1+ /*
2+ * Copyright 2023-2025 wintmain
3+ *
4+ * Licensed under the Apache License, Version 2.0 (the "License");
5+ * you may not use this file except in compliance with the License.
6+ * You may obtain a copy of the License at
7+ *
8+ * https://www.apache.org/licenses/LICENSE-2.0
9+ *
10+ * Unless required by applicable law or agreed to in writing, software
11+ * distributed under the License is distributed on an "AS IS" BASIS,
12+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13+ * See the License for the specific language governing permissions and
14+ * limitations under the License.
15+ */
16+
17+ package com .wintmain .wBasis .transition ;
18+
19+ import android .os .Bundle ;
20+ import android .transition .TransitionInflater ;
21+ import android .view .LayoutInflater ;
22+ import android .view .View ;
23+ import android .view .View .OnLayoutChangeListener ;
24+ import android .view .ViewGroup ;
25+ import androidx .annotation .NonNull ;
26+ import androidx .annotation .Nullable ;
27+ import androidx .core .app .SharedElementCallback ;
28+ import androidx .fragment .app .Fragment ;
29+ import androidx .recyclerview .widget .RecyclerView ;
30+ import com .wintmain .wBasis .R ;
31+ import com .wintmain .wBasis .transition .adapter .GridAdapter ;
32+
33+ import java .util .List ;
34+ import java .util .Map ;
35+
36+ /**
37+ * A fragment for displaying a grid of images.
38+ */
39+ public class GridToPagerFragment extends Fragment {
40+
41+ private RecyclerView recyclerView ;
42+
43+ @ Nullable
44+ @ Override
45+ public View onCreateView (@ NonNull LayoutInflater inflater , @ Nullable ViewGroup container ,
46+ @ Nullable Bundle savedInstanceState ) {
47+ recyclerView = (RecyclerView ) inflater .inflate (R .layout .fragment_grid_to_pager , container ,
48+ false );
49+ recyclerView .setAdapter (new GridAdapter (this ));
50+
51+ prepareTransitions ();
52+ postponeEnterTransition ();
53+
54+ return recyclerView ;
55+ }
56+
57+ @ Override
58+ public void onViewCreated (@ NonNull View view , @ Nullable Bundle savedInstanceState ) {
59+ super .onViewCreated (view , savedInstanceState );
60+ scrollToPosition ();
61+ }
62+
63+ /**
64+ * Scrolls the recycler view to show the last viewed item in the grid. This is important when
65+ * navigating back from the grid.
66+ */
67+ private void scrollToPosition () {
68+ recyclerView .addOnLayoutChangeListener (new OnLayoutChangeListener () {
69+ @ Override
70+ public void onLayoutChange (View v ,
71+ int left ,
72+ int top ,
73+ int right ,
74+ int bottom ,
75+ int oldLeft ,
76+ int oldTop ,
77+ int oldRight ,
78+ int oldBottom ) {
79+ recyclerView .removeOnLayoutChangeListener (this );
80+ final RecyclerView .LayoutManager layoutManager = recyclerView .getLayoutManager ();
81+ View viewAtPosition = layoutManager .findViewByPosition (
82+ GridToPagerMainActivity .currentPosition );
83+ // Scroll to position if the view for the current position is null (not currently
84+ // part of
85+ // layout manager children), or it's not completely visible.
86+ if (viewAtPosition == null || layoutManager
87+ .isViewPartiallyVisible (viewAtPosition , false , true )) {
88+ recyclerView .post (() -> layoutManager .scrollToPosition (
89+ GridToPagerMainActivity .currentPosition ));
90+ }
91+ }
92+ });
93+ }
94+
95+ /**
96+ * Prepares the shared element transition to the pager fragment, as well as the other
97+ * transitions
98+ * that affect the flow.
99+ */
100+ private void prepareTransitions () {
101+ setExitTransition (TransitionInflater .from (getContext ())
102+ .inflateTransition (R .transition .grid_exit_transition ));
103+
104+ // A similar mapping is set at the ImagePagerFragment with a setEnterSharedElementCallback.
105+ setExitSharedElementCallback (
106+ new SharedElementCallback () {
107+ @ Override
108+ public void onMapSharedElements (List <String > names ,
109+ Map <String , View > sharedElements ) {
110+ // Locate the ViewHolder for the clicked position.
111+ RecyclerView .ViewHolder selectedViewHolder = recyclerView
112+ .findViewHolderForAdapterPosition (
113+ GridToPagerMainActivity .currentPosition );
114+ if (selectedViewHolder == null ) {
115+ return ;
116+ }
117+
118+ // Map the first shared element name to the child ImageView.
119+ sharedElements
120+ .put (names .get (0 ),
121+ selectedViewHolder .itemView .findViewById (R .id .card_image ));
122+ }
123+ });
124+ }
125+ }
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