How to save/restore global variables in android even when os kill application

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http://stackoverflow.com – In android,Google recommends us to save the global variables in Application. But there is a problem, if the android os kill the application because of low of memory, the application will be re-oncreate and the global variables I saved will be lost. I don't know when to save/restore these variables,application doesn't give us some methods such as onsaveinstancestate()/onrestoreinstancestate(). I have one idea but I can't make sure it can work well. I see some app will go to slashScreen when os killed it, maybe we can save these gloabl variables in SplashAvtivity? Because Activity has the met (HowTos)