How to Multitask on Your iPhone 4
iPhone's iOS 4 adds a bevy of important features, of which the long-overdue multitasking feature is arguably the most significant. Multitasking works only on the iPhone 3GS and iPhone 4 models, and presumably any future models. Older iPhones don't have the resources to handle the feature.
Multitasking on your iPhone 4 simply lets you run multiple apps in the background simultaneously or easily switch from one app to another. Previously, Apple did let you multitask by, for example, playing audio in the background with its iTunes app. But multitasking was limited to Apple's own apps, not those produced by outside developers.
Here are some of the things that the iPhone's multitasking capabilities let you do:
Music from a third-party music app, like Slacker, can play in the background while you surf the Web, peek at pictures, or check e-mail. Before multitasking hit the iPhone, Slacker would shut itself down the moment you started performing tasks in another app.
If you use an Internet voice-calling app such as Skype, you can receive notification of an incoming call even if you haven't launched the Skype app.
Let a navigation app that employs GPS update your position while you're listening to an Internet radio app such as Pandora. From time to time, the navigation app will pipe in with turn-by-turn directions, lowering the volume of the music so you can hear the instructions.
If you're uploading images to a photo Web site and the process is taking longer than you want, you can switch to another app, confident that the images will continue to upload behind the scenes.
You can leave voice notes in the Evernote app while checking out a Web page.
Multitasking on the iPhone doesn't work quite the same way as multitasking on a PC or a Mac. You can't display more than one window on the screen at a time — given the size of the iPhone screen, you'd have trouble viewing multiple windows anyway.
Multitasking couldn't be easier:
Double-press the Home button.
A tray appears at the bottom of the screen. The tray holds icons for the most recently used apps.
If necessary, scroll to the right to see more apps.
Tap the app you want to switch to.
Apple insists that multitasking will not drain the iPhone battery or exhaust system resources. The iPhone conserves power and resources by putting apps in a state of suspended animation. But you can wake them up instantly and return to what you were doing.
To remove an app from the tray holding icons of the most recently used apps — and thus remove the app from those in the multitasking rotation — press and hold your finger against any app until they all start to wiggle. Then tap the red circle with the white line that appears inside the app you want to remove. Poof, it's gone.