android - How to restore fragment state after resume w/o savedInstanceState? -


in app fragmentactivity contains simple listfragment , want preserve position user has scrolled to. did following:

private int initialscrollposition = 0; private int initialscrollyoffset = 0;  @override public void onsaveinstancestate (bundle outstate) {     outstate.putint(scroll_position, this.getlistview().getfirstvisibleposition());     view firstvisibleitemview = this.getlistview().getchildat(0);     outstate.putint(scroll_y_offset, (firstvisibleitemview == null) ? 0 : firstvisibleitemview.gettop()); }  @override public void onactivitycreated (bundle savedinstancestate) {     super.onactivitycreated(savedinstancestate);     this.restorestate(savedinstancestate); }  private void restorestate(bundle savedinstancestate) {     if(savedinstancestate != null             && savedinstancestate.containskey(scroll_position)) {         this.initialscrollposition = savedinstancestate.getint(scroll_position);     }     if(savedinstancestate != null             && savedinstancestate.containskey(scroll_y_offset)) {         this.initialscrollyoffset = savedinstancestate.getint(scroll_y_offset);     } }  @override public void onstart () {     super.onstart();     // other gui stuff     this.getlistview().setselectionfromtop(this.initialscrollposition, this.initialscrollyoffset); }

this solution works fine things display orientation changes or moving 1 activity of app next.

but if fire app, scroll bit, go home, , restore app recents, onactivitycreated (or other callbacks savedinstancestate bundle) not called , therefore state cannot restored.

therefore have 2 questions:

  1. what can savedinstancestate after resuming without onxxxcreated callbacks?
  2. what lifecycle doing there. i'd understand, why approach fails.

thank insight!

solution:

thx andré! changed onsaveinstancestate this:

@override public void onsaveinstancestate (bundle outstate) {     this.initialscrollposition = this.getlistview().getfirstvisibleposition();     view firstvisibleitemview = this.getlistview().getchildat(0);     this.initialscrollyoffset = (firstvisibleitemview == null) ? 0 : firstvisibleitemview.gettop();     outstate.putint(scroll_position, this.initialscrollposition);     outstate.putint(scroll_y_offset, this.initialscrollyoffset); }

if app brought front using recent apps button, might isn't recreated, because system didn't finish yet. in case onresume() , following callbacks invoked.

conclusion: try restore position in onresume(), store positions in onpause() (for recent app switches activity isn't recreated), extract positions savedinstancestate bundle (for orientation change activity recreated).


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