Work around incompatibility between AndroidFastScroll and recyclerview-selection (#721)

* Work around incompatibility between AndroidFastScroll and recyclerview-selection

* move hacked recyclerview into separate package

Signed-off-by: Harsh Shandilya <me@msfjarvis.dev>

* Make RecyclerViewHelper private static

Co-authored-by: Harsh Shandilya <me@msfjarvis.dev>

3 files changed, 344 insertions, 6 deletions

diff --git a/app/src/main/java/androidx/recyclerview/widget/FixOnItemTouchDispatchRecyclerView.java b/app/src/main/java/androidx/recyclerview/widget/FixOnItemTouchDispatchRecyclerView.java
new file mode 100644
index 00000000..58590a66
--- /dev/null
+++ b/app/src/main/java/androidx/recyclerview/widget/FixOnItemTouchDispatchRecyclerView.java
@@ -0,0 +1,341 @@
+/*
+ * Copyright 2020 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package androidx.recyclerview.widget;
+
+import android.annotation.SuppressLint;
+import android.content.Context;
+import android.graphics.Canvas;
+import android.graphics.Rect;
+import android.util.AttributeSet;
+import android.view.MotionEvent;
+import android.view.View;
+
+import androidx.annotation.AttrRes;
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+import androidx.recyclerview.widget.GridLayoutManager;
+import androidx.recyclerview.widget.LinearLayoutManager;
+import androidx.recyclerview.widget.RecyclerView;
+
+import me.zhanghai.android.fastscroll.FastScroller;
+import me.zhanghai.android.fastscroll.PopupTextProvider;
+import me.zhanghai.android.fastscroll.Predicate;
+import me.zhanghai.android.fastscroll.ViewHelperProvider;
+
+public class FixOnItemTouchDispatchRecyclerView extends RecyclerView implements ViewHelperProvider {
+
+    @NonNull
+    private final ViewHelper mViewHelper = new ViewHelper(this);
+
+    @Nullable
+    private OnItemTouchListener mPhantomOnItemTouchListener = null;
+    private OnItemTouchListener mInterceptingOnItemTouchListener = null;
+
+    public FixOnItemTouchDispatchRecyclerView(@NonNull Context context) {
+        super(context);
+    }
+
+    public FixOnItemTouchDispatchRecyclerView(@NonNull Context context,
+                                              @Nullable AttributeSet attrs) {
+        super(context, attrs);
+    }
+
+    public FixOnItemTouchDispatchRecyclerView(@NonNull Context context,
+                                              @Nullable AttributeSet attrs,
+                                              @AttrRes int defStyleAttr) {
+        super(context, attrs, defStyleAttr);
+    }
+
+    @NonNull
+    @Override
+    public FastScroller.ViewHelper getViewHelper() {
+        return mViewHelper;
+    }
+
+    @Override
+    public boolean onInterceptTouchEvent(MotionEvent e) {
+        mInterceptingOnItemTouchListener = null;
+        if (findInterceptingOnItemTouchListener(e)) {
+            cancelScroll();
+            return true;
+        }
+        return super.onInterceptTouchEvent(e);
+    }
+
+    @SuppressLint("ClickableViewAccessibility")
+    @Override
+    public boolean onTouchEvent(MotionEvent e) {
+        if (dispatchOnItemTouchListeners(e)) {
+            cancelScroll();
+            return true;
+        }
+        return super.onTouchEvent(e);
+    }
+
+    @Override
+    public void requestDisallowInterceptTouchEvent(boolean disallowIntercept) {
+        if (mPhantomOnItemTouchListener != null) {
+            mPhantomOnItemTouchListener.onRequestDisallowInterceptTouchEvent(disallowIntercept);
+        }
+        super.requestDisallowInterceptTouchEvent(disallowIntercept);
+    }
+
+    private void cancelScroll() {
+        MotionEvent syntheticCancel = MotionEvent.obtain(
+                0, 0, MotionEvent.ACTION_CANCEL, 0f, 0f, 0);
+        super.onInterceptTouchEvent(syntheticCancel);
+        syntheticCancel.recycle();
+    }
+
+    private boolean dispatchOnItemTouchListeners(@NonNull MotionEvent e) {
+        if (mInterceptingOnItemTouchListener == null) {
+            if (e.getAction() == MotionEvent.ACTION_DOWN) {
+                return false;
+            }
+            return findInterceptingOnItemTouchListener(e);
+        } else {
+            mInterceptingOnItemTouchListener.onTouchEvent(this, e);
+            final int action = e.getAction();
+            if (action == MotionEvent.ACTION_CANCEL || action == MotionEvent.ACTION_UP) {
+                mInterceptingOnItemTouchListener = null;
+            }
+            return true;
+        }
+    }
+
+    private boolean findInterceptingOnItemTouchListener(@NonNull MotionEvent e) {
+        int action = e.getAction();
+        if (mPhantomOnItemTouchListener != null
+                && mPhantomOnItemTouchListener.onInterceptTouchEvent(this, e)
+                && action != MotionEvent.ACTION_CANCEL) {
+            mInterceptingOnItemTouchListener = mPhantomOnItemTouchListener;
+            return true;
+        }
+        return false;
+    }
+
+    private static class RecyclerViewHelper implements FastScroller.ViewHelper {
+
+        @NonNull
+        private final RecyclerView mView;
+
+        @NonNull
+        private final Rect mTempRect = new Rect();
+
+        public RecyclerViewHelper(@NonNull RecyclerView view) {
+            mView = view;
+        }
+
+        @Override
+        public void addOnPreDrawListener(@NonNull Runnable onPreDraw) {
+            mView.addItemDecoration(new RecyclerView.ItemDecoration() {
+                @Override
+                public void onDraw(@NonNull Canvas canvas, @NonNull RecyclerView parent,
+                                   @NonNull RecyclerView.State state) {
+                    onPreDraw.run();
+                }
+            });
+        }
+
+        @Override
+        public void addOnScrollChangedListener(@NonNull Runnable onScrollChanged) {
+            mView.addOnScrollListener(new RecyclerView.OnScrollListener() {
+                @Override
+                public void onScrolled(@NonNull RecyclerView recyclerView, int dx, int dy) {
+                    onScrollChanged.run();
+                }
+            });
+        }
+
+        @Override
+        public void addOnTouchEventListener(@NonNull Predicate<MotionEvent> onTouchEvent) {
+            mView.addOnItemTouchListener(new RecyclerView.SimpleOnItemTouchListener() {
+                @Override
+                public boolean onInterceptTouchEvent(@NonNull RecyclerView recyclerView,
+                                                     @NonNull MotionEvent event) {
+                    return onTouchEvent.test(event);
+                }
+                @Override
+                public void onTouchEvent(@NonNull RecyclerView recyclerView,
+                                         @NonNull MotionEvent event) {
+                    onTouchEvent.test(event);
+                }
+            });
+        }
+
+        @Override
+        public int getScrollRange() {
+            int itemCount = getItemCount();
+            if (itemCount == 0) {
+                return 0;
+            }
+            int itemHeight = getItemHeight();
+            if (itemHeight == 0) {
+                return 0;
+            }
+            return mView.getPaddingTop() + itemCount * itemHeight + mView.getPaddingBottom();
+        }
+
+        @Override
+        public int getScrollOffset() {
+            int firstItemPosition = getFirstItemPosition();
+            if (firstItemPosition == RecyclerView.NO_POSITION) {
+                return 0;
+            }
+            int itemHeight = getItemHeight();
+            int firstItemTop = getFirstItemOffset();
+            return mView.getPaddingTop() + firstItemPosition * itemHeight - firstItemTop;
+        }
+
+        @Override
+        public void scrollTo(int offset) {
+            // Stop any scroll in progress for RecyclerView.
+            mView.stopScroll();
+            offset -= mView.getPaddingTop();
+            int itemHeight = getItemHeight();
+            // firstItemPosition should be non-negative even if paddingTop is greater than item height.
+            int firstItemPosition = Math.max(0, offset / itemHeight);
+            int firstItemTop = firstItemPosition * itemHeight - offset;
+            scrollToPositionWithOffset(firstItemPosition, firstItemTop);
+        }
+
+        @Nullable
+        @Override
+        public String getPopupText() {
+            RecyclerView.Adapter<?> adapter = mView.getAdapter();
+            if (!(adapter instanceof PopupTextProvider)) {
+                return null;
+            }
+            PopupTextProvider popupTextProvider = (PopupTextProvider) adapter;
+            int position = getFirstItemAdapterPosition();
+            if (position == RecyclerView.NO_POSITION) {
+                return null;
+            }
+            return popupTextProvider.getPopupText(position);
+        }
+
+        private int getItemCount() {
+            LinearLayoutManager linearLayoutManager = getVerticalLinearLayoutManager();
+            if (linearLayoutManager == null) {
+                return 0;
+            }
+            int itemCount = linearLayoutManager.getItemCount();
+            if (itemCount == 0) {
+                return 0;
+            }
+            if (linearLayoutManager instanceof GridLayoutManager) {
+                GridLayoutManager gridLayoutManager = (GridLayoutManager) linearLayoutManager;
+                itemCount = (itemCount - 1) / gridLayoutManager.getSpanCount() + 1;
+            }
+            return itemCount;
+        }
+
+        private int getItemHeight() {
+            if (mView.getChildCount() == 0) {
+                return 0;
+            }
+            View itemView = mView.getChildAt(0);
+            mView.getDecoratedBoundsWithMargins(itemView, mTempRect);
+            return mTempRect.height();
+        }
+
+        private int getFirstItemPosition() {
+            int position = getFirstItemAdapterPosition();
+            LinearLayoutManager linearLayoutManager = getVerticalLinearLayoutManager();
+            if (linearLayoutManager == null) {
+                return RecyclerView.NO_POSITION;
+            }
+            if (linearLayoutManager instanceof GridLayoutManager) {
+                GridLayoutManager gridLayoutManager = (GridLayoutManager) linearLayoutManager;
+                position /= gridLayoutManager.getSpanCount();
+            }
+            return position;
+        }
+
+        private int getFirstItemAdapterPosition() {
+            if (mView.getChildCount() == 0) {
+                return RecyclerView.NO_POSITION;
+            }
+            View itemView = mView.getChildAt(0);
+            LinearLayoutManager linearLayoutManager = getVerticalLinearLayoutManager();
+            if (linearLayoutManager == null) {
+                return RecyclerView.NO_POSITION;
+            }
+            return linearLayoutManager.getPosition(itemView);
+        }
+
+        private int getFirstItemOffset() {
+            if (mView.getChildCount() == 0) {
+                return RecyclerView.NO_POSITION;
+            }
+            View itemView = mView.getChildAt(0);
+            mView.getDecoratedBoundsWithMargins(itemView, mTempRect);
+            return mTempRect.top;
+        }
+
+        private void scrollToPositionWithOffset(int position, int offset) {
+            LinearLayoutManager linearLayoutManager = getVerticalLinearLayoutManager();
+            if (linearLayoutManager == null) {
+                return;
+            }
+            if (linearLayoutManager instanceof GridLayoutManager) {
+                GridLayoutManager gridLayoutManager = (GridLayoutManager) linearLayoutManager;
+                position *= gridLayoutManager.getSpanCount();
+            }
+            // LinearLayoutManager actually takes offset from paddingTop instead of top of RecyclerView.
+            offset -= mView.getPaddingTop();
+            linearLayoutManager.scrollToPositionWithOffset(position, offset);
+        }
+
+        @Nullable
+        private LinearLayoutManager getVerticalLinearLayoutManager() {
+            RecyclerView.LayoutManager layoutManager = mView.getLayoutManager();
+            if (!(layoutManager instanceof LinearLayoutManager)) {
+                return null;
+            }
+            LinearLayoutManager linearLayoutManager = (LinearLayoutManager) layoutManager;
+            if (linearLayoutManager.getOrientation() != RecyclerView.VERTICAL) {
+                return null;
+            }
+            return linearLayoutManager;
+        }
+    }
+
+    private class ViewHelper extends RecyclerViewHelper {
+
+        ViewHelper(@NonNull RecyclerView view) {
+            super(view);
+        }
+
+        @Override
+        public void addOnTouchEventListener(@NonNull Predicate<MotionEvent> onTouchEvent) {
+            mPhantomOnItemTouchListener = new RecyclerView.SimpleOnItemTouchListener() {
+                @Override
+                public boolean onInterceptTouchEvent(@NonNull RecyclerView recyclerView,
+                                                     @NonNull MotionEvent event) {
+                    return onTouchEvent.test(event);
+                }
+
+                @Override
+                public void onTouchEvent(@NonNull RecyclerView recyclerView,
+                                         @NonNull MotionEvent event) {
+                    onTouchEvent.test(event);
+                }
+            };
+        }
+    }
+}
diff --git a/app/src/main/java/com/zeapo/pwdstore/PasswordFragment.kt b/app/src/main/java/com/zeapo/pwdstore/PasswordFragment.kt
index c9b9824f..eb97f1b8 100644
--- a/app/src/main/java/com/zeapo/pwdstore/PasswordFragment.kt
+++ b/app/src/main/java/com/zeapo/pwdstore/PasswordFragment.kt
@@ -17,8 +17,8 @@ import androidx.appcompat.view.ActionMode
 import androidx.fragment.app.Fragment
 import androidx.fragment.app.activityViewModels
 import androidx.lifecycle.observe
+import androidx.recyclerview.widget.FixOnItemTouchDispatchRecyclerView
 import androidx.recyclerview.widget.LinearLayoutManager
-import androidx.recyclerview.widget.RecyclerView
 import androidx.swiperefreshlayout.widget.SwipeRefreshLayout
 import com.google.android.material.floatingactionbutton.FloatingActionButton
 import com.google.android.material.snackbar.Snackbar
@@ -35,7 +35,7 @@ import me.zhanghai.android.fastscroll.FastScrollerBuilder
 
 class PasswordFragment : Fragment() {
     private lateinit var recyclerAdapter: PasswordItemRecyclerAdapter
-    private lateinit var recyclerView: RecyclerView
+    private lateinit var recyclerView: FixOnItemTouchDispatchRecyclerView
     private lateinit var listener: OnFragmentInteractionListener
     private lateinit var swipeRefresher: SwipeRefreshLayout
 
@@ -111,9 +111,6 @@ class PasswordFragment : Fragment() {
             adapter = recyclerAdapter
         }
 
-        // FastScrollerBuilder.build() needs to be called *before* recyclerAdapter.makeSelectable(),
-        // as otherwise dragging the fast scroller will lead to items being selected.
-        // See https://github.com/zhanghai/AndroidFastScroll/issues/13
         FastScrollerBuilder(recyclerView).build()
         recyclerAdapter.makeSelectable(recyclerView)
         registerForContextMenu(recyclerView)
diff --git a/app/src/main/res/layout/password_recycler_view.xml b/app/src/main/res/layout/password_recycler_view.xml
index 5368d593..8348bea2 100644
--- a/app/src/main/res/layout/password_recycler_view.xml
+++ b/app/src/main/res/layout/password_recycler_view.xml
@@ -15,7 +15,7 @@
         android:layout_width="match_parent"
         android:layout_height="match_parent">
 
-        <androidx.recyclerview.widget.RecyclerView
+        <androidx.recyclerview.widget.FixOnItemTouchDispatchRecyclerView
             android:id="@+id/pass_recycler"
             android:layout_width="match_parent"
             android:layout_height="match_parent"