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App Dev Worksheet: Events

App development lesson 17: Events: on tap, do this · Set 236 · 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 points = 0;
    button.onTap = function () {
      points = points + 2;
      label.text = points;
    };
  2. 2.👆 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
  3. 3.👆 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;
    };
  4. 4.👆 What kind of event is this: the user presses Save? (a) a load event (b) a text event (c) a tap event (d) a timer event
  5. 5.👆 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;
    };
  6. 6.👆 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
  7. 7.👆 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
  8. 8.True or false: the app starts up is a tap event. (a) True (b) False
  9. 9.👆 An event in an app is ___. (a) a kind of list (b) an app store (c) a colour theme (d) something that happens
  10. 10.👆 The user taps the button 4 times. What number does the label show now?
    let stars = 10;
    button.onTap = function () {
      stars = stars + 2;
      label.text = stars;
    };
  11. 11.👆 What kind of event is this: a countdown hits zero? (a) a text event (b) a timer event (c) a load event (d) a tap event
  12. 12.True or false: the user presses Save is a timer event. (a) True (b) False
  13. 13.👆 The user taps the button 3 times. What number does the label show now?
    let lives = 4;
    button.onTap = function () {
      lives = lives + 4;
      label.text = lives;
    };
  14. 14.👆 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, nameBox.text! (b) Riya (c) Hello! (d) Hello, Riya!
  15. 15.True or false: the user types a letter is a load event. (a) False (b) True
  16. 16.👆 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, Zoya! (b) Hello! (c) Zoya (d) Hello, nameBox.text!
  17. 17.👆 The user taps the button 6 times. What number does the label show now?
    let stars = 2;
    button.onTap = function () {
      stars = stars + 1;
      label.text = stars;
    };
  18. 18.👆 What kind of event is this: the user types a letter? (a) a load event (b) a timer event (c) a text event (d) a tap event
  19. 19.👆 What kind of event is this: a finger hits Like? (a) a tap event (b) a load event (c) a text event (d) a timer event
  20. 20.True or false: the user types a letter is a text event. (a) False (b) True
  21. 21.👆 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) Hello, nameBox.text! (b) Hello! (c) Hello, Kabir! (d) Kabir
  22. 22.👆 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
  23. 23.True or false: a finger hits Like is a tap event. (a) True (b) False
  24. 24.👆 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) ON (b) OFF
  25. 25.👆 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;
    };
  26. 26.👆 The user taps the button 4 times. What number does the label show now?
    let stars = 5;
    button.onTap = function () {
      stars = stars + 3;
      label.text = stars;
    };
  27. 27.👆 The user taps the button 2 times. What number does the label show now?
    let score = 5;
    button.onTap = function () {
      score = score + 2;
      label.text = score;
    };
  28. 28.👆 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) Arjun (b) Well done, Arjun! (c) Well done, nameBox.text! (d) Well done!
  29. 29.👆 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
  30. 30.👆 What kind of event is this: the user taps Play? (a) a text event (b) a timer event (c) a load event (d) a tap event
  31. 31.👆 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) Well done, nameBox.text! (b) Well done! (c) Aman (d) Well done, Aman!
  32. 32.👆 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;
    };
  33. 33.True or false: the search box changes is a tap event. (a) False (b) True
  34. 34.True or false: a 5-minute alarm ends is a text event. (a) True (b) False
  35. 35.True or false: the screen first opens is a timer event. (a) True (b) False
  36. 36.True or false: the search box changes is a text event. (a) True (b) False
  37. 37.👆 The user taps the button 4 times. What number does the label show now?
    let score = 0;
    button.onTap = function () {
      score = score + 2;
      label.text = score;
    };
  38. 38.👆 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
  39. 39.👆 The user taps the button 4 times. What number does the label show now?
    let score = 1;
    button.onTap = function () {
      score = score + 5;
      label.text = score;
    };
  40. 40.👆 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

Answer key

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

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