(原创)RecyclerView结合xUtils2.6实现滚动时不加载item,xUtils2.6的源码分析与改造

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我们知道xUtils中的bitmapUtils与listview相配合可以实现滚动时暂停加载

只需要一句话:

listview.addOnScrollListener(new PauseOnScrollListener(
bitmapUtils, false, true));

然而在我所使用的xUtils2.6版本上,如果想对recyclerView使用相似的方法是行不通的

(ps:因为xUtils3只支持api14,所以我没用xUtils3)

recyclerView.addOnScrollListener(new PauseOnScrollListener(
bitmapUtils, false, true));

因为参数需要的是RecyclerView.OnScrollListener,

而xUtils只提供了实现AbsListView.OnScrollListener的listener

这个时候只能自己动手改动xUtils源码了

进入到PauseOnScrollListener的源码中

import android.widget.AbsListView;
import android.widget.AbsListView.OnScrollListener;
import com.lidroid.xutils.BitmapUtils;
import com.lidroid.xutils.task.TaskHandler;public class PauseOnScrollListener implements OnScrollListener { private TaskHandler taskHandler; private final boolean pauseOnScroll;
private final boolean pauseOnFling;
private final OnScrollListener externalListener; /**
* Constructor
*
* @param taskHandler {@linkplain BitmapUtils} instance for controlling
* @param pauseOnScroll Whether {@linkplain BitmapUtils#pause() pause loading} during touch scrolling
* @param pauseOnFling Whether {@linkplain BitmapUtils#pause() pause loading} during fling
*/
public PauseOnScrollListener(TaskHandler taskHandler, boolean pauseOnScroll, boolean pauseOnFling) {
this(taskHandler, pauseOnScroll, pauseOnFling, null);
} /**
* Constructor
*
* @param taskHandler {@linkplain BitmapUtils} instance for controlling
* @param pauseOnScroll Whether {@linkplain BitmapUtils#pause() pause loading} during touch scrolling
* @param pauseOnFling Whether {@linkplain BitmapUtils#pause() pause loading} during fling
* @param customListener Your custom {@link android.widget.AbsListView.OnScrollListener} for {@linkplain android.widget.AbsListView list view} which also will
* be get scroll events
*/
public PauseOnScrollListener(TaskHandler taskHandler, boolean pauseOnScroll, boolean pauseOnFling, OnScrollListener customListener) {
this.taskHandler = taskHandler;
this.pauseOnScroll = pauseOnScroll;
this.pauseOnFling = pauseOnFling;
externalListener = customListener;
} @Override
public void onScrollStateChanged(AbsListView view, int scrollState) {
switch (scrollState) {
case OnScrollListener.SCROLL_STATE_IDLE:
taskHandler.resume();
break;
case OnScrollListener.SCROLL_STATE_TOUCH_SCROLL:
if (pauseOnScroll) {
taskHandler.pause();
}
break;
case OnScrollListener.SCROLL_STATE_FLING:
if (pauseOnFling) {
taskHandler.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);
}
}
}

意外地发现不是很长,其中主要起作用的除了两个重写的方法外,就是TaskHandler这个接口了

BitmapUtils其实是继承了TaskHandler

TaskHandler对handler进行了进一步的封装,方便控制异步任务

TaskHandler具有pause()和resume()两个很重要的方法,由BitmapUtils等实现

@Override
public void pause() {
pauseTask = true;
flushCache();
} @Override
public void resume() {
pauseTask = false;
synchronized (pauseTaskLock) {
pauseTaskLock.notifyAll();
}
}

看到这里思路就比较明显了,我们继承RecyclerView.OnScrollListener并重写其中的回调方法

在回调方法中调用TaskHandler的api,即可达到想要的效果.

精简后的代码如下

import com.lidroid.xutils.BitmapUtils;
import com.lidroid.xutils.task.TaskHandler;import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.RecyclerView.OnScrollListener;;public class PauseOnScrollListener extends RecyclerView.OnScrollListener {
private TaskHandler taskHandler; private boolean pauseOnScroll;
private boolean pauseOnFling;
private OnScrollListener externalListener; /**
* Constructor
*
* @param taskHandler
* {@linkplain BitmapUtils} instance for controlling
* @param pauseOnScroll
* Whether {@linkplain BitmapUtils#pause() pause loading} during
* touch scrolling
* @param pauseOnFling
* Whether {@linkplain BitmapUtils#pause() pause loading} during
* fling
*/
public PauseOnScrollListener(TaskHandler taskHandler,
boolean pauseOnScroll, boolean pauseOnFling) {
this(taskHandler, pauseOnScroll, pauseOnFling, null);
} /**
* Constructor
*
* @param taskHandler
* {@linkplain BitmapUtils} instance for controlling
* @param pauseOnScroll
* Whether {@linkplain BitmapUtils#pause() pause loading} during
* touch scrolling
* @param pauseOnFling
* Whether {@linkplain BitmapUtils#pause() pause loading} during
* fling
* @param customListener
* Your custom
* {@link android.widget.AbsListView.OnScrollListener} for
* {@linkplain android.widget.AbsListView list view} which also
* will be get scroll events
*/
public MyPauseOnScrollListener(TaskHandler taskHandler,
boolean pauseOnScroll, boolean pauseOnFling,
OnScrollListener customListener) {
this.taskHandler = taskHandler;
this.pauseOnScroll = pauseOnScroll;
this.pauseOnFling = pauseOnFling;
externalListener = customListener;
} @Override
public void onScrollStateChanged(RecyclerView view, int newState) {
switch (newState) { case 0:
taskHandler.resume();
break; case 1:
if (pauseOnScroll) {
taskHandler.pause();
}
break; case 2:
if (pauseOnFling) {
taskHandler.pause();
}
break;
}
if (externalListener != null) {
externalListener.onScrollStateChanged(view, scrollState);
}
} @Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
if (externalListener != null) {
externalListener.onScrolled(recyclerView, dx, dy);
}
}}