App Dev Worksheet: Events

App development lesson 17: Events: on tap, do this · Set 232 · 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.

NameDateTime takenScore ___ / 40

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

Answer key

4
an action
False
2
OFF
the user taps a button
False
False
ON
True
True
Welcome, Zoya!
ON
False
ON
Hello, Kabir!
a load event
False
23
something that happens
2
False
12
a tap event
handler
False
True
a text event
True
21
False
33
True
3
16
Hello, Aman!
a text event
False
OFF
5

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