Android：片段会导致方向改变的问题

Question

According to the Google example here I developed an app based on fragments.

My main activity contains a listfragment of titles and, if it is created in landscape mode, a details fragment. If the app is startet in portrait mode, the main activity contains only the listfragment and, if a list item is clicked, start a new activity which shows the detailsfragment.

If I stay in either the portrait or landscape mode, everything works fine. But as soon as I change the orientation multiple problems occur.

1st problem: starting in portrait mode, then changing to landscape mode, the activity is added to the activity stack twice and I have to press the back button twice to close my app. I cant image this is the way Google wants this to work, so how do I avoid this?

2nd problem: when changing from landscape mode to portait mode, the list is shown and not the detailsfragment with the currently selected item. Therefore, all the user input in my detailsfragment is lost. This is just annoying and I don't know how to handle this. Do I have to care about the orientation change programmatically in every activity?

3rd problem: When I switch between n details in landscape mode, as soon as I change to portrait mode, I have to press the back button n times to close my add as the fragments are in the back stack (although they aren't visible any more). Do I have to clean the back stack myself in orientation change?

Answer 1

There is one thing about Activities. That is, when you change the orientation, the Activity restarts unless you do the following:

-First, add this in your manifest (inside the activity tag), so you will be able to tell the application what to do in case you change the orientation:

android:configChanges="orientation"

-Second, implement the following method in case you need to to something in case the orientation changes. If not, with the one before the user won't loose its data.

onOrientationChanged (int orientation)