App Dev Worksheet: Events

App development lesson 17: Events: on tap, do this · Set 326 · 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 1 times. What number does the label show now?
   let likes = 0;
   button.onTap = function () {
     if (likes < 2) {
       likes = likes + 1;
     }
     label.text = likes;
   };
2. 2.True or false: a 5-minute alarm ends is a timer event. (a) True (b) False
3. 3.True or false: the app starts up is a text event. (a) False (b) True
4. 4.👆 Which of these is an event? (a) a list of names (b) the font size (c) the icon colour (d) the user taps a button
5. 5.👆 The user taps the button 6 times. What number does the label show now?
   let score = 8;
   button.onTap = function () {
     score = score + 4;
     label.text = score;
   };
6. 6.👆 The user taps the button 2 times. What number does the label show now?
   let stars = 5;
   button.onTap = function () {
     stars = stars + 5;
     label.text = stars;
   };
7. 7.👆 What kind of event is this: the app starts up? (a) a timer event (b) a text event (c) a tap event (d) a load event
8. 8.👆 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;
   };
9. 9.👆 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
10. 10.👆 The user taps the button 8 times. What number does the label show now?
    let likes = 0;
    button.onTap = function () {
      if (likes < 3) {
        likes = likes + 1;
      }
      label.text = likes;
    };
11. 11.True or false: the search box changes is a load event. (a) True (b) False
12. 12.👆 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
13. 13.👆 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, nameBox.text! (b) Hello! (c) Aman (d) Hello, Aman!
14. 14.👆 The user taps the button 3 times. What number does the label show now?
    let likes = 0;
    button.onTap = function () {
      if (likes < 4) {
        likes = likes + 1;
      }
      label.text = likes;
    };
15. 15.👆 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
16. 16.True or false: the user taps Play is a text event. (a) False (b) True
17. 17.👆 The user types Aman in nameBox and taps the button 1 time. What does the label show?
    button.onTap = function () {
      label.text = "Hi, " + nameBox.text + "!";
    }; (a) Hi! (b) Hi, Aman! (c) Aman (d) Hi, nameBox.text!
18. 18.True or false: the user presses Save is a timer event. (a) True (b) False
19. 19.👆 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;
    };
20. 20.👆 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) Hello! (c) Riya (d) Hello, Riya!
21. 21.👆 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) Well done! (b) Well done, Arjun! (c) Arjun (d) Well done, nameBox.text!
22. 22.👆 The user taps the button 5 times. What number does the label show now?
    let lives = 0;
    button.onTap = function () {
      lives = lives + 5;
      label.text = lives;
    };
23. 23.👆 “On tap → do this” links an event to ___. (a) an action (b) a charger (c) a font (d) a web address
24. 24.True or false: the screen first opens is a tap event. (a) True (b) False
25. 25.👆 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, nameBox.text! (b) Meera (c) Welcome! (d) Welcome, Meera!
26. 26.👆 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;
    };
27. 27.👆 A tap handler runs how many times if the user taps 4 times? (a) 0 (b) 8 (c) 1 (d) 4
28. 28.👆 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
29. 29.👆 The user types Arjun in nameBox and taps the button 1 time. What does the label show?
    button.onTap = function () {
      label.text = "Welcome, " + nameBox.text + "!";
    }; (a) Arjun (b) Welcome, nameBox.text! (c) Welcome, Arjun! (d) Welcome!
30. 30.👆 The user taps the button 5 times. What number does the label show now?
    let coins = 3;
    button.onTap = function () {
      coins = coins + 3;
      label.text = coins;
    };
31. 31.True or false: the screen first opens is a timer event. (a) False (b) True
32. 32.👆 Code that runs when an event happens is called a ___. (a) header (b) hashtag (c) headline (d) handler
33. 33.👆 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;
    };
34. 34.👆 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
35. 35.👆 What kind of event is this: a 5-minute alarm ends? (a) a text event (b) a tap event (c) a timer event (d) a load event
36. 36.👆 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;
    };
37. 37.👆 The user taps the button 1 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.True or false: a 5-minute alarm ends is a load event. (a) True (b) False
39. 39.👆 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) Arjun (b) Hello! (c) Hello, Arjun! (d) Hello, nameBox.text!
40. 40.👆 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

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