Prevent activity from reload after rotation in xamarin, monodroid

Question

Ok... So my problem is to prevent from activity to reload after orientation is changed. Basically, what I did is this:

[Activity(Label = \"migs\", ConfigurationC         


        

Answer 1

Above API 13, you need to include screensize in your ConfigChanges.

As denoted here.

Maybe adding that tag to your activity for API13+ will help?

Answer 2

what happen when orientation change (consider you enable rotation in your phone) ?

Android restart activity onDestroy() is called, followed by onCreate() , you can distinguish between onDestroy() call to kill activity or restart app throw old answer.

Prevent Activity restart

just set ConfigurationChanges to both Orientation , ScreenSize

[Activity (Label = "CodeLayoutActivity", ConfigurationChanges=Android.Content.PM.ConfigChanges.Orientation | Android.Content.PM.ConfigChanges.ScreenSize)]

why this may be not working ?

I dont think this will not working but set RetaintInstance to true read more about RetainInstance

class myFragment: Fragment
    {

        public override void OnCreate(Bundle savedInstanceState)
        {
            base.OnCreate(savedInstanceState);
            this.RetainInstance = true;
          // this to change screen orientation 
            Activity.RequestedOrientation = ScreenOrientation.Landscape;


        }

       .....

}

hope this help

Answer 3

Ok... At last I solved it! :) Saving activity state instead of preventing activity from reload, from first sight can seem to be a little tricky, but in fact is really easy and it's the best solution for situations like this. In my case, I had a ListView, that populates from the internet with items, that stored in custom list adapter. If device orientation was changed, the activity was reloaded, so does the ListView, and I was loosing all the data. All I needed to do is to override the OnRetainNonConfigurationInstance method. Here's a quick sample of how to do it.
First of all, we need a class, that can handle all of our stuff.

Here is a wrapper for all the things we need to save:

public class MainListAdapterWrapper : Java.Lang.Object
{
    public Android.Widget.IListAdapter Adapter { get; set; }
    public int Position { get; set; }
    public List<YourObject> Items { get; set; }
}

In our activity, we need to hold variables, to store all the data:

ListView _listView; //Our ListView
List<YourObject> _yourObjectList; //Our items collection
MainListAdapterWrapper _listBackup; //The instance of the saving state wrapper
MainListAdapter _mListAdapter; //Adapter itself

Then, we overriding the OnRetainNonConfigurationInstance method in the activity:

public override Java.Lang.Object OnRetainNonConfigurationInstance()
{
    base.OnRetainNonConfigurationInstance();
    var adapterWrapper = new MainListAdapterWrapper();
    adapterWrapper.Position = this._mListAdapter.CurrentPosition; //I'll explain later from where this came from
    adapterWrapper.Adapter = this._listView.Adapter;
    adapterWrapper.Items = this._yourObjectList;
    return adapterWrapper;
}

And the final stage is to load saved state in OnCreate method:

protected override void OnCreate(Bundle bundle)
{
    base.OnCreate(bundle);
    SetContentView(Resource.Layout.list);

    this._listView = FindViewById<ListView>(Resource.Id.listView);

    if (LastNonConfigurationInstance != null)
    {
        this._listBackup = LastNonConfigurationInstance as MainListAdapterWrapper;
        this._yourObjectList = this._listBackup.Items;
        this._mListAdapter = this._listBackup.Adapter as MainListAdapter;
        this._listView.Adapter = this._mListAdapter;

        //Scrolling to the last position
        if(this._listBackup.Position > 0)
            this._listView.SetSelection(this._listBackup.Position);
    }
    else
    {
        this._listBackup = new MainListAdapterWrapper();
        //Here is the regular loading routine
    }

}

And about the this._mListAdapter.CurrentPosition... In my MainListAdapter, I added this property:

public int CurrentPosition { get; set; }

And the, in the `GetView' method, I did that:

this.CurrentPosition = position - 2;

---

P.S.

You don't have to implement exactly as I showed here. In this code, I'm holding a lot of variables, and making all the routine inside the OnCreate method - that is wrong. I did that, just to show how it can be implemented.