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Here is a situation. I want to navigate from Fragment A-> B-> C.
In B Fragment there is listview. On item click I open the detail view C Fragment. Ofcourse I used replace method and added addtoBackStack(null) while transactiong from B to C so that on Back press it returned to B.
All goes well. But when I return to B from C, the view is being refreshed and hence the webservice is being called again. I don't want to do this. I want to retain the B Fragment state with listview.
I got some post of Retain Instance, but it didn't help that much.
Any help is much appreciated.
Thanks.
229
Various Android system operations can affect the state of your fragment. To ensure the user's state is saved, the Android framework automatically saves and restores the fragments and the back stack. Therefore, you need to ensure that any data in your fragment is saved and restored as well.
// Save the ListView state (= includes scroll position) as a Parceble Parcelable state = listView. onSaveInstanceState(); // e.g. set new items listView. setAdapter(adapter); // Restore previous state (including selected item index and scroll position) listView.
The savedInstanceState is a reference to a Bundle object that is passed into the onCreate method of every Android Activity. Activities have the ability, under special circumstances, to restore themselves to a previous state using the data stored in this bundle.
Use replace() to replace an existing fragment in a container with an instance of a new fragment class that you provide. Calling replace() is equivalent to calling remove() with a fragment in a container and adding a new fragment to that same container. transaction. commit();
As explained here you can use onSaveInstanceState() to save data in the Bundle and retrieve that data in the onRestoreInstanceState() method.
Often setRetainState(true) is mentioned as way to keep the ui state in fragment, but it does not work for you because you are using the backstack.
So a good way for you could be to save the scrollposition in onSaveInstanceState() and restore it in onRestoreInstanceState() like this:
public class MyListFragment extends ListFragment {
@Override
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
int index = this.getListView().getFirstVisiblePosition();
View v = this.getListView().getChildAt(0);
int top = (v == null) ? 0 : v.getTop();
outState.putInt("index", index);
outState.putInt("top", top);
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
[...]
if (savedInstanceState != null) {
// Restore last state for checked position.
index = savedInstanceState.getInt("index", -1);
top = savedInstanceState.getInt("top", 0);
}
if(index!=-1){
this.getListView().setSelectionFromTop(index, top);
}
}
Further more you can find a more detailed similiar example here.
94
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