Original subtitles

0 Now we can see that in the final version of our app when we click on either of these icon cards, they 1

actually change color to show that they've been interacted with and they've been selected. But currently 2

our cards don't really do anything when we click on it. And we can see that our cards or what it's based on 3

be at the iconContent or the reusableCard, 4

none of them actually can take any user input. They don't have an onPressed or an onTap or anything 5

of the sort. 6

So let's fix this in this lesson and let's make our icon cards interactive. Now one way of doing this 7

is we could wrap our reusableCard in a flat button. So we could hold down OPTION or ALT and hit ENTER. 8

Then we could wrap with the new widget and the widget would be a flat button. 9

And this of course will give us access to that crucial onPressed which allows us to tap into the moment 10

when a user actually presses on either of these reusable cards, and we'll be able to change the color 11

that way. 12

Now the problem with flat button is if I hit save right now, you'll be at to see that it actually affects 13

the styling of our card. 14

It's trying to change the margin and various other styles of its children. 15

So it's quite an opinionated widget. 16

And the use case for a flat button is you want to be a to implement the style of a material flat button, 17

and that includes various colors various themes and its appearance. 18

But in our case all that we actually need is just the ability to detect a touch on our already pretty 19

much well styled reusable card. 20

So instead of a flat button, we can use something called a gesture detector. A gesture detector does pretty 21

much what it says on the tin, 22

right? 23

It detects gestures and the gestures it can detect are things like onTap, which is the same as onPressed, 24

but it can also detect a whole lot more. 25

So for example it can detect a long press or drag or force press and a whole lot more. 26

All that this widget is concerned with is detecting gestures. 27

It doesn't try to force any sort of styling or appearance or animations onto the children widgets. 28

So this is a very pure way of detecting when a user interacts with a widget of ours. 29

So by having our reusable card as a child of our gesture detector, we can now start tapping into the 30

gestures that it can detect. 31

So for example, onTap is your classic single tap on the screen. 32

So it's the same as the onPressed of a flat button. Or we can detect a vertical drag, horizontal drag, 33

double tap, force press, 34

whole lot more. 35

But all we need right now is the onTap gesture detector. 36

So I'm going to add our classic anonymous callback and inside here, I'm just going to print that the 37

male card was pressed. And now if we hit save and go into our app making sure that our run tab is showing, 38

and if I click on that male button, you can see that we get 'Male card was pressed' every single time I 39

press on it. 40

So it works just like a flat button 41

and it's really easy to implement. Now that we've got our gesture detector, we're able to detect when 42

a user actually clicks on our cards, be it male or female. 43

And what we want to happen is when we click on the male card, we want it to change color to show that 44

it has been selected. 45

And in order to do this we have to, of course, use our set state. 46

And we're going to update the color property of our reusable card. 47

This is why we have a stateful widget here so that we can actually change the state of our cards. The 48

way that we're going to do this is our cards 49

will start out with a slightly darker background color. 50

And when it's tapped, it will change to have the same color as the rest of the card. 51

So the active color. 52

So firstly up here in our constants, we're going to have a activeCardColor and we're also going to 53

create a new constant for the inactiveCardColor. And the inactiveCardColor is also going to be a 54

custom color and it's going to have a hex value of 0xFF111328 . 55

And you can see over here in the gutter that it's just a little bit darker from the activeCardColor, 56

but it's not exactly the same as the main background color. 57

It's just a little bit lighter. 58

And if I go ahead and simply change the color for the male card for example to the inactive card color 59

and hit save, then you can see that it's just a little bit darker than the active color but it's not 60

quite the same as the background color so it doesn't just blend in. 61

So you can still see that there is a card here but it's obviously not selected and not activated, whereas 62

this card looks the same as the other cards. 63

So it looks like it's the activated or the selected card. 64

So this is the look that we're going for. 65

And both cards should start out having the inactive card color but when one of them is tapped on, then 66

we should change that color to the active card color. 67

So to do this we're going to go into our state widget which is mutable so its properties can change 68

and mutate, so the properties for this class don't have to be final. 69

They can be variables that can change. 70

So the first one we're going to create is going to be of type color. 71

And it's going to be called maleCardColor and it's going to be set to equal the inactiveCardColor. 72

So this is going to be the starting value for both the male card color and also the femaleCardColor. 73

And we're going to be using this variables, femaleCardColor and maleCardColor inside our reusable 74

cards. 75

So this way, we're able to selectively change the color for these cards depending on which one was selected. 76

Now in order to make our cards change onTap, we're going to create a method called updateColor. 77

And this is going to take an input which is going to somehow tell us which gender was clicked on. 78

So it's going to be called gender and it's simply just going to be an integer right now. 79

And we could say that maybe for example, if we pass in one then that equals male and if we pass and two 80

then that equals female. Inside this method, we're going to use an IF statement to check to see if the 81

gender is equal to 1. 82

So if we pass in the value one, then this means that it was the male card that was pressed. 83

Then in this case we're going to check to see if the maleCardColor is currently equal to an inactive 84

CardColor. 85

Well in that case, we're going to change it to the activeCardColor. 86

So we're going to toggle the color of the card. 87

But if it was already in the activeCardColor, then we're going to change it to the opposite which is 88

going to be the inactiveCardColor. 89

So now if we go into our onTap and instead of printing the 'Male card was pressed', we use a set state 90

to update the state of our maleCardColor property which is used to determine the color. 91

Then we can call that method that we created just now updateColor. 92

And we said that the number 1 was going to represent the male gender. 93

So now if we hit save and you can see that my card both start out being the inactive color. 94

So they're not quite the same as this one but as soon as I click on it it changes to the active color. 95

And that's because I'm passing in 1 into this method and while maleCardColor started out being inactive, 96

as soon as it detects the touch, then it'll update it to the active color. 97

But right now it's the active color 98

so if I click on it again, it'll go back to the inactive color. 99

So this way we can toggle the background color of the card to be able to represent when something is selected 100

or not. 101

So let's go ahead and do the same for the female card. All we need to do is to add another ELSE, if the 102

gender is not equal to one or if you want to have more than one gender in your app, then you might simply 103

just add an IF statement that checks if gender equals 2. 104

So we'll say that 2 is equal to female card pressed. 105

And in this case, we're pretty much going to do the opposite. 106

So we're going to check to see if the femaleCardColor starts out being inactive. 107

If so, we're going to change it to the active color but otherwise we're going to toggle it to inactive. 108

So now inside our female card, we're going to also wrap our reusable card inside a new gesture detector. 109

And this is also going to have a onTap which is an anonymous function that gets triggered when the 110

tap gets detected. 111

And when that happens, we're going to call set state to update the color and we're going to pass in the 112

gender as number two, to say that the female card got pressed. So let's hit save 113

and let's check out our app. 114

So now when I click the male card, the male card lights up and I can deactivate it by clicking on it again. 115

And if I click on the female card, the female card gets activated. 116

So now we're able to select a gender in our BMI calculator. 117

Now at the moment though when I click on the male card when the female card is selected, the female card 118

stays selected 119

right? 120

But let's say that I made a mistake and I actually meant to select this one, then when I click on it 121

it should turn off this one because they probably shouldn't both be selected at the same time. 122

So how can we do this? 123

Well it's pretty easy although it's going to add to our already super wordy method. 124

Don't worry, we're gonna make it a lot easier on the eye a little bit later on. 125

But we're first mapping out the functionality so we understand what's going on. 126

So if updateColor is called and it was the male card that was pressed, so gender is one, then we're going 127

to not only switch on the maleCardColor, but we're also going to switch off the femaleCardColor. So 128

we're gonna change this to inactiveCardColor. And the opposite is also true when the female card gets 129

pressed, 130

then we're going to switch off the maleCardColor. 131

So we're going to change that to inactive. 132

And now let's hit save and you can see that if I click on the male card, the female card switches off. 133

If I click on the female card, the male cuts which is off. 134

And this behavior makes a lot more sense. Now in the coming lessons, 135

we're going to simplify all of this logic to something that's a lot shorter and more succinct and easier 136

on the eyes. 137

Because at the moment, it's super wordy and very confusing what's actually going on. 138

But in order to achieve this, we need to learn a little bit more about Dart. 139

So in the next lesson we're going to talk about Dart enums. For all of that and more, 140

I see you there.