[Feature] Add FixOnItemTouchListenerRecyclerView.

Author: zhanghai

library/src/main/java/me/zhanghai/android/fastscroll/FixOnItemTouchListenerRecyclerView.java

@@ -0,0 +1,140 @@
+/*
+ * 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 me.zhanghai.android.fastscroll;
+
+import android.content.Context;
+import android.util.AttributeSet;
+import android.view.MotionEvent;
+
+import java.util.ArrayList;
+import java.util.LinkedHashSet;
+import java.util.List;
+import java.util.Set;
+
+import androidx.annotation.AttrRes;
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+import androidx.recyclerview.widget.RecyclerView;
+
+public class FixOnItemTouchListenerRecyclerView extends RecyclerView {
+
+    @NonNull
+    private final OnItemTouchDispatcher mOnItemTouchDispatcher = new OnItemTouchDispatcher();
+
+    public FixOnItemTouchListenerRecyclerView(@NonNull Context context) {
+        super(context);
+
+        init();
+    }
+
+    public FixOnItemTouchListenerRecyclerView(@NonNull Context context,
+                                              @Nullable AttributeSet attrs) {
+        super(context, attrs);
+
+        init();
+    }
+
+    public FixOnItemTouchListenerRecyclerView(@NonNull Context context,
+                                              @Nullable AttributeSet attrs,
+                                              @AttrRes int defStyleAttr) {
+        super(context, attrs, defStyleAttr);
+
+        init();
+    }
+
+    private void init() {
+        super.addOnItemTouchListener(mOnItemTouchDispatcher);
+    }
+
+    @Override
+    public void addOnItemTouchListener(@NonNull OnItemTouchListener listener) {
+        mOnItemTouchDispatcher.addListener(listener);
+    }
+
+    @Override
+    public void removeOnItemTouchListener(@NonNull OnItemTouchListener listener) {
+        mOnItemTouchDispatcher.removeListener(listener);
+    }
+
+    private static class OnItemTouchDispatcher implements OnItemTouchListener {
+
+        @NonNull
+        private final List<OnItemTouchListener> mListeners = new ArrayList<>();
+
+        @NonNull
+        private final Set<OnItemTouchListener> mTrackingListeners = new LinkedHashSet<>();
+
+        @Nullable
+        private OnItemTouchListener mInterceptingListener;
+
+        public void addListener(@NonNull OnItemTouchListener listener) {
+            mListeners.add(listener);
+        }
+
+        public void removeListener(@NonNull OnItemTouchListener listener) {
+            mListeners.remove(listener);
+            mTrackingListeners.remove(listener);
+            if (mInterceptingListener == listener) {
+                mInterceptingListener = null;
+            }
+        }
+
+        // @see RecyclerView#findInterceptingOnItemTouchListener
+        @Override
+        public boolean onInterceptTouchEvent(@NonNull RecyclerView recyclerView,
+                                             @NonNull MotionEvent event) {
+            int action = event.getAction();
+            for (OnItemTouchListener listener : mListeners) {
+                boolean intercepted = listener.onInterceptTouchEvent(recyclerView, event);
+                if (action == MotionEvent.ACTION_CANCEL) {
+                    mTrackingListeners.remove(listener);
+                    continue;
+                }
+                if (intercepted) {
+                    mInterceptingListener = listener;
+                    mTrackingListeners.remove(listener);
+                    event.setAction(MotionEvent.ACTION_CANCEL);
+                    for (OnItemTouchListener trackingListener : mTrackingListeners) {
+                        trackingListener.onInterceptTouchEvent(recyclerView, event);
+                    }
+                    event.setAction(action);
+                    mTrackingListeners.clear();
+                    return true;
+                } else {
+                    mTrackingListeners.add(listener);
+                }
+            }
+            return false;
+        }
+
+        @Override
+        public void onTouchEvent(@NonNull RecyclerView recyclerView, @NonNull MotionEvent event) {
+            mInterceptingListener.onTouchEvent(recyclerView, event);
+            int action = event.getAction();
+            if (action == MotionEvent.ACTION_CANCEL || action == MotionEvent.ACTION_UP) {
+                mInterceptingListener = null;
+            }
+        }
+
+        @Override
+        public void onRequestDisallowInterceptTouchEvent(boolean disallowIntercept) {
+            for (OnItemTouchListener listener : mListeners) {
+                listener.onRequestDisallowInterceptTouchEvent(disallowIntercept);
+            }
+        }
+    }
+}