protected virtual MvxViewPagerFragmentInfo FindFragmentInfoFromAttribute(
MvxFragmentPresentationAttribute attribute, MvxCachingFragmentStatePagerAdapter adapter)
{
MvxViewPagerFragmentInfo fragmentInfo = null;
if (attribute.Tag != null)
{
fragmentInfo = adapter.FragmentsInfo.FirstOrDefault(f => f.Tag == attribute.Tag);
}
if (fragmentInfo != null)
{
return(fragmentInfo);
}
bool IsMatch(MvxViewPagerFragmentInfo info)
{
if (attribute.ViewType == null)
{
return(false);
}
var viewTypeMatches = info.FragmentType == attribute.ViewType;
if (attribute.ViewModelType != null)
{
return(viewTypeMatches && info.ViewModelType == attribute.ViewModelType);
}
return(viewTypeMatches);
}
fragmentInfo = adapter.FragmentsInfo.FirstOrDefault(IsMatch);
return(fragmentInfo);
}
private void RestoreFragmentsInfoState(Bundle bundle)
{
if (bundle == null)
{
return;
}
var fragmentInfoParcelables = bundle.GetParcelableArray(_bundleFragmentsInfoKey);
if (fragmentInfoParcelables == null)
{
return;
}
// First, we create a list of the ViewPager fragments that were restored by Android.
var fragments = GetFragmentsFromBundle(bundle);
// Now we get the FragmentInfo data for each fragment from the bundle.
int i = 0;
foreach (ViewPagerFragmentInfoParcelable parcelable in fragmentInfoParcelables)
{
MvxViewPagerFragmentInfo fragInfo = null;
if (i < fragments.Count)
{
var f = fragments[i];
if (f is IMvxFragmentView fragment && fragment.ViewModel != null)
{
// The fragment was already restored by Android with its old ViewModel (cached by MvvmCross).
// Add the ViewModel to the FragmentInfo object so the adapter won't instantiate a new one.
var viewModelInstanceRequest = new MvxViewModelInstanceRequest(fragment.ViewModel);
fragInfo = new MvxViewPagerFragmentInfo(parcelable.Title, parcelable.Tag, parcelable.FragmentType, viewModelInstanceRequest);
}
}
if (fragInfo == null)
{
// Either the fragment doesn't exist or it doesn't have a ViewModel.
// Fall back to a FragmentInfo with the ViewModelType. The adapter will create a ViewModel in GetItem where we will add it to the FragmentInfo.
var viewModelRequest = new MvxViewModelRequest(parcelable.ViewModelType);
fragInfo = new MvxViewPagerFragmentInfo(parcelable.Title, parcelable.Tag, parcelable.FragmentType, viewModelRequest);
}
FragmentsInfo.Add(fragInfo);
i++;
}
NotifyDataSetChanged();
}
public override Fragment GetItem(int position, Fragment.SavedState fragmentSavedState = null)
{
var fragment = base.GetItem(position, fragmentSavedState);
// If the MvxViewPagerFragmentInfo for this position doesn't have the ViewModel, overwrite it with a new MvxViewPagerFragmentInfo that has the ViewModel we just created.
// Not doing this means the ViewModel gets recreated every time the Fragment gets recreated!
if (FragmentsInfo != null && FragmentsInfo.Count > position && fragment is IMvxFragmentView mvxFragment && mvxFragment.ViewModel != null)
{
var oldFragInfo = FragmentsInfo[position];
if (oldFragInfo != null && oldFragInfo.ViewModel == null)
{
var newFragInfo = new MvxViewPagerFragmentInfo(oldFragInfo.Title, oldFragInfo.Tag, oldFragInfo.FragmentType, mvxFragment.ViewModel);
FragmentsInfo[position] = newFragInfo;
}
}
return(fragment);
}
protected virtual Task <bool> ShowViewPagerFragment(
Type view,
MvxViewPagerFragmentPresentationAttribute attribute,
MvxViewModelRequest request)
{
ValidateArguments(view, attribute, request);
// if the attribute doesn't supply any host, assume current activity!
if (attribute.FragmentHostViewType == null && attribute.ActivityHostViewModelType == null)
{
attribute.ActivityHostViewModelType = GetCurrentActivityViewModelType();
}
ViewPager? viewPager = null;
FragmentManager?fragmentManager = null;
// check for a ViewPager inside a Fragment
if (attribute.FragmentHostViewType != null)
{
var fragment = GetFragmentByViewType(attribute.FragmentHostViewType);
if (fragment == null)
{
throw new MvxException("Fragment not found", attribute.FragmentHostViewType.Name);
}
if (fragment.View == null)
{
throw new MvxException("Fragment.View is null. Please consider calling Navigate later in your code",
attribute !.FragmentHostViewType.Name);
}
viewPager = fragment.View.FindViewById <ViewPager>(attribute.ViewPagerResourceId);
fragmentManager = fragment.ChildFragmentManager;
}
// check for a ViewPager inside an Activity
if (attribute.ActivityHostViewModelType != null)
{
var currentActivityViewModelType = GetCurrentActivityViewModelType();
// if the host Activity is not the top-most Activity, then show it before proceeding, and return false for now
if (attribute.ActivityHostViewModelType != currentActivityViewModelType)
{
PendingRequest = request;
ShowHostActivity(attribute);
return(Task.FromResult(false));
}
if (CurrentActivity.IsActivityAlive())
{
viewPager = CurrentActivity !.FindViewById <ViewPager>(attribute.ViewPagerResourceId);
}
fragmentManager = CurrentFragmentManager;
}
// no more cases to check. Just throw if ViewPager wasn't found
if (viewPager == null)
{
throw new MvxException("ViewPager not found");
}
var tag = attribute.Tag ?? attribute.ViewType.FragmentJavaName();
var fragmentInfo = new MvxViewPagerFragmentInfo(attribute.Title, tag, attribute.ViewType, request);
if (viewPager.Adapter is MvxCachingFragmentStatePagerAdapter adapter)
{
adapter.FragmentsInfo.Add(fragmentInfo);
adapter.NotifyDataSetChanged();
}
else
{
viewPager.Adapter = new MvxCachingFragmentStatePagerAdapter(
CurrentActivity,
fragmentManager,
new List <MvxViewPagerFragmentInfo>
{
fragmentInfo
}
);
}
return(Task.FromResult(true));
}
