/*******************************************************************************
* Copyright 2011-2013 Sergey Tarasevich
*
* 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
*
* 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.nostra13.universalimageloader.core.listener;
import android.widget.AbsListView;
import android.widget.AbsListView.OnScrollListener;
import android.widget.GridView;
import android.widget.ListView;
import com.nostra13.universalimageloader.core.ImageLoader;
/**
* Listener-helper for {@linkplain AbsListView list views} ({@link ListView}, {@link GridView}) which can
* {@linkplain ImageLoader#pause() pause ImageLoader's tasks} while list view is scrolling (touch scrolling and/or
* fling). It prevents redundant loadings.<br />
* Set it to your list view's {@link AbsListView#setOnScrollListener(OnScrollListener) setOnScrollListener(...)}.<br />
* This listener can wrap your custom {@linkplain OnScrollListener listener}.
*
* @author Sergey Tarasevich (nostra13[at]gmail[dot]com)
* @since 1.7.0
*/
public class PauseOnScrollListener implements OnScrollListener {
private ImageLoader imageLoader;
private final boolean pauseOnScroll;
private final boolean pauseOnFling;
private final OnScrollListener externalListener;
/**
* Constructor
*
* @param imageLoader {@linkplain ImageLoader} instance for controlling
* @param pauseOnScroll Whether {@linkplain ImageLoader#pause() pause ImageLoader} during touch scrolling
* @param pauseOnFling Whether {@linkplain ImageLoader#pause() pause ImageLoader} during fling
*/
public PauseOnScrollListener(ImageLoader imageLoader, boolean pauseOnScroll, boolean pauseOnFling) {
this(imageLoader, pauseOnScroll, pauseOnFling, null);
}
/**
* Constructor
*
* @param imageLoader {@linkplain ImageLoader} instance for controlling
* @param pauseOnScroll Whether {@linkplain ImageLoader#pause() pause ImageLoader} during touch scrolling
* @param pauseOnFling Whether {@linkplain ImageLoader#pause() pause ImageLoader} during fling
* @param customListener Your custom {@link OnScrollListener} for {@linkplain AbsListView list view} which also
* will be get scroll events
*/
public PauseOnScrollListener(ImageLoader imageLoader, boolean pauseOnScroll, boolean pauseOnFling,
OnScrollListener customListener) {
this.imageLoader = imageLoader;
this.pauseOnScroll = pauseOnScroll;
this.pauseOnFling = pauseOnFling;
externalListener = customListener;
}
@Override
public void onScrollStateChanged(AbsListView view, int scrollState) {
switch (scrollState) {
case OnScrollListener.SCROLL_STATE_IDLE:
imageLoader.resume();
break;
case OnScrollListener.SCROLL_STATE_TOUCH_SCROLL:
if (pauseOnScroll) {
imageLoader.pause();
}
break;
case OnScrollListener.SCROLL_STATE_FLING:
if (pauseOnFling) {
imageLoader.pause();
}
break;
}
if (externalListener != null) {
externalListener.onScrollStateChanged(view, scrollState);
}
}
@Override
public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
if (externalListener != null) {
externalListener.onScroll(view, firstVisibleItem, visibleItemCount, totalItemCount);
}
}
}