Android 监听ScrollView滑动距离简单处理

使用ScrollView时， 有时候我们需要要获取它滑动的距离，Android的API给我们提供了设置监听的方法：

scrollView.setOnScrollChangeListener(new View.OnScrollChangeListener() {
@Override
public void onScrollChange(View v, int scrollX, int scrollY, int oldScrollX, int oldScrollY) {

}
});

很遗憾的是：Call requires API 23

点进去看下View里面的OnScrollChangeListener在哪个方法里面监听位置：

/**
* This is called in response to an internal scroll in this view (i.e., the
* view scrolled its own contents). This is typically as a result of
* {@link #scrollBy(int, int)} or {@link #scrollTo(int, int)} having been
* called.
*
* @param l Current horizontal scroll origin.
* @param t Current vertical scroll origin.
* @param oldl Previous horizontal scroll origin.
* @param oldt Previous vertical scroll origin.
*/
protected void onScrollChanged(int l, int t, int oldl, int oldt) {
notifySubtreeAccessibilityStateChangedIfNeeded();

if (AccessibilityManager.getInstance(mContext).isEnabled()) {
postSendViewScrolledAccessibilityEventCallback();
}

mBackgroundSizeChanged = true;
if (mForegroundInfo != null) {
mForegroundInfo.mBoundsChanged = true;
}

final AttachInfo ai = mAttachInfo;
if (ai != null) {
ai.mViewScrollChanged = true;
}

if (mListenerInfo != null && mListenerInfo.mOnScrollChangeListener != null) {
mListenerInfo.mOnScrollChangeListener.onScrollChange(this, l, t, oldl, oldt);
}
}

一看其实实现不难，不就是自定义个ScrollView, 里面多写个监听， 实现如下：

import android.content.Context;
import android.util.AttributeSet;
import android.widget.ScrollView;

/**
* Created by hucanhui on 16/7/28.
*/
public class ObservableScrollView extends ScrollView{
private OnScollChangedListener onScollChangedListener = null;

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

public ObservableScrollView(Context context, AttributeSet attrs,
int defStyle) {
super(context, attrs, defStyle);
}

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

public void setOnScollChangedListener(OnScollChangedListener onScollChangedListener) {
this.onScollChangedListener = onScollChangedListener;
}

@Override
protected void onScrollChanged(int x, int y, int oldx, int oldy) {
super.onScrollChanged(x, y, oldx, oldy);
if (onScollChangedListener != null) {
onScollChangedListener.onScrollChanged(this, x, y, oldx, oldy);
}
}

public interface OnScollChangedListener {

void onScrollChanged(ObservableScrollView scrollView, int x, int y, int oldx, int oldy);

}
}

使用简单：

scrollView.setOnScollChangedListener(new ObservableScrollView.OnScollChangedListener() {
@Override
public void onScrollChanged(ObservableScrollView scrollView, int x, int y, int oldx, int oldy){
}
});