PullToRefreshScrollView 添加滚动监听

给PullToRefreshScrollView添加滚动监听前，我们需要先知道怎么给ScrollView添加滚动监听。因为ScrollView没有滚动监听事件（setOnScrollChangeListener这个要sdk23不考虑），那只能我们自己来实现。

其实ScrollView有一个对滚动进行监听的方法（onScrollChanged），但是是protected类型的，我们的实现就是围绕这个方法。实现方法很简单，具体代码如下：

public class MyScrollView extends ScrollView {

private OnScrollListener listener;

public MyScrollView(Context context) {
super(context);
}

public MyScrollView(Context context, AttributeSet attrs) {
super(context, attrs);
}

public void setOnScrollListener(OnScrollListener listener) {
this.listener = listener;
}

@Override
protected void onScrollChanged(int l, int t, int oldl, int oldt) {
super.onScrollChanged(l, t, oldl, oldt);
if(listener!=null)
{
listener.onScroll(getScrollY());
}
}
public interface OnScrollListener {
void onScroll(int y);
}
}

这样就实现了对ScrollView的滚动监听，好了，回到重点，怎么去实现PullToRefreshScrollView的滚动监听，还是围绕上面的方法来的，在PullToRefresh库中添加两个类，一个是我们上面写的，另一个将PullToRefreshScrollView中的代码复制一遍，然后将里面所有的ScrollView改为MyScrollView（你自定义的有滚动监听ScrollView类名）就行了。



其中PullToRefreshScrollView2的代码如下：

/*******************************************************************************
* Copyright 2011, 2012 Chris Banes.
*
* 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.handmark.pulltorefresh.library;

import android.annotation.TargetApi;
import android.content.Context;
import android.os.Build.VERSION;
import android.os.Build.VERSION_CODES;
import android.util.AttributeSet;
import android.util.Log;
import android.view.View;
import android.widget.ScrollView;

public class PullToRefreshScrollView2 extends PullToRefreshBase<MyScrollView> {

public PullToRefreshScrollView2(Context context) {
super(context);
}

public PullToRefreshScrollView2(Context context, AttributeSet attrs) {
super(context, attrs);
}

public PullToRefreshScrollView2(Context context, Mode mode) {
super(context, mode);
}

public PullToRefreshScrollView2(Context context, Mode mode, AnimationStyle style) {
super(context, mode, style);
}

@Override
public final Orientation getPullToRefreshScrollDirection() {
return Orientation.VERTICAL;
}

@Override
protected MyScrollView createRefreshableView(Context context, AttributeSet attrs) {
MyScrollView scrollView;
if (VERSION.SDK_INT >= VERSION_CODES.GINGERBREAD) {
scrollView = new InternalScrollViewSDK9(context, attrs);
} else {
scrollView = new MyScrollView(context, attrs);
}

scrollView.setId(R.id.scrollview);
return scrollView;
}

@Override
protected boolean isReadyForPullStart() {
return mRefreshableView.getScrollY() == 0;
}

@Override
protected boolean isReadyForPullEnd() {
View scrollViewChild = mRefreshableView.getChildAt(0);
if (null != scrollViewChild) {
return mRefreshableView.getScrollY() >= (scrollViewChild.getHeight() - getHeight());
}
return false;
}

@TargetApi(9)
final class InternalScrollViewSDK9 extends MyScrollView {

public InternalScrollViewSDK9(Context context, AttributeSet attrs) {
super(context, attrs);
}

@Override
protected boolean overScrollBy(int deltaX, int deltaY, int scrollX, int scrollY, int scrollRangeX,
int scrollRangeY, int maxOverScrollX, int maxOverScrollY, boolean isTouchEvent) {

final boolean returnValue = super.overScrollBy(deltaX, deltaY, scrollX, scrollY, scrollRangeX,
scrollRangeY, maxOverScrollX, maxOverScrollY, isTouchEvent);

// Does all of the hard work...
OverscrollHelper.overScrollBy(PullToRefreshScrollView2.this, deltaX, scrollX, deltaY, scrollY,
getScrollRange(), isTouchEvent);

return returnValue;
}

/**
* Taken from the AOSP ScrollView source
*/
private int getScrollRange() {
int scrollRange = 0;
if (getChildCount() > 0) {
View child = getChildAt(0);
scrollRange = Math.max(0, child.getHeight() - (getHeight() - getPaddingBottom() - getPaddingTop()));
}
return scrollRange;
}
}
}

好了， 监听已经写完了，下面是使用代码：

ptrsv2.getRefreshableView().setOnScrollListener(new com.handmark.pulltorefresh.library.MyScrollView.OnScrollListener() {
@Override
public void onScroll(int y) {

ToastUtil.toastShort("滚动中.."+y);

}});