Hi everyone, it's great to see you again
Last time we successfully used a Tab Bar Controller to manage our five main view controllers.
By the end of the last lecture, we're able to navigate the main views via the tab bar items of the tab bar controller.
We also learned to customize the UI View Controller by changing the background color of its view property.
But if you notice, the tab bar items don't look great now with the default blue color.
Let's now discuss how to customize them further.
For example, let's change them to a black color as in our design.
Also, for a better UX, it's probably a good idea to hide the tab bar item titles...
if the tab bar icons are informative enough.
OK GOOD!...
Let's change their colors.
Alright! So one of the simplest way to do this is to do it in the App Delegate,...
where people typical perform some global on-startup configurations.
Precisely, these on-startup configurations are typically put inside the application-Did-Finish-Launching method,...
which is called first when the app runs.
Of course, as this is a kind of central location, we should avoid put too much task or function specific stuff in here.
However, in our case, it's ok to set all tab bar item to the same color at once at the beginning.
Alright, this comment line tells us exactly what we can do here.
So let's do some initial customization here, like...
change the color of the tab bar items.
Our tab bar is in fact an instance of the UI-Tab-Bar class.
So let's pull our the UI-Tab-Bar class.
The idea is to customize the appearance of all instances of this class at once,...
using the appearance() method.
This will in turn be applied to our UI Tab Bar instance.
To change the color of the items, simply search for color,...
we'll quickly settle down with the tint-Color property.
Any UI Color we set to this property will be applied to the tab bar items.
As it's of type UI Color, we need to use a UI color object.
We can simply use the pre-defined black UI Color.
GOOD! Let's run the app and see.
OK, here it is.
Let's hit the sign in button the switch view.
Great! The tab bar items now have a black color.
Btw, let's delete all background color stuff,...
and some default stuff in the view controllers.
We don't need them now.
Delete these in the Discovery View Controller...
the Camera View Controller,...
the Activity view controller,...
and the Profile View Controller.
Alright, let's see how things look now.
OK, looks pretty good, right?
Now let's see what we need to do next.
OK, let's go back to our design.
You can see that each of the view should have something like a navigation bar.
This is where we can display title of a view,...
and switch views back and forth.
Like if we are somehow able to switch from the Home view to the Comments view,...
we'll able to switch back to the Home view from the Comments view, and things like that.
OK, to do so, we need something called Navigation Controller in the storyboard.
And we need to put our current UI View Controllers into a Navigation Controller to eventually obtain what we layout in the design.
So search for a Navigation Controller in the Object Library and drag it into the storyboard.
Let's see how it works.
OK, this is a Navigation Controller,...
which manages a stack of other view controllers.
Then this view controllers managed by the navigation controllers will have a navigation bar at the top.
Alright, let's put our UI View Controllers in some Navigation Controllers and see how things work.
A simple way is to directly embed our UI View Controller into a Navigation Controller.
In particular, choose this Home View Controller,...
then choose Embed In Navigation Controller in the Editor menu.
Our Home View Controller is now managed by a Navigation Controller.
It now has this Navigation bar or item at the top.
Another way of doing this is as follows.
Let's delete the connection between this Navigation Controller and the View Controller it manages.
Now these two are separate controllers.
Select the Navigation Controller, Control drag to the other view controller,...
then choose root view controller segue,...
then this view controller will be come the root of the stack of view controllers that the Navigation Controller manages.
Alright, let's delete these two; we used them for demonstration only.
Now let's see we can do with the navigation item.
We can set a title in its Attribute Inspector, let's say Home.
Alright, let's check it out.
Alright, let's see.
GREAT! This UI view controller now has a Home navigation bar.
We now need to do this thing to the other UI view controller.
Very similar, simply add embed this into a Navigation Controller.
This Camera View Controller too,...
the Activity View Controller,...
and finally, the Profile View Controller.
A valuable thing we have when using Navigation Controllers is that it can manage a stack of many UI View Controllers.
We'll talk about that later.
For now, let's just set titles for the new navigation bar.
This navigation item should have a title, say...
Discover.
The next one, probably...
Camera.
And the fourth one,...
Activity.
Finally, the last one,...
Profile.
GOOD! Let's check them out.
Alright, let's see...
FANTASTIC, looks pretty good, huh?
Now, the text down here looks kind of annoying.
Let's get rid of them. The icons are informative enough.
Moreover, we now have sort of a title for each view.
To delete them, choose the corresponding tab bar item,...
then delete the title of the bar item.
Let's run the app and see how it looks now.
GREAT! Things look much cleaner now.
However, there's a problem, this icon is a bit off.
This is because there's some default space for the bar item title.
We now need to push this icon down a little bit.
Let's choose the Home tab bar item.
In its Size Inspector,...
we'll see the Image Inset attribute.
We use this attribute to position the icon in the corresponding tab bar item.
It's current zero away from the top, let's use something like 5 to push it down a bit.
OK, it's a bit further away from the top, but the system scaled the icon to obtain that effect.
The trick to fix this is to push to bottom down the same amount to compensate the top.
So the amount we need to push down the bottom should be the same as what we did to the top,...
but the sign should be different.
If we use 5, that means we push the bottom up, not down.
So actually we need to use minus five.
That would bring the image back to its normal shape.
Great! You can see that our icon is back in its normal shape, and is pushed down a little bit to make things look balanced.
We don't need to adjust left and right sides, 'cause it's centered already.
Let's check this out.
You can play around with a few settings to move the icon to whatever position that you like.
Alright, let's switch view.
FANTASTIC!
It looks much more balanced now.
OK, let's do this to the other tab bar items.
For the search bar item,...
Push the icon down the same amount as we used for the Home bar item.
In its Attribute Inspector, delete its title.
Similar for the Camera bar item.
Delete the title,...
and push the icon down.
OK, let's delete the title again.
Now the Activity bar item,...
delete its title,...
and push the Heart icon.
And finally the Profile bar item.
Push the icon,...
then delete its title.
GOOD! Now let's run the app to check things out.
FANTASTIC!
We'll learn storyboard references next time! See you then!
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