Android: Efficient Screen Rotation Handling

问题:

In Android, when the screen orientation changes (between landscape and portrait) the onCreate method is called which ,if not handled properly, will recreate the entire activity when the result is too simply change the layout and retain all of the same information.

I know of a few ways to solve this, but I'm interested in the most efficient way.

1) Telling the manifest that I will handle the orientation change by overriding the onConfigurationChanged() method and leaving it empty.

2) override onSaveInstanceState() and save the data here to be repopulated in onCreate()

3) Override onPause() which will create a bundle of the data and send it to onSaveInstanceState()

Obviously, these are all options, but which one is a better practice (small, medium, large amounts of data)

Thank you

回答1:

Some device configurations can change during runtime (such as screen orientation, keyboard availability, and language). When such a change occurs, Android restarts the running Activity (onDestroy() is called, followed by onCreate()).

• To properly handle a restart, it is important that your activity restores its previous state through the normal Activity lifecycle, in which Android calls onSaveInstanceState() before it destroys your activity so that you can save data about the application state. You can then restore the state during onCreate() or onRestoreInstanceState().

However, you might encounter a situation in which restarting your application and restoring significant amounts of data can be costly and create a poor user experience. In such a situation, you have two other options:

1. Retain an object during a configuration change

   Allow your activity to restart when a configuration changes, but carry a stateful Object to the new instance of your activity.

2. Handle the configuration change yourself

   Prevent the system from restarting your activity during certain configuration changes, but receive a callback when the configurations do change, so that you can manually update your activity as necessary.

So, As per your data operation and coast of user experience with application you can choose what is best for you..

EDIT: As per your need for just change the layout I think you have to use onConfigurationChanged() and do the changes in it.