android-lifecycle

I would like to know, why OnCreate() is called only once at the start of an activity? Can we call OnCreate() more than once in the same activity? If yes, than how can we call it? can anyone give an example? Thanks a lot!!! Why would you want to called it again? unless the activity is reconstructed, which is called by system. You cannot call OnCreate manually , it is the same reason why you won't call setContentView() twice. as docs: onCreate(Bundle) is where you initialize your activity. Most importantly, here you will usually call setContentView(int) with a layout resource defining your UI,

I'd like to save the state of my application so that when it is reopened from a closed state, the last fragment is visible and the back stack is preserved. I'd like to preserve this state every time the application is closed, not just on an orientation change or when the system kills the app to free up resources (as is the case when using onSaveInstanceState() / onRestoreInstanceState() . So far I've been able to restore the previous fragment and its state as planned by saving the state to SharedPreferences and restoring it later. However, this does not preserve the fragment back stack, so

I am working on animating custom Views for my Android app. I have accomplished this via Property Animations and calling invalidate() on the View in the onAnimationUpdate() callback, as per https://developer.android.com/guide/topics/graphics/prop-animation.html : Depending on what property or object you are animating, you might need to call the invalidate() method on a View to force the screen to redraw itself with the updated animated values. You do this in the onAnimationUpdate() callback. My problem is that when these animations are run at the beginning of a newly launched Activity, they

I have a problem with Activity navigation and the back stack and I was hoping you could clear it up for me. The Problem Root Activity >>> SecondActivity >> HomeButton This then takes me to the home page and from there I select... Gmail >> Message >> Open attachment in my application >> ImportActivity >> RootActivity The outcome is a new task being started and another instance of my application being used. This is unacceptable as I don't want two separate tasks running I only want one. The Desired Outcome What I want to happen is when the user opens the attachment and ImportActivity finishes

I'm trying to find the official documentation about the Android Application class lifecycle. Apparently, for what I found on StackOverflow here and here the Application class can be killed if the system needs memory. Even this tutorial says so. But few things irritates me a bit about this: I can't find an official documentation telling me that yes, the Application class can be killed on low memory. I can't find any official diagram representing the Application lifecycle neither. I can't find any proper callback to use when the Application class is killed except onLowMemory() . Does it mean

I've read several posts that describe the difference between onStart() and onResume() : onStart() is called when the activity becomes visible, onResume() is called when the activity is ready for interaction from the user. fine. I've always just added code to onPause() and onResume() , and never bothered with onStart() and onStop() . Can anyone give some concrete examples of what you might do in onStart() , vs. onResume() ? Same goes for onStop() and onPause() , how is onStop() useful? I must be missing something fundamental here. onStop() will (for example) be called when you leave the