App Dev Worksheet: Events

App development lesson 17: Events: on tap, do this · Set 220 · 40 questions

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.

1. 1.👆 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;
   };
2. 2.👆 The user taps the button 6 times. What number does the label show now?
   let lives = 8;
   button.onTap = function () {
     lives = lives + 4;
     label.text = lives;
   };
3. 3.True or false: one second passes is a tap event. (a) True (b) False
4. 4.True or false: a countdown hits zero is a load event. (a) True (b) False
5. 5.👆 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) OFF (b) ON
6. 6.👆 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;
   };
7. 7.👆 What kind of event is this: a countdown hits zero? (a) a timer event (b) a tap event (c) a load event (d) a text event
8. 8.👆 The user taps the button 1 times. What number does the label show now?
   let likes = 0;
   button.onTap = function () {
     if (likes < 4) {
       likes = likes + 1;
     }
     label.text = likes;
   };
9. 9.👆 A tap handler runs how many times if the user taps 4 times? (a) 0 (b) 1 (c) 4 (d) 8
10. 10.👆 The user taps the button 4 times. What number does the label show now?
    let stars = 1;
    button.onTap = function () {
      stars = stars + 4;
      label.text = stars;
    };
11. 11.True or false: the user types a letter is a text event. (a) False (b) True
12. 12.👆 Code that runs when an event happens is called a ___. (a) hashtag (b) header (c) headline (d) handler
13. 13.👆 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
14. 14.True or false: the user presses Save is a text event. (a) True (b) False
15. 15.👆 What kind of event is this: the screen first opens? (a) a load event (b) a timer event (c) a text event (d) a tap event
16. 16.👆 Which of these is an event? (a) the icon colour (b) the font size (c) a list of names (d) the user taps a button
17. 17.👆 “On tap → do this” links an event to ___. (a) a charger (b) a font (c) a web address (d) an action
18. 18.👆 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;
    };
19. 19.👆 The user taps the button 4 times. What number does the label show now?
    let points = 7;
    button.onTap = function () {
      points = points + 1;
      label.text = points;
    };
20. 20.👆 The user taps the button 4 times. What number does the label show now?
    let lives = 0;
    button.onTap = function () {
      lives = lives + 2;
      label.text = lives;
    };
21. 21.True or false: a finger hits Like is a timer event. (a) False (b) True
22. 22.👆 What kind of event is this: the user taps Play? (a) a timer event (b) a load event (c) a tap event (d) a text event
23. 23.👆 The user types Meera 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, Meera! (b) Meera (c) Well done! (d) Well done, nameBox.text!
24. 24.👆 An event in an app is ___. (a) something that happens (b) an app store (c) a kind of list (d) a colour theme
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.👆 The user taps the button 2 times. What number does the label show now?
    let lives = 4;
    button.onTap = function () {
      lives = lives + 4;
      label.text = lives;
    };
27. 27.👆 The user taps the button 3 times. What number does the label show now?
    let points = 8;
    button.onTap = function () {
      points = points + 4;
      label.text = points;
    };
28. 28.True or false: the search box changes is a load event. (a) False (b) True
29. 29.👆 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;
    };
30. 30.True or false: a 5-minute alarm ends is a tap event. (a) True (b) False
31. 31.👆 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) OFF (b) ON
32. 32.👆 What kind of event is this: one second passes? (a) a load event (b) a timer event (c) a tap event (d) a text event
33. 33.👆 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;
    };
34. 34.👆 The user taps the button 6 times. What number does the label show now?
    let score = 0;
    button.onTap = function () {
      score = score + 5;
      label.text = score;
    };
35. 35.👆 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;
    };
36. 36.👆 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;
    };
37. 37.True or false: a countdown hits zero is a timer event. (a) False (b) True
38. 38.👆 What kind of event is this: a finger hits Like? (a) a load event (b) a text event (c) a tap event (d) a timer event
39. 39.True or false: the user taps Play is a timer event. (a) True (b) False
40. 40.👆 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, Aman! (b) Aman (c) Hello! (d) Hello, nameBox.text!

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