mobile and app development

Welcome to Getting Started with Mobile Web Development. A short crash course where you’ll get to set up and build responsive, multi-device web apps and sites using Chrome developer tools. MALE SPEAKER: And one of the first challenges with developing for the mobile web is the display screen. The typically small display screen, compared to a desktop or a laptop device, really forces you to focus on what’s critical for your users. In today’s landscape, you should really think of your designs in terms of three main scenarios, phone, tablet, and desktop.


These may share some design characteristics of course, and they’ll certainly share data, but you should consider the optimal experience for each of these scenarios separately as you build your design. MALE SPEAKER: As you can see, Chrome Dev Tools provides a series of tabs that allow you to debug and inspect your web apps. For example, you can select any element on the page by right-clicking the element and selecting Inspect Element. Or, as I’ll do here, you can click on the magnifying glass and hover over an area that you would like to inspect. The set up is simple. All you need as an Android device, a USB cable, and your development machine.

ios app

Let’s take a look. Before you get started, you need to turn on the Developer Mode in your Android device. This may be different on any given device. And you can check your device manual for how to do this. In many cases though, you need to go to your device’s Settings, click on AboutDevice, and then click on Build Number seven times. Seriously. Next, you’ll want to turn on USB debugging.


Again, this varies slightly on your given device but is usually located in the Developer Options. We also need to make sure we have the right tools installed. On my laptop, I have Chrome Canary. And on my mobile device, I have Chrome Beta installed. Now that we have everything set up the way we need, open Chrome on your development machine, and go to Chrome Inspect. Make sure the site you want to debug is open on your mobile device, and then connect your laptop to your mobile device via USB.

development machine

Then confirm that you want to allow USB debugging. Back on our development machine, we can see a list of the attached devices and the Chrome tabs that are open on the device. You can even open other tabs. You can also focus on specific tabs. MALE SPEAKER: When mobile browsers first came along the content on the web wasn’t designed for narrow, small screen devices.


It was designed for windows that were around 1,000 pixels wide, and wider than they were tall, with easy scrolling. To shoehorn this content into a tiny, mobile screen, since rendering a web page designed for 1,000 pixels across a 320-pixel wide screen would mean you’d scrolling a lot, mobile browsers basically lied about the window width. They made the window act as if it was 980 pixels wide, even though the original iPhone was only 320 pixels across.

This enabled sites that were designed for 1024 by 768 screen, that is, that were around 980 pixels wide, to fit on the mobile screen. Although you needed to do a lot of zooming to read the text sometimes. Unfortunately, if your site did not happen to match that980 pixel width, you were either going to overflow or underflow the screen. Either wasting space, forcing the user to zoom. In order to control this, Apple-provided a viewport meta tag to be added to your HTML to control the default for how big should my screencast on this page. The default is 980. So if you put 980 here, it would have no effect.

The mobile browser already defaults to 980. But setting a viewport tells the browser how wide the content is intended to be, and then the browser scales to make that size fit on the device’s screen. There are two ways to use this tag. Although typically viewport is only being set on load, you can actually play around with the viewport settings in the development tools to tweak it and get it just right.

If I go into the page and set the viewport meta element contents from the Mobile Dev Tools, it will change the page as if it had been refreshed. However, and this is where it gets a bit confusing, the zoom level is maintained by the browser across page refreshes.

So when you change viewport settings in the source code, and you’re reloading, be sure to actually close the tab first. Don’t just hit reload, or it won’t necessarily show the effects on the screen. So let’s try this out on this page. Let’s add a device width element to our lorem ipsum page, and refresh it on the mobile browser.

Mobile device

This is what a page looked like before. Now, with the meta tag in place, let’s try reloading it. And you can see the page now chooses a better size because it’s reflowing at the native size of the screen. MALE SPEAKER: So really, fixed viewport widths are historical. Resizing by default was an attempt to shoehorn the desktop web into a mobile device. Fixed viewport sizes were a quick way to provide some minimal controls on that resizing. With Device, Width gets us back to the same scalable sized canvas that the desktop web has. So the right way to do fluid, flexible design in the modern mobile web starts with this tag. This marker lets the browser know you’re one of the cool kids, and you know what you’re doing. There is one more thing on viewports.

You’re naturally going to want to layout elements on the page relative to the size of the viewport. Particularly, when you’ resizing columns on the page, for example. So we have a new unit type in CSS called viewport units. You can use these units to size things in the percentage of the width of viewport percentage of the height of viewport without having to push percentage sizing everywhere, which makes things a little easier. The really exciting thing is this unit types even work in desktop browsers, as well as in mobile browsers. MALE SPEAKER: So now that you know how to set the viewport meta, let’s poke around in the developer tools to see what we need to do to fix this page. Now the biggest problem here is that the page has a fixed column width.

If I resize the window, you’ll notice the column of text doesn’t actually change the size, just margin position. As we mouse around the elements inside the DevTools, we can pretty quickly find the first offending element. This page element here actually has a width set on it. Let’s disable that and see what happens. Well, it certainly changed things, but I don’t think it actually improved things very much.

Let’s keep digging inside the content and see what we can find. This wrapper element has a width of 100% already, which is good. It means that it’s not preventing us from resizing. But this content element does have a width set in pixels. Let’s disable that. Now as we resize the page our content is fine, but the sidebar is appearing and disappearing. Sure enough, it has a width set.

So now let’s go back up to the page, and let’s try giving it a width. But let’s give it a width viewport unit instead. Now our only remaining problem seems to be that the header is actually not resizing as we want it to. Let’s go take a look at the header image again. The image has a max-width set, but not just width. So let’s set its width. And now everything seems to be resizing well. Now, this isn’t perfect.

Be sure to create fluid layouts. Be sure to reflow to use all the space on the screen, and take advantage of every bit you can. And be sure you adapt to different screens as well. One tool that makes reflow lot easier, particularly across very different screen sizes, is the new Flexboxlayout in CSS.

This new tool lets you stack elements in flexible rows or columns. MALE SPEAKER: Responsive design isn’t just about flexible fluid designs, it’s also about adapting to different scenarios and environments. And our primary tool for doing that is Media Queries. Media queries have their roots in the media type for style sheets.

For example, it’s helpful to display the URL of hyperlinks when printing, since you can click on the links on paper. So that’s what this rule does. But CSS3 Media Queriesadded media query terms. This lets us make conditional rules in our style sheets based on environmental factors like the width of the window,

or the orientation of the device. This opens up a huge opportunity for us to make truly adaptive layouts.

MALE SPEAKER: This was a crash course in mobile web development and using Chrome Developer Tools to build responsive,multi-device web apps and sites. For more best practices and how to’s, check out the full mobile web development course, on Udacity. You could also find more information on the web fundamental site. All the best, and happy coding

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