OnRestart vs. OnResume - Android Lifecycle Question

android events lifecycle
jondavidjohn picture jondavidjohn · Jun 28, 2011 · Viewed 21.1k times · Source

My end-goal is to have an application that runs a block of code when it (the application, not the activity) is opened up after being left ( back from home screen, etc... )

According to the Activity Lifecycle, this should be the onRestart() event on a per activity basis ( at least how I interpret it )

Both onRestart() and onResume() are being called whether I am returning to the Activity within the application (back button) AND when the app is called back up.

Given this diagram enter image description here

I am interpreting it this way:

  • RED = movement between activities within the application
  • BLUE = moving to an activity outside the Application

Is my understanding incorrect?

EDIT (Clarifying specific use case)

I'm attempting to use onRestart() to replicate some security logic (PIN Validation) found in onCreate(), but it's being called even when I press the back button inside the application...

Answer

Nick Campion picture Nick Campion · Jun 28, 2011

My observation is that its hard to tie the lifecycle events to user behavior on the device or emulator. Where your app is paused, if the device needs memory or wants to recover resources, it will terminate the activity, causing onCreate to be called. There is just too many scenarios to build an adequate state machine to tell yourself "how" or "why" your activity was terminated.

The only way I've found to manage this is to create a service to hold the application state and manually manage the state. The problem is trying to use the Activity state to manage the application state. The Activity design seems to have limitations that just make it a poor choice for achieving the goal you've stated.

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