Re-thinking App Switching on the iPhone
When thinking of the term 'multitasking' in a mobile context, we inherently think of compromise. While this is partly due to nitty gritty specifics such as a device's exact screen real-estate or tech specs, an underlying reason the thoughts of compromise persist is due to our personal experience; clumsy and slow. So what is the real inhibitor? With a lack of speed, the 'tech specs' answer may naturally come to mind again. However, this (especially today) can no longer be pointed to as the core excuse of a crippled multitasking experience on mobile. So what might it attributed to? In a word:
Though versatile, multi-touch (especially in a mobile setting) can rarely—if ever—rival the levels of efficiency that the keyboard, mouse, or trackpad combinations provide. That said, anyone who's used an iPhone for the first time can tell you that there are some experiences where multi-touch alone shines through.
What Works and What Doesn't
On your iPhone, the ideal multitasking experience is to be able to quickly jump from the app you're in, to the app you want to be in, with as few steps as possible. Think 'cmd+tab' levels of productivity, for mobile. The following are some pillars of what make up this app switching experience.
What we also want from an app switcher (whether we're aware of it or not) is for it not to feel like an extra presence of the OS; a barrier. One of the under-appreciated aspects of iOS's native app switching is what happens to the screen you were previously viewing, when calling upon the switcher; The screen simply slides up. Along with establishing familiarity, keeping the previous window in view (taking up most of the screen, in fact) lets the user know how instantly they can jump right back into what they were doing. They haven't exited into an "app switching mode".
As many can attest to, relying on a double click of the home button is hardly the most convenient or pleasurable way of accessing anything, be it the app switcher or the lock screen's music controls. Partly due to the reliability of the input itself, but another reason is how it detracts the use of touch to get from one place to another; A chore. Imagine if you had to double click the sleep/wake button in order to display notification center, for example. Use of physical inputs on a touch driven device intrinsically adds a barrier to the experience. This is why they work best with 'instant end goal' actions such as locking the device, exiting an app, increasing volume etc, where there are no following inputs to be expected from the user.
Although the 'screen real-estate' excuse may be valid when discussing compromise within mobile multitasking, it isn't one that can't be overcome. There's a reason why desktop users wish to see the state of their windows even before switching to them; it provides a sense of 'instant access'. Similarly to the way iOS's switcher subtly retains the thing you were just viewing (despite being in-actionable), showing the state of an application without giving it primary focus blurs the line between using an app, and switching to it. It's informative, but also welcoming. Thus the issue with displaying 'previews' is not with their importance or feasibility, but with their worth at the cost of speed and number of inputs to use.
By far the most pivotal in relation to the feeling of 'speed', is the amount of inputs the user has to go through to get from point A to B. The more steps you exert on the user, the more likely they are to associate that task with being a chore, even if it's 'only' a few clicks, taps, or swipes. Just like desktop's 'cmd+tab' function offers instantaneous reward, so should mobile multitasking methods, if possible. The multi-touch equivalent can be found in everything from slide to unlock to accessing notification center; Single-input. Much can happen in a single touch, slide, and release.
To put it simply: Maximizing speed by minimizing inputs, allowing maximum information. At the end of the day, it's about clearly being able to get from one place to another. Doing so with efficiency means instant access, with productivity being adequately informed. The less compromise in these facets, the better the experience.
This is an example of what an optimum app switching experience could look like:
While brief, it gives you an idea of how speedy an app switcher can be while simultaneously displaying much more information.