load event (b) a text event (c) a timer event (d) a tap event
  17. 17.👆 An event in an app is ___. (a) an app store (b) a colour theme (c) a kind of list (d) something that happens
  18. 18.👆 The user taps the button 5 times. What number does the label show now?
    let likes = 0;
    button.onTap = function () {
      if (likes < 3) {
        likes = likes + 1;
      }
      label.text = likes;
    };
  19. 19.👆 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
  20. 20.👆 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
  21. 21.True or false: a 5-minute alarm ends is a load event. (a) False (b) True
  22. 22.👆 The user taps the button 2 times. What number does the label show now?
    let stars = 9;
    button.onTap = function () {
      stars = stars + 3;
      label.text = stars;
    };
  23. 23.👆 The user types Aman in nameBox and taps the button 1 time. What does the label show?
    button.onTap = function () {
      label.text = "Well done, " + nameBox.text + "!";
    };     (a) Aman (b) Well done! (c) Well done, nameBox.text! (d) Well done, Aman!
  24. 24.👆 The user taps the button 2 times. What number does the label show now?
    let likes = 0;
    button.onTap = function () {
      if (likes < 2) {
        likes = likes + 1;
      }
      label.text = likes;
    };
  25. 25.👆 The user taps the button 5 times. What number does the label show now?
    let coins = 3;
    button.onTap = function () {
      coins = coins + 1;
      label.text = coins;
    };
  26. 26.👆 What kind of event is this: the user presses Save? (a) a load event (b) a text event (c) a timer event (d) a tap event
  27. 27.👆 The user taps the button 6 times. What number does the label show now?
    let points = 4;
    button.onTap = function () {
      points = points + 3;
      label.text = points;
    };
  28. 28.👆 The user taps the button 3 times. What number does the label show now?
    let points = 4;
    button.onTap = function () {
      points = points + 2;
      label.text = points;
    };
  29. 29.👆 What kind of event is this: a countdown hits zero? (a) a tap event (b) a load event (c) a text event (d) a timer event
  30. 30.👆 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) Kabir (b) Welcome, nameBox.text! (c) Welcome! (d) Welcome, Kabir!
  31. 31.👆 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, Arjun! (b) Hello! (c) Arjun (d) Hello, nameBox.text!
  32. 32.👆 The user taps the button 6 times. What number does the label show now?
    let coins = 5;
    button.onTap = function () {
      coins = coins + 5;
      label.text = coins;
    };
  33. 33.👆 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
  34. 34.👆 The user taps the button 6 times. What number does the label show now?
    let coins = 3;
    button.onTap = function () {
      coins = coins + 3;
      label.text = coins;
    };
  35. 35.👆 The user taps the button 2 times. What number does the label show now?
    let lives = 6;
    button.onTap = function () {
      lives = lives + 1;
      label.text = lives;
    };
  36. 36.👆 The user taps the button 2 times. What number does the label show now?
    let score = 9;
    button.onTap = function () {
      score = score + 2;
      label.text = score;
    };
  37. 37.👆 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;
    };
  38. 38.👆 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! (b) Aman (c) Welcome, Aman! (d) Welcome, nameBox.text!
  39. 39.👆 The user taps the button 4 times. What number does the label show now?
    let stars = 4;
    button.onTap = function () {
      stars = stars + 5;
      label.text = stars;
    };
  40. 40.👆 What kind of event is this: the app starts up? (a) a load event (b) a text event (c) a timer event (d) a tap event

Answer key

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

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