TAILIEUCHUNG - Ebook Beginning android 2: Part 2
(BQ) Part 2 book "Beginning android 2" has contents: Handling rotation, working with resources, using preferences, accessing files, leveraging java libraries, communicating via the internet, creating a service, alerting users via notifications,. and other contents. | 185 19 Chapter Handling Rotation Some Android handsets, like the T-Mobile G1, offer a slide-out keyboard that triggers rotating the screen from portrait to landscape orientation. Other handsets might use accelerometers to determine screen rotation, as the iPhone does. As a result, it is reasonable to assume that switching from portrait to landscape orientation and back again may be something your users will want to do. As you’ll learn in this chapter, Android has a number of ways for you to handle screen rotation, so your application can properly handle either orientation. But realize that these facilities just help you detect and manage the rotation process. You are still required to make sure you have layouts that look decent in each orientation. A Philosophy of Destruction By default, when there is a change in the phone configuration that might affect resource selection, Android will destroy and re-create any running or paused activities the next time they are to be viewed. While this could happen for a variety of different configuration changes (., change of language selection), it is most likely to trip you up for rotations, since a change in orientation can cause you to load a different set of resources (., layouts). The key here is that this is the default behavior. It may even be the behavior that is best for one or more of your activities. You do have some control over the matter, though, and can tailor how your activities respond to orientation changes or similar configuration switches. It’s All the Same, Just Different Since, by default, Android destroys and re-creates your activity on a rotation, you may only need to hook into the same onSaveInstanceState() that you would if your activity were destroyed for any other reason (., low memory). Implement that method in your activity and fill in the supplied Bundle with enough information to get you back to your current state. Then, in onCreate() (or onRestoreInstanceState(), if you prefer), .
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