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App Dev Worksheet: Events

App development lesson 17: Events: on tap, do this · Set 251 · 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: the user presses Save? (a) a timer event (b) a tap event (c) a load event (d) a text event
  2. 2.👆 The user taps the button 8 times. What number does the label show now?
    let likes = 0;
    button.onTap = function () {
      if (likes < 2) {
        likes = likes + 1;
      }
      label.text = likes;
    };
  3. 3.👆 An event in an app is ___. (a) an app store (b) something that happens (c) a colour theme (d) a kind of list
  4. 4.👆 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;
    };
  5. 5.👆 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;
    };
  6. 6.👆 The user taps the button 7 times. What number does the label show now?
    let likes = 0;
    button.onTap = function () {
      if (likes < 5) {
        likes = likes + 1;
      }
      label.text = likes;
    };
  7. 7.👆 The user taps the button 2 times. What number does the label show now?
    let score = 4;
    button.onTap = function () {
      score = score + 4;
      label.text = score;
    };
  8. 8.👆 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
  9. 9.👆 The user taps the button 2 times. What number does the label show now?
    let lives = 6;
    button.onTap = function () {
      lives = lives + 5;
      label.text = lives;
    };
  10. 10.True or false: one second passes is a text event. (a) True (b) False
  11. 11.👆 A tap handler runs how many times if the user taps 4 times? (a) 8 (b) 4 (c) 0 (d) 1
  12. 12.👆 What kind of event is this: a 5-minute alarm ends? (a) a tap event (b) a timer event (c) a text event (d) a load event
  13. 13.👆 The user taps the button 6 times. What number does the label show now?
    let stars = 8;
    button.onTap = function () {
      stars = stars + 2;
      label.text = stars;
    };
  14. 14.👆 The user types Kabir in nameBox and taps the button 1 time. What does the label show?
    button.onTap = function () {
      label.text = "Hello, " + nameBox.text + "!";
    };     (a) Kabir (b) Hello, Kabir! (c) Hello, nameBox.text! (d) Hello!
  15. 15.👆 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, nameBox.text! (b) Hello! (c) Hello, Zoya! (d) Zoya
  16. 16.👆 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) Meera (c) Welcome, nameBox.text! (d) Welcome, Meera!
  17. 17.True or false: one second passes is a timer event. (a) True (b) False
  18. 18.True or false: the user presses Save is a timer event. (a) False (b) True
  19. 19.True or false: the user presses Save is a tap event. (a) False (b) True
  20. 20.👆 The user taps the button 6 times. What number does the label show now?
    let score = 8;
    button.onTap = function () {
      score = score + 1;
      label.text = score;
    };
  21. 21.👆 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, Kabir! (b) Welcome, nameBox.text! (c) Welcome! (d) Kabir
  22. 22.👆 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
  23. 23.👆 What kind of event is this: the search box changes? (a) a timer event (b) a load event (c) a tap event (d) a text event
  24. 24.👆 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
  25. 25.👆 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
  26. 26.👆 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
  27. 27.True or false: the search box changes is a text event. (a) False (b) True
  28. 28.👆 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;
    };
  29. 29.👆 The user types Riya 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) Well done! (c) Well done, Riya! (d) Riya
  30. 30.👆 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;
    };
  31. 31.True or false: the app starts up is a tap event. (a) True (b) False
  32. 32.👆 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;
    };
  33. 33.True or false: the screen first opens is a load event. (a) True (b) False
  34. 34.👆 The user types Riya in nameBox and taps the button 1 time. What does the label show?
    button.onTap = function () {
      label.text = "Hello, " + nameBox.text + "!";
    };     (a) Hello! (b) Riya (c) Hello, Riya! (d) Hello, nameBox.text!
  35. 35.👆 Code that runs when an event happens is called a ___. (a) handler (b) headline (c) hashtag (d) header
  36. 36.True or false: the user taps Play is a text event. (a) False (b) True
  37. 37.👆 The user taps the button 4 times. What number does the label show now?
    let score = 0;
    button.onTap = function () {
      score = score + 4;
      label.text = score;
    };
  38. 38.👆 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
  39. 39.👆 The user taps the button 3 times. What number does the label show now?
    let points = 3;
    button.onTap = function () {
      points = points + 4;
      label.text = points;
    };
  40. 40.👆 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;
    };

Answer key

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

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