bug fix: fragments are duplicated and overlaped

[zdsfwy]

Hi, professor.
In FragmentProgrammaticLayout, the main Activity would add fragment whenever onCreate is invoked. As a result, when onCreate is invoked by configuration changing, duplicated fragments would be added and overlapped.
Here are the screenshots.Before configuration change:

After configuration change(since new fragment is overlapped with old fragment, multiple items in the list appear to be selected):

[JoelEspinal]

Hi, Good Afternoon.
My name is Joel.

I don't understanding your fix completely.

If this was your solution I appreciate some lite explanation about it. ;)

I think the Issue is about Fragment lifecycle.
maybe you can find a more appropriate solution on that way.

Thanks for your time,

Joel Espinal (JoelEspinal)
Developer

here a part snipped code:

if(savedInstanceState != null) {

•      return;
  

•  }
  

[zdsfwy]

Hi, Joel. Thank you for reply.

Sorry for leading to confusing. Let me explain if(savedInstanceState != null) { return; } .

When configuration(such as orientation) changes, android system would restart the app. Before restart, it would save certain information into savedInstanceState, and pass it as parameter to onCreate method. If savedInstanceState is not null, it means this is not a newly created app, but restarted app. Since in this example FragmentProgrammaticLayout , fragments are only needed to be added once when the app is newly created, they don't need to be added again when restarted. So, it should just directly return.

Here is the link from google android site, where it uses exactly the same technique.