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#275 Correct fragment tracking for correct GetLastFragmentInfo in MvxCachingFragmentCompatActivity #297

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#275 Correct fragment tracking for correct GetLastFragmentInfo in MvxCachingFragmentCompatActivity #297

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79 changes: 69 additions & 10 deletions MvvmCross.Droid.Support.V7.AppCompat/MvxCachingFragmentCompatActivity.cs
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Expand Up @@ -17,7 +17,6 @@
using MvvmCross.Platform;
using MvvmCross.Platform.Exceptions;
using MvvmCross.Platform.Platform;
using MvvmCross.Binding.Droid.BindingContext;
using MvvmCross.Droid.Platform;
using MvvmCross.Droid.Views;
using MvvmCross.Core.ViewModels;
Expand All @@ -26,6 +25,7 @@
using MvvmCross.Droid.Shared.Presenter;
using MvvmCross.Droid.Shared.Attributes;
using MvvmCross.Droid.Shared.Fragments;
using MvvmCross.Droid.Support.V4;

namespace MvvmCross.Droid.Support.V7.AppCompat
{
Expand All @@ -34,7 +34,10 @@ public class MvxCachingFragmentCompatActivity : MvxAppCompatActivity, IFragmentC
{
public const string ViewModelRequestBundleKey = "__mvxViewModelRequest";
private const string SavedFragmentTypesKey = "__mvxSavedFragmentTypes";
private const string SavedTagBackStack = "__mvxSavedTagBackStack";

private IFragmentCacheConfiguration _fragmentCacheConfiguration;
private readonly Stack<string> _tagBackStack = new Stack<string>();

public override View OnCreateView(View parent, string name, Context context, IAttributeSet attrs)
{
Expand Down Expand Up @@ -119,6 +122,21 @@ private void RestoreFragmentsCache()
}
}

private void RestoreTagBackStackFromBundle(IMvxJsonConverter serializer, Bundle savedInstanceState)
{
var savedTagBackStackJson = savedInstanceState.GetString(SavedTagBackStack);
if (!string.IsNullOrEmpty(savedTagBackStackJson))
{
var savedReversedTagBackStackState = serializer.DeserializeObject<string[]>(savedTagBackStackJson);

_tagBackStack.Clear();
for (int i = 0; i < savedReversedTagBackStackState.Length; i++)
{
_tagBackStack.Push(savedReversedTagBackStackState[i]);
}
}
}

private Dictionary<string, Type> CreateFragmentTypesDictionary(Bundle outState)
{
IMvxSavedStateConverter savedStateConverter;
Expand Down Expand Up @@ -157,7 +175,19 @@ protected override void OnSaveInstanceState(Bundle outState)
{
base.OnSaveInstanceState(outState);
IMvxJsonConverter ser;
if (FragmentCacheConfiguration.HasAnyFragmentsRegisteredToCache && Mvx.TryResolve(out ser))
if (!Mvx.TryResolve(out ser))
{
return;
}

if (_tagBackStack.Any())
{
var reversedTagBackStack = _tagBackStack.Reverse().ToArray();
var json = ser.SerializeObject(reversedTagBackStack);
outState.PutString(SavedTagBackStack, json);
}

if (FragmentCacheConfiguration.HasAnyFragmentsRegisteredToCache)
{
FragmentCacheConfiguration.SaveFragmentCacheConfigurationState(outState, ser);

Expand Down Expand Up @@ -208,9 +238,10 @@ protected virtual void ShowFragment(string tag, int contentId, Bundle bundle, bo
//If we already have a previously created fragment, we only need to send the new parameters
if (fragInfo.CachedFragment != null && fragmentReplaceMode == FragmentReplaceMode.ReplaceFragment)
{
(fragInfo.CachedFragment as Fragment).Arguments.Clear();
(fragInfo.CachedFragment as Fragment).Arguments.PutAll(bundle);
}
var fragment = fragInfo.CachedFragment.ToFragment();
fragment.Arguments.Clear();
fragment.Arguments.PutAll(bundle);
}
else
{
//Otherwise, create one and cache it
Expand All @@ -222,6 +253,8 @@ protected virtual void ShowFragment(string tag, int contentId, Bundle bundle, bo
currentFragment = fragInfo.CachedFragment as Fragment;
ft.Replace(fragInfo.ContentId, fragInfo.CachedFragment as Fragment, fragInfo.Tag);

_tagBackStack.Push(fragInfo.Tag);

//if replacing ViewModel then clear the cache after the fragment
//has been added to the transaction so that the Tag property is not null
//and the UniqueImmutableCacheTag property (if not overridden) has the correct value
Expand Down Expand Up @@ -277,6 +310,9 @@ public override void OnBackPressed()
{
if (SupportFragmentManager.BackStackEntryCount >= 1)
{
var backStackEntry = SupportFragmentManager.GetBackStackEntryAt(SupportFragmentManager.BackStackEntryCount - 1);
RemoveFromTagBackStack(backStackEntry.Name);

SupportFragmentManager.PopBackStackImmediate();

if (FragmentCacheConfiguration.EnableOnFragmentPoppedCallback)
Expand All @@ -289,6 +325,7 @@ public override void OnBackPressed()
return;
}

_tagBackStack.Clear();
base.OnBackPressed();
}

Expand All @@ -311,12 +348,12 @@ protected virtual IEnumerable<Fragment> GetCurrentCacheableFragments()

protected virtual IMvxCachedFragmentInfo GetLastFragmentInfo()
{
var currentCacheableFragments = GetCurrentCacheableFragments().ToList();
if (!currentCacheableFragments.Any())
if (!_tagBackStack.Any())
{
throw new InvalidOperationException("Cannot retrieve last fragment as FragmentManager is empty.");
}

var lastFragment = currentCacheableFragments.Last();
var tagFragment = GetTagFromFragment(lastFragment);
var tagFragment = _tagBackStack.Peek();

return GetFragmentInfoByTag(tagFragment);
}
Expand Down Expand Up @@ -351,7 +388,9 @@ protected override void OnCreate (Bundle bundle)
return;
}

FragmentCacheConfiguration.RestoreCacheConfiguration(bundle, serializer);
RestoreTagBackStackFromBundle(serializer, bundle);

FragmentCacheConfiguration.RestoreCacheConfiguration(bundle, serializer);
// Gabriel has blown his trumpet. Ressurect Fragments from the dead.
RestoreFragmentsCache();

Expand Down Expand Up @@ -389,6 +428,7 @@ protected virtual void CloseFragment(string tag, int contentId)
var frag = SupportFragmentManager.FindFragmentById(contentId);
if (frag == null) return;

RemoveFromTagBackStack(frag.Tag);
SupportFragmentManager.PopBackStackImmediate(tag, 1);
}

Expand Down Expand Up @@ -456,6 +496,7 @@ public virtual bool Close(IMvxViewModel viewModel)
{
if (SupportFragmentManager.BackStackEntryCount == 0)
{
_tagBackStack.Clear();
base.OnBackPressed();
return true;
}
Expand All @@ -471,6 +512,24 @@ public virtual bool Close(IMvxViewModel viewModel)
CloseFragment(frag.Tag, frag.ContentId);
return true;
}

private void RemoveFromTagBackStack(string tag)
{
// reverse to more logical order
var tagBackStack = _tagBackStack.Reverse().ToList();

// remove tag
var firstFoundTagIndex = tagBackStack.FindIndex(backStackTag => backStackTag == tag);
if (firstFoundTagIndex > 0)
tagBackStack.RemoveAt(firstFoundTagIndex);

// hard reset and reinitialize _tagBackStack
_tagBackStack.Clear();
for (var i = 0; i < tagBackStack.Count; i++)
{
_tagBackStack.Push(tagBackStack[i]);
}
}
}

public abstract class MvxCachingFragmentCompatActivity<TViewModel>
Expand Down