CODEWITHSUNDEEP
androidandroid-intentmemory
1020rpz
1020rpz

Reputation: 924

Android Intent And Memory

I'was wondering a simple thing. I'm making an android app and I started asking my self about memory usage.

What does the android OS make when I call a new intent??

Imagine i have an intent with only one button and this button onclickmethod is making a new intent of the same activity.

If on click I do this??

Intent activityN = new Intent(Activity.this,Activity.class);
startActivity(activityN);

is the firstActivity killed or does android keep it?

And if I click 50 times??

thanks for your answers

Upvotes: 1

Views: 1229

Answers (3)

ezaquarii
ezaquarii

Reputation: 1916

Activities life cycle is a tricky topic.

In most cases the activity will be kept in memory, but in some cases Android may decide to destroy it to reclaim resources. You have no control over this behaviour, which may change between OS versions and even hardware configurations. Don't try to fight it - embrace it.

Activity state is saved in onSaveInstanceState(Bundle), which is called before placing the activity in a background state.

When the Activity is about to be shown - but was destroyed to reclaim resources - it can be recreated using savedInstanceState in onCreate() method. You are expected to handle this situation. Most programmers don't care, which leads to strange errors on screen rotations and after longer periods of inactivity.

You may think about this mechanism as a serialization/deserialization scheme, that allows Android to optimize memory usage, discarding the data that can be recreated on demand (such as UI layout) and saving only things that cannot be recreated, such as UI state (entered text, checbox states, etc).

Since Activity destruction is rather unpredictable under normal conditions, Android provides special developer's option to always destroy activities when possible. This allows you to properly handle all corner cases around activity life cycle without too much effort. Explore your device's developer options.

You may want to check out those articles to learn more about the topic:

Going back to your question about clicking the button 50 times... it will probably create 50 instances of activity, stacked on top of each other. It may be the case that Android starts to destroy first activities to make room in memory for new ones. Let's say that the device have memory for only 49 activities. You start 49 - all are kept in memory. You start 50th one and the 1st is going to be destroyed. Her state is saved in Bundle, so when you press back 49 times, the first one will be re-created from this saved bundle.

Upvotes: 2

Alexander
Alexander

Reputation: 48252

That depends on the flags you are supplying with your Intent.

If no flags then every startActivity creates a new Activity.

However, there can be FLAG_ACTIVITY_CLEAR_TOP orFLAG_ACTIVITYY_SINGLE_TOP flags.

It's boring to repeat it all here, have a look at the docs:

http://developer.android.com/guide/components/tasks-and-back-stack.html

Upvotes: 2

Gabe Sechan
Gabe Sechan

Reputation: 93561

Android keeps the first Activity. That's why when the second Activity is finished you can return (with results even) to the same state. If you clicked the button 50 times, you'd start 50 new activities. YOu generally want to avoid that, so its a good idea to disable the button after the first press. Luckily your new activity should quickly start and cover up the button, so 50 is hard to do (although 2 or 3 isn't).

Upvotes: 1

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