CODEWITHSUNDEEP
javaandroidperformanceandroid-activityandroid-lifecycle
Lew Wei Hao
Lew Wei Hao

Reputation: 843

Are Android Activity life cycle methods useful even when no code is specified for them?

I understand when these methods are called: onCreate(), onStart(), onResume(), onPause(), onStop(), onDestroy().

However, will these methods actually do anything by default even if I didn't write any code in them?

For example, when the onPause method is called, will it automatically help me to pause and save resources even if I didn't specify the code for doing so? Or must I code everything manually?

If so, what is the general guideline of what kind of resources to save during OnPause and OnStop?

Upvotes: 3

Views: 177

Answers (2)

Michele Lacorte
Michele Lacorte

Reputation: 5363

Refer to Activity Lifecycle

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onCreate() Called when the activity is first created. This is where you should do all of your normal static set up: create views, bind data to lists, etc. This method also provides you with a Bundle containing the activity's previously frozen state, if there was one. Always followed by onStart().

onRestart() Called after your activity has been stopped, prior to it being started again. Always followed by onStart()

onStart() Called when the activity is becoming visible to the user. Followed by onResume() if the activity comes to the foreground, or onStop() if it becomes hidden.

onResume() Called when the activity will start interacting with the user. At this point your activity is at the top of the activity stack, with user input going to it. Always followed by onPause().

onPause() Called when the system is about to start resuming a previous activity. This is typically used to commit unsaved changes to persistent data, stop animations and other things that may be consuming CPU, etc. Implementations of this method must be very quick because the next activity will not be resumed until this method returns. Followed by either onResume() if the activity returns back to the front, or onStop() if it becomes invisible to the user.

onStop() Called when the activity is no longer visible to the user, because another activity has been resumed and is covering this one. This may happen either because a new activity is being started, an existing one is being brought in front of this one, or this one is being destroyed. Followed by either onRestart() if this activity is coming back to interact with the user, or onDestroy() if this activity is going away.

onDestroy() The final call you receive before your activity is destroyed. This can happen either because the activity is finishing (someone called finish() on it, or because the system is temporarily destroying this instance of the activity to save space. You can distinguish between these two scenarios with the isFinishing() method.

Upvotes: 1

Francisco Hernandez
Francisco Hernandez

Reputation: 2468

You MUST code those events if you want to do something inside your app. The activity lifeclycle (activity lifecycle part) will do tasks related to the android system, besides, the activity lifecycle give to you the opportunity to do things on your own when the events happens, but is up to you and your code to do things for your app.

If the only thing that you want to achieve is save/restore data you can use onSaveInstanceState. Take a look here How to use onSavedInstanceState example please

Upvotes: 1

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