What does finish do in android

When calling finish on an activity, the method onDestroy is executed. This method can do things like:. Also, onDestroy isn't a destructor. It doesn't actually destroy the object.

It's just a method that's called based on a certain state. Android keeps processes around in case the user wants to restart the app, this makes the startup phase faster. The process will not be doing anything and if memory needs to be reclaimed, the process will be killed.

A method group is the name for a set of methods that might be just one - i. However, when I click on the menu button of the device which shows all the app running in background I still see my activity How can I fix it? While calling your activity FirstActivity which you want to finish as soon as you move on, You can add flag while calling FirstActivity. But using this flag the activity will get finished evenif you want it not to. Whenever you wish to exit all open activities, you should press a button which loads the first Activity that runs when your application starts then clear all the other activities, then have the last remaining activity finish.

Also, onDestroy isn't a destructor. It doesn't actually destroy the object. It's just a method that's called based on a certain state. Android keeps processes around in case the user wants to restart the app, this makes the startup phase faster. The process will not be doing anything and if memory needs to be reclaimed, the process will be killed. I performed a simple test on finish method. Listed important callback methods in activity life cycle. What I mean to say is that counterparts of the methods along with any methods in between are called when finish is executed.

Also notice if you call finish after an intent you can't go back to the previous activity with the "back" button. If you don't override it, the system does what it has to. And hence, it calls up onDestroy after that. As we know, the android system is free to kill activities if it feels that there are resources needed by the current Activity that are needed to be freed. Finish method will destroy the current activity.

You can use this method in cases when you dont want this activity to load again and again when the user presses back button.

Basically it clears the activity from the. In addition to rommex answer above, I have also noticed that finish does queue the destruction of the Activity and that it depends on Activity priority. If I call finish after onStop , I don't see onDestroy until 5 minutes later. In summary, onDestroy is never guaranteed to be called, but even in the case it is called, it could be delayed. Various answers and notes are claiming that finish can skip onPause and onStop and directly execute onDestroy.

So I wrote this mini-app below which logs each state upon entry. It includes a button which calls finish -- so you can see the logs of which methods get fired.

This experiment would suggested that finish does indeed also call onPause and onStop. Here is the output I get:. The diagram does not show any straight path from [Activity Running] to [ onDestroy ] caused by the system.

My study shows that finish method actually places some destruction operations in the queue, but the Activity is not destroyed immediately. The destruction is scheduled though. For example, if you place finish in onActivityResult callback, while onResume has yet to run, then first onResume will be executed, and only after that onStop and onDestroy are called. NOTE: onDestroy may not be called at all, as stated on the documentation. The finish operation will not even begin until you return control to Android.

It seems that the only correct answer here so far has been given by romnex: "onDestroy may not be called at all". Even though in practice, in almost all cases it will, there is no guarantee: The documentation on finish only promises that the result of the activity is propagated back to the caller, but nothing more.

Moreover, the lifecycle documentation clarifies that the activity is killable by the OS as soon as onStop finishes or even earlier on older devices , which, even though unlikely and therefore rare to observe in a simple test, might mean that the activity might be killed while or even before onDestroy is executed.

How to use onPause method in android. Skip to content Android Windows Linux Apple. Home » Android. See also Where are downloads on my Android phone? What is the purpose of super onCreate in android?

What is onCreate method in Android? Best answer: What is difference between intent and intent filter in Android? When onDestroy is called before onPause and onStop in an Android application?

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