活动生命周期？

Question

I think my ideas on activity lifecycle and bundles
are a little confused,can you help me?

Let's suppose the user opens activity A from home screen,
activity A "calls" activity B which fills the screen.
On this event onSaveInstanceState() is called on activity A then onPause() and onStop() .
Since there are too many apps currently running on the system,
andorid decides to kill the process hosting activity A .

When the user navigates back to activity A ,onCreate() is called an we can
use the bundle ( setted during the last call of onSaveInstaceStae() ) to restore the state. then onStart() , onRestoreInsanceState()
and onResume() are called,
am I right?

Then lets suppose the user presses back key to exit from activity A
onPause() , onStop() and onDestory() are called in sequence on activity A (the call of onDestroy() could be postponed though) onSaveInsanceState() should not be called in this scenario.

When the user opens again activity A later on then the bundle
passed to onCreate() is null,right?

Now Suppose the user rotates screen onSaveInsanceState() , OnPause() , OnStop() , OnDestroy() are called
then onCreate() with bundle setted by the last call to onSaveInsanceState() ,
and then onStart(), and onRestore(). am I right?

My guess is that:

when the user creates an ativity,the bundle passed to onCreate() is always null and onRestoreState() is never called,but when the system creates it , for instance when it killed the activity because of low memory or because of a rotation event,the bundle passed is the one setted by the last call of onSaveInstanceState().

Is my guess right?

thanks and sorry for my poor english.

PS : I think onRestoreInstanceState() is passed the same bundle is passed onCreate() but typically state is restored using onCreate() .

Answer 1

onRestoreInstanceState（）传递相同的bundle传递onCreate（）是正确的，并且系统通过调用onCreate（）重启活动并且还调用onRestoreInstanceState（），如果从活动开始时从onCreate（）获取，则bundle将为null 。

Answer 2

Since there are too many apps currently running on the system, andorid decides to kill the process hosting activity A.

This is a very common situation. Furthermore - you can emulate this action using developers option.

In this case each activity, that was move into background, will be automatically destroyed.

About Bundle in OnCreate .

I can get from my memory only two cases when OnCreate will be called with non-null Bundle. First - described above. Second case - screen rotation.

When you launch app Android calles

• onCreate
• onStart
• onResume

After that lets doing screen rotation. Android will call

• onSaveInstanceState
• onPause
• onStop
• onDestroy
• onCreate
• onStart
• onRestoreInstanceState
• onResume

The more information you can find on topic about recreating

Answer 3

Interesting question - never thought about it.

Take a look at the documentation, onCreate() and onSaveInstanceState() .

This answers at least your question what Bundle will be supplied to onCreate() .

Unfortunately there is no exact definition on which events onSaveInstanceState() is called, but I guess it is called by default in all relevant situations (whatever they may be...), but you can find out for some situations (eg rotating the screen) by putting a Log.i() to LogCat.