I've read several post regarding singleton class destruction or singleton pattern is bad in android like this and this
But I am not able to understand how to declare a singleton class properly or use sharedpreference for persistance can anyone provide any example on how to maintain global objects across application or how to achieve this in proper way any help is appreciated.
I think this link you mentioned is quite good.As my personal experience the best way to maintain global objects in an application is to use a class that extends from Application class, then you can manage objects by setter and getter methods in that class.This technically works like a Singleton in android except most of house keeping is done by android so it's very wise to use this mechanism instead of singleton.
On the other hand shared preferences has entirely different job and used for mainly storing some user data and behavior
To save data between process termination you have to use serialization in any form.
The easiest way is to use sharedpreferences + gson.
Singleton would not help because all data with the process will be wiped, OS have a handler to save state in "low memory" situations but it still uses serialization (bundles).
You may use singleton with sharedpreferences, data clients (activities) have to notify about destruction, so singleton can dump data. At start singleton will load data again.
But be aware of possible inconstancy - what if an app will crash?
Things get trickier with multiple processes in one application.
