Android - activities lifecycle

lets imagine this application like enclosed image. R stands for Root activity and A and B are other activities. A is for displaying of some list, B stands for displaying detail of some value. From R I can get by 4 buttons to 4 A activities. My question is, whether in this scenario is A activity initialized for each time or I would be using only one A activity among whole application. If user selects A in right top corner activity A, then displays detail B and then from detail B goes to another list (but based on A activity). Will he still got the same content from the first A or he can have "new" A activity with another list?

Here is the point - I will be having let's say hundred of activites. Lot of them are "forms" displaying some content, application will have about 50 variants of those forms.开发者_运维问答 Can I make for each form one activity a reuse it again in my activity without having connections to past usage of this activity?

Use android:launchMode="singleInstance" in your manifest if you want a single instance of your activity class

By default activities start over entirely every time you open them with a call to startActivity(). If your activity starts a new activity, it will essentially be put on to an activity stack and is paused while the new activity starts. If the user presses the back button, the last activity on the stack will resume as it left off (though I don't think this is 100% guaranteed as Android will kill off tasks as it needs resources so I wouldn't assume it).

So if you have this chain here:

A->B->C->D

where each letter represents a new activity with absolutely no flags or changes.

If the user is at D and presses the back button, C will resume. D is popped from the stack. If the user decides to go to activity D again, a new D will start as if it didn't happen (assuming you didn't save any persistent variables). If the user presses back twice, the application will be at B where C and D are no gone.

You can manipulate this chain with various flags like singleInstance to keep its state, or noHistory to ensure it doesn't get put to the stack (meaning it will be skipped if the user presses back).

Very detailed description of the various attributes