Original subtitles

0 Now you can see that even though all the cards look the same which is how we're able to use our reusable 1

card to style each of them and have them laid out using our expanded widgets, but their content are all 2

different. And usually in Flutter when we're using the widgets that Flutter have created, they tend to 3

address this by having a child property. 4

So for example the expanded widget will have a child or the container will have a child. 5

And this allows us to reuse the same widget 6

but to add custom content for each of these widget that we use. 7

So let's go ahead and create a new child property so that we can do the same with our custom reusable 8

Card. First things first, 9

we're going to create our custom child property and we're gonna call it cardChild. 10

Also this has to be final because our widget is immutable. 11

And then this is going to have the type of widget and it's going to be called cardChild. 12

Well there's a new property but we now have to initialize it because we're getting an error that tells 13

us the final variable car child must be initialized. 14

So we do that in here. 15

Now I don't think the child property should be required. 16

So we don't need to add the required annotation. All we need to do is just write this.cardChild. 17

So that means if we create a new reusableCard, then we can if we wish to add a child to go inside our 18

widget. 19

But if we don't need to have any content, then we can simply just have it as is. Now the final thing is 20

where is this child gonna be placed inside our widget tree? Well it's going to be a child of our container. 21

So we can tap into the container's child property and we're gonna say that whatever cardChild gets passed 22

into this reusableCard will be the child of our container, and that's it. 23

That's all we need to do. 24

Now that we've updated our reusableCard, then it's time to actually add some content. 25

And the first one that we're going to address are these cards that will allow the user to choose their 26

gender. 27

So we've got a icon which comes from a font awesome Flutter package. 28

And then we've got a little bit of text underneath just as a description. 29

So let's get started by customizing our reusableCards at the top row and get the styling down first 30

before we code up any of the functionality. 31

So first things first, we need to get some icons from font awesome. 32

We're going to need the font_ 33

awesome_flutter package. 34

So let's go ahead and add this to our pubspec.yaml which at the moment doesn't really contain 35

any custom packages. 36

So right below where we have cupertino icons, we're going to add in font_awesome_flutter. And I'm just 37

going to paste that in here. And then we're going to add the obligatory YAML markup which is going 38

to include a colon here and I'm going to add a caret sign up here as well. 39

And this way we show that we're happy with it using any major versions of font_awesome_flutter that are 40

8.something.something but we're not going to go beyond eight to nine. 41

So now that we've updated our YAML, we're going to click on packages.get and we're going to import 42

the package into our import page. 43

So we're going to import the font awesome package and then we're going to be able to use it inside our 44

reusableCard. So first things first, we're going to target our first card here which is going to look 45

something like this. 46

So we'll have everything centered in the middle of the card and we're going to have our Mars icon from 47

font awesome and a little bit of text below. 48

So this is probably easily achieved using a column as a child. 49

So let's go ahead and add that cardChild which we created earlier on as a property, and the cardChild 50

is going to be a column which is going to have two children. And those two children are going to be firstly 51

a icon which is going to be created from a font awesome icon. And the one that we need is the one called 52

mars, which is generally the male symbol. Now that we have the icon in, 53

I'm going to increase the size of the icon to 80, just make it a lot larger than how it normally is. 54

And then I'm going to add a little bit of a gap between the icon and the text. And to do that we usually 55

use a sizedBox. And we can provide a custom height property to specify how much distance we want between 56

the icon and the text. 57

And in this case I'm going to pick 15. And now finally we can add a text widget and it's just going to 58

say the word male in all caps. And then I'm just going to add a little bit of style which is going to 59

be a text style widget and all I'm going to do is increase the font size to 18 and also change the font 60

color to a custom color and it's going to be 0xFF, so fully opaque, 8D8E98. And you'll see that this 61

is kind of this light gray color, and again all of these colors came from the original Dribbble design 62

just by using the color picker tool. So let's add in all the commas so that when we hit save, Dart willl 63

reformat our code for us. Now at this point if you look at our design, you'll see that we're not actually 64

pulling in the font awesome icon, and this is because after every time you add a new package and you run 65

packages.get, it's actually a good idea to stop the app and run it from scratch so that we do a cold 66

restart and it can incorporate all the things we need, namely the font awesome icons. And now you can see 67

the actual icon that we want onscreen but our column, 68

that is the child of this reusableCard, 69

it's kind of all over the place. But we can add a column property if you remember from before, something 70

called mainAxisAlignment to actually center our column in the parent. 71

So if we hit save 72

now you can see that our icon and our text will go right in the middle of the parent which is the reusable 73

Card. 74

Now we know that in the final design, we're going to have two cards that essentially look pretty much 75

the same. 76

They both have an icon and a bit of text and the styling are exactly the same. 77

So it makes sense then for us to actually reuse this part where we're creating the icon and the gap 78

and the text widget so that we can extract it as a separate widget that we'll be able to reuse anywhere 79

we wish. 80

So here's a challenge. 81

So we're going to create a custom icon content widget. And as a challenge, I want you to try and extract 82

everything that is inside our cardC,hild which is going to be repeated across two cards, into a separate 83

widget. 84

So try and remind yourself how we did it for the reusableCard and pause the video and try to complete 85

this challenge. 86

All right. 87

So in order to do this, we're going to select the highest level of the widget that we want to extract. 88

So we know we have a column with some children but it's the column that we actually want to take out 89

of the main tree and create a separate widget. As long as our cursor is selected on it, 90

then we can head over to our Flutter outline and you can see here in the main widget tree, we've got 91

the corresponding column selected as well. 92

And now all we need to do is right click on it and click on extract widget. 93

And now we get to give it a name and we can call that iconContent and we're going to refactor this 94

into a separate widget. 95

Now as I mentioned before as of the latest version of Dart, we don't need the new keyword, but we now have 96

a icon content widget. 97

And it's now extracted down into here. 98

So now the next challenge for you is we've extracted this widget but we need to be able to reuse it 99

in two places. 100

So one we've already got which is here in the iconContent, but the second place is over here in the 101

second card. Because the icon content describes a column that has a icon and a bit of text. 102

But of course the icon and text are actually different between these two cards. 103

So we need to be able to reuse that icon content widget to be able to display each of these 104

no matter what icon they have. That means you're going to have to change a little bit of code that we 105

currently have in our icon content widget. 106

The end goal is to be able to have that same icon content widget to be able to create both the male 107

icon card and the female icon card by using that custom widget that we created just now. 108

So pause the video and try to complete this challenge. So in order to achieve this we're going to do 109

exactly the same thing that we did in our custom reusableCard, 110

that is create properties to be able to use in the widget that we build. 111

So over here we're going to first remove the default constructor that came when we use that extract 112

functionality that Flutter has where we extracted our icon content, and instead we're going to create our 113

own custom constructors so that we can pass over a value for the icon and also a custom value for the 114

text. 115

So first of all, let's create our properties. 116

So again it's going to have the final keyword and we're going to see that whenever we create properties 117

for our widgets. 118

And then we're going to have a data type, 119

so in this case it's going to be icon data. 120

Now how do I know that it's going to be of icon data data type? 121

Well you can always check the icon widget and you can see that for the property called icon, 122

it's expecting a icon data type. 123

So we've got our icon data 124

and we're simply going to call it icon. 125

And now we can add our second property which is going to be a string. 126

And this is going to be the label that we're going to pass over which is going to go right here so that 127

we'll be able to pass over a female when we're creating the female card, and male 128

when we're creating the male card. 129

So now we're getting some errors because we have yet to initialize these final properties. 130

Remember that final variables can only have one value and that is at the point where they are created. 131

So when this icon content gets created, the part that gets triggered is of course our constructor. 132

So I'm going to create the constructor now. And the constructor is going to have some named properties 133

and it's going to have a 134

this.icon and also a this.label. 135

Now we could make it so that both of these are required but you can also just leave it as it is. 136

So now that we've created our constructor, we've created our properties, 137

It's time to actually specify where these properties are going to go in our main build method. 138

So the first thing that's going to be custom is of course our icon. 139

So it's no longer going to be hard coded as the mars icon. 140

And we're going to change also the text to the label property. 141

So whatever is passed in through this property is going to go right here. 142

That's going to be male and female. 143

And so now when we go into our BMI calculator, the main widget tree, we can update our icon content to include 144

a icon which is going to be a font 145

AwesomeIcon.mars. 146

And then there's also going to be a label which is simply going to be the word 'MALE'. 147

And that's why this expects a string. 148

So let's hit save and now let's go ahead and also do the same for our second card here. 149

So our second reusableCard is also going to have a cardChild, and the child is going to be a widget 150

that's our icon content widget. 151

And it's also going to have an icon 152

but this time, the icon is going to be the venus symbol, venus for women and the label is going to read 153

female. Cool. 154

So now if we hit save and we head over to our app, then you'll see that we have both cards being created 155

and all of the styling is coming from our IconContent. 156

So the size of the icon, the size of the gap between the icon and the text, all of that we didn't have 157

to create again. 158

Instead we're relying on our custom widget IconContent here. And we're just passing in some different 159

values for the parts which need to change, such as the actual icon and the actual label. 160

So you can see that we're kind of starting to create our own widgets rather than just relying on the 161

out-of-the-box Flutter widget. And we're able to use these properties and our constructor to be able 162

to specify some custom content for each of the widgets that we create. 163

At this point, you can see our custom widgets are starting to take up a lot of space in our main input_ 164

page.dart file. 165

Now in this case it's actually probably quite a good idea to separate out our IconContent and our reusable 166

Card in two separate Dart files. 167

And this is because we might want to use this in other files as well, maybe in other pages or screens 168

in our app. 169

So it doesn't make sense to have it all crammed into one file. 170

So let's go ahead into our lib and create a new Dart file. And the first one I'm going to call icon 171

_content and then we're just going to click yes to add it to Git. And I'm going to also create 172

a new Dart file that's going to hold our reusableCard, reusable_card and it will create our 173

Dart file as well. 174

So now let's go ahead and take everything that's related to our IconContent and cut it out of the input_ 175

page.dart file and instead paste it in here. 176

And of course whenever we're using our material widgets, we always have to import the material package. 177

And we're also going to transplant our reusableCard over to our reusable_car.dart but not before 178

we import our material.dart package. 179

And now we can paste in our reusableCard. 180

Now if we take a look at our IconContent, you can see that we have a lot of things are pretty much hardcoded 181

right? Like the size of the icon or the size of the gap between the icon and the text or things such 182

as the style of the text. 183

Now it often makes sense to simply just take these parts out and create it as a constant at the top of 184

the file. 185

And this way if we think that we want to change the labelTextStyle, then we have to see it right at the 186

top here and we can update and edit it as we need to. 187

And inside here, we simply refer to labelTextStyle. And that way if we have lots of labels or needing that 188

particular style, then they can all refer to this constant. 189

So the final thing to fix in here is that we have a lot of errors because it no longer knows what reusable 190

Card is or what IconContent is because those widgets were removed from this file. 191

So in order to tell our file about those other widgets, we have to import the files that we just created. 192

So icon_content.dart and also reusable_card.dart 193

So now everything should be re-factored into separate files and it'll be much easier to work on each 194

of these components separately if we need to. 195

So just as the native Flutter widget will have their own file, 196

so for example if we hold down COMMAND or CONTROL on Windows and click on our text, and you can see we've 197

got our text.dart file which contains all the code for a text widget. 198

Similarly we have our own custom widgets in their own files. So we can reuse it across our project. 199

All right. 200

So if you find the import getting a bit too much and taking up too much space, it's not a bad idea to 201

simply just collapse it. 202

We never really need to refer to the imports when we're creating our code. And now our main input page 203

has a widget tree that is mostly full of layout and you can more easily see at a glance what it does 204

rather than having the tree completely exploded inside here and a million lines long, 205

we have something that's quite succinct and it's quite easy to figure out what's going on at a glance. 206

In the next lesson, 207

we're going to try and change the color of our card when we click on it, because at the moment nothing 208

really happens. 209

It doesn't seem like as if I could select either of these. 210

So we're going to solve that problem in the next lesson. 211

So for all of that and more, I'll see you there.