android/sdk/src/main/java/com/taobao/weex/ui/view/listview/ExtendedLinearLayoutManager.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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
 * 
 *   http://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 com.taobao.weex.ui.view.listview;

import android.content.Context;
import android.graphics.PointF;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.LinearSmoothScroller;
import android.support.v7.widget.RecyclerView;

/**
 * Created by moxun on 17/2/16.
 */

public class ExtendedLinearLayoutManager extends LinearLayoutManager{

    private RecyclerView.SmoothScroller smoothScroller;


    private OnSmoothScrollEndListener onScrollEndListener;

    public ExtendedLinearLayoutManager(Context context) {
        super(context, VERTICAL, false);
    }

    public ExtendedLinearLayoutManager(Context context, int orientation, boolean reverseLayout) {
        super(context, orientation, reverseLayout);
    }

    @Override
    public boolean supportsPredictiveItemAnimations() {
        return false;
    }

    public void onLayoutChildren(RecyclerView.Recycler recycler, RecyclerView.State state) {
        try {
            super.onLayoutChildren(recycler, state);
        } catch (IndexOutOfBoundsException e) {
            e.printStackTrace();

        }
    }

    @Override
    public int scrollVerticallyBy(int dy, RecyclerView.Recycler recycler, RecyclerView.State state) {
        try {
            return super.scrollVerticallyBy(dy, recycler, state);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return 0;
    }


    @Override
    public void smoothScrollToPosition(RecyclerView recyclerView, RecyclerView.State state,
                                       int position) {
        if (smoothScroller == null) {
            smoothScroller = new ExtendedLinearLayoutManager.TopSnappedSmoothScroller(recyclerView.getContext());
        }
        smoothScroller.setTargetPosition(position);
        startSmoothScroll(smoothScroller);
    }

    private class TopSnappedSmoothScroller extends LinearSmoothScroller {
        public TopSnappedSmoothScroller(Context context) {
            super(context);

        }

        @Override
        public PointF computeScrollVectorForPosition(int targetPosition) {
            return ExtendedLinearLayoutManager.this
                    .computeScrollVectorForPosition(targetPosition);
        }

        @Override
        protected int getVerticalSnapPreference() {
            return SNAP_TO_START;
        }

        @Override
        protected void onStop() {
            super.onStop();
            if(onScrollEndListener != null){
                onScrollEndListener.onStop();
                onScrollEndListener = null;
            }
        }
    }

    public void setOnScrollEndListener(OnSmoothScrollEndListener onScrollEndListener) {
        this.onScrollEndListener = onScrollEndListener;
    }

    public interface OnSmoothScrollEndListener {
        void  onStop();
    }
}