What's responsive?

Tags
Fill in the blank

Columns in Bootstrap grids

How many columns are in Bootstrap's grid?

Your answer:
Saving
Not graded. So why do it?
Fill in the blank

How many columns for the content area?

Here's part of a BS grid layout.

  • <div class="row">
  •   <! - Sidebar - >
  •   <div class="col-3">
  •     <p>Sidebar stuff</p>
  •   </div>
  •   <! - Content - >
  •   <div class="col-??">
  •     <p>Content stuff</p>
  •   </div>
  • </div>

What should probably be where the ?? is?

Your answer:
Saving
Not graded. So why do it?

Lesson contents

Making pages responsive is more complex than anything we've done before. You can learn it, but we have to take it slowly.

This lesson is about the basic principles of BS's responsive grid system. We won't be doing realistic tasks in this lesson, just tasks that show the responsive grid system in action.

In the next lesson, we'll use the principles you learn here on real layouts.

The problem

You want your site that looks good on a desktop, and on mobile devices, like tablets and phones. You have two choices:

  • Make two different sites.
  • Make one site that adjusts to screen size.

The smart money is usually on the second one. It's cheaper to create and maintain one site than two.

BS helps you make responsive sites, that is, sites that adapt to different screen sizes. This lesson is about how you do that.

Your browser can mimic devices

Desktop browsers can mimic mobile devices, so you can see what your site looks like on smaller screens. Here's the toggle-device-toolbar button Chrome's dev tools:

Toggle device toolbar button

The toolbar shows at the top.

Toolbar

Use the left dropdown to choose a device. For example:

Choosing a device

Then you can see what the page looks like on that device:

The page on a Galaxy S5

Ray
Ray

That's so cool!

Isn't it?

You can change the zoom factor as well:

Changing the zoom

Now let's see what would happen if you rotate the phone. There's a button for that:

Rotate

Here's what it looks like in landscape:

Page in landscape on a Galaxy S5

Georgina
Georgina

That list of phones you had.

This one?

Choosing a device

Georgina
Georgina

What if you want to use a phone that's not on that list?

No problem. There's an edit button at the end of that list. Click, and see a long list of devices you can choose:

Device list

Marcus
Marcus

Wow! Blackberries, and Windows phones.

Right. And tablets, laptops, you name it. You can add other devices, if you want, too. Like, I dunno, a browser on a t-shirt.

Adela
Adela

Does that really exist?

Not as far as I know, but it's only a matter of time.

Exercise

Exercise

Page on an iPad

Make a screen shot, showing what this sample page would look like on an iPad.

Include something showing what device your browser is simulating, like Chrome's device toolbar. For example, here's a screen shot showing the device being simulated.

Screen shot

(Your screen shot will be of a different page, on a different device.)

Use whatever zoom you want, but 40% is good.

Hint: it's easy with Chrome.

Upload the screen shot.

The BS device breakpoints

OK, so how does BS let you make a site that adjusts to screen sizes?

First, you need to know about breakpoints. In CSS, there are things called media queries, that let you apply different style rules to different screen sizes. For example, this code sets page background color, depending on screen size (or browser window size):

  • /* Set base background color */
  • body {
  •   background-color: white;
  • }
  •  
  • /* For screens that are 900px or less, set the color to antiquewhite */
  • @media screen and (max-width: 900px) {
  •   body {
  •     background-color: antiquewhite;
  •   }
  • }
  •  
  • /* For screens that are 500px or less, set the color to lightyellow */
  • @media screen and (max-width: 500px) {
  •   body {
  •     background-color: lightyellow;
  •   }
  • }

You can try it. Resize the browser window, and watch what happens.

This example doesn't use Bootstrap, just media queries created manually. You won't be writing media queries yourself. You'll take advantage of media queries that are already in BS's stylesheet.

Five BS screen sizes

Here's one of those media queries again:

  • @media screen and (max-width: 900px) {
  •   body {
  •     background-color: antiquewhite;
  •   }
  • }

That 900px is a breakpoint. BS sets some sensible breakpoints in its stylesheet, that work well with different kinds of devices. Here they are.

Name Size Class prefix
Extra small < 576px col-
Small >=576 px col-sm-
Medium >=768 px col-md-
Large >=992 px col-lg-
Extra large >=1200 px col-xl-

(">=" means "greater than or equal to.")

We'll get to the class prefixes later.

When you're working with BS, you don't worry about exact display sizes. You work with small, medium, etc. Leave BS to worry about the deets.

On a phone, a web browser usually takes up the whole screen. So, the screen size and the browser window size are the same.

On a desktop PC, you might have several windows open, with a browser taking just part of the screen. The browser window size is smaller than the screen size.

The breakpoints are really talking about browser window size, not screen size. So, make a browser window small on a desktop, and the browser will show you what the web site looks like on a screen of that size.

But how do you get different layouts on different displays? Let's check out some examples.

Two-column page

Say we want a page that has two side-by-side columns on most screens:

Columns side-by-side

But on an extra small screen, like a phone, we the columns to stack up, like this:

Columns in a stack

Remember, this is the same page. We want to write one HMTL file, that adapts itself to browser window size. Making one file is cheaper and easier than making two.

You can try this example. Make the browser window smaller and larger, and watch the magic.

Here's the code for that page, just the body:

  • <body>
  •   <div class="container">
  •      <div class="row">
  •         <div class="col-xs-12 col-sm-6 border h4"><strong>Column 1</strong></div>
  •         <div class="col-xs-12 col-sm-6 border h4"><em>Column 2</em></div>
  •      </div>
  •   </div>
  • </body>

The border and h4 class just make the text and columns easier to see. Let's get rid of them and some other things, so we can focus on the important stuff:

  • <div class="col-xs-12 col-sm-6">Column 1</div>
  • <div class="col-xs-12 col-sm-6">Column 2</div>

Remember that there are 12 grid columns in BS.

12 column grid

No matter how big the browser window, there are always 12 columns. On a smaller window, the columns are narrow, maybe 80px on a wider screen, and 40px on a narrower one.

Now, when the window is extra small (less than 576px), the browser applies classes starting with col-xs-, if you've typed them in your HTML, and ignores other col- classes.

When the window is small (more than 576px but less than 768px), the browser applies classes starting with col-sm-, and ignores the other col- classes.

Here's that window size table again.

Name Size Class prefix
Extra small < 576px col-xs-
Small >=576 px col-sm-
Medium >=768 px col-md-
Large >=992 px col-lg-
Extra large >=1200 px col-xl-

The class prefix is what you use in class names for divs.

So, for...

  • <div class="col-xs-12 col-sm-6">Column 1</div>
  • <div class="col-xs-12 col-sm-6">Column 2</div>

... when the window is extra small, the browser uses col-xs-12 for both divs. When the window is in the small range, the browser uses col-sm-6 for both divs.

There are 12 grid columns, so when each div has six of them, that's half the container width for each one. So the divs end up side-by-side:

Columns side-by-side

When the window is in the extra small range, the browser uses col-xs-12 for both divs. That's the entire container width for each one.

The divs are in the same row:

  • <div class="row">
  •   <div class="col-xs-12 col-sm-6">Column 1</div>
  •   <div class="col-xs-12 col-sm-6">Column 2</div>
  • </div>

When one row has more than 12 grid columns, BS wraps them onto the next line. That's what makes this whole responsive thing work. The first div takes 12 grid columns (the entire container width). The browser runs out of space, so it goes to the next line. The second grid then takes 12 columns.

We get:

Columns in a stack

That's what we want. Columns either side by side, or, on extra small screens, stacked.

You should try it. Change the window size, and see what happens. Check out what the page looks like on different devices.

Larger windows

Here's the code again.

  • <div class="row">
  •   <div class="col-xs-12 col-sm-6">Column 1</div>
  •   <div class="col-xs-12 col-sm-6">Column 2</div>
  • </div>

It has classes for extra small, and small windows. What about larger windows?

When the window is larger than any of those given in the list of classes (like medium, large, or extra large), the browser uses the largest one that has been given.

Ray
Ray

Huh? I don't get it.

Both of these divs...

  • <div class="col-xs-12 col-sm-6">Column 1</div>
  • <div class="col-xs-12 col-sm-6">Column 2</div>

... have classes for extra small and small windows. If the window is in the medium range, the browser will use the biggest class it's given, that is, the small class. If the window is extra large, the browser will use the biggest class it's given, that is, the small class.

Suppose we change it to this...

  • <div class="col-xs-12 col-sm-6 col-md-3">Column 1</div>
  • <div class="col-xs-12 col-sm-6 col-md-3">Column 2</div>

On an extra small window, each div would have 12 grid columns. On a small window, each div would have six columns. On a medium window or larger, each div would have three columns.

Exercise

Exercise

Four dogs

Make one HTML page showing four dog photos. How they're arranged depends on the window size. For large and extra large, all four are on one row.

Four dogs per row

For a small or medium window, there are two dogs per row.

Two dogs per row

For an extra small window, there is one dog per row.

One dog per row

You can use these photos:

Doggo Doggo Doggo Doggo

Use at most three col_ classes for each column, like this:

  • <div class="col-?? col-?? col-??">

This might be useful:

  • <img class="m-1 p-1 border" src="dog1.jpg" alt="Doggo">

Submit your URL, as usual.

Up next

You've learned the principles of the responsive grid system, but how do you use it for real sites, like your final project? That's up next.