ScrollView滑动监听显示标题栏

重写ScrollView:
package com.example.ningac.mathom_a.myview;

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

/**
* Created by Ning.A.C on 2017/12/17.
*/

public class MyScrollView extends ScrollView{
private ScrollViewListener scrollViewListener = null;

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

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

@Override
protected void onScrollChanged(int x, int y, int oldx, int oldy) {
//x为当前滑动条的横坐标，y表示当前滑动条的纵坐标，oldx为前一次滑动的横坐标，oldy表示前一次滑动的纵坐标
super.onScrollChanged(x, y, oldx, oldy);
if (scrollViewListener != null) {
//在这里将方法暴露出去
scrollViewListener.onScrollChanged(this, x, y, oldx, oldy);
}
}

//是否要其弹性滑动
@Override
protected boolean overScrollBy(int deltaX, int deltaY, int scrollX,
int scrollY, int scrollRangeX, int scrollRangeY,
int maxOverScrollX, int maxOverScrollY, boolean isTouchEvent) {

// 弹性滑动关键则是maxOverScrollX， 以及maxOverScrollY，
// 一般默认值都是0，需要弹性时，更改其值即可
// 即就是，为零则不会发生弹性，不为零（>0,负数未测试）则会滑动到其值的位置
return super.overScrollBy(deltaX, deltaY, scrollX, scrollY, scrollRangeX,
scrollRangeY, 0, 0, isTouchEvent);
}
//接口
public interface ScrollViewListener {

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

}
public void setScrollViewListener(ScrollViewListener listener)
{
scrollViewListener=listener;
}
}

设置标题栏:scrollView.setScrollViewListener(new MyScrollView.ScrollViewListener() {@Overridepublic void onScrollChanged(View scrollView, int x, int y, int oldx, int oldy) {if (isFirst) {isFirst = false;}titleAnim(oldy,y);}});public void titleAnim(int oldy,int y){Log.d("zzz",oldy+"    "+y);if(y==0){found_title.setAlpha(0);}else{if (y <= 100) {float alpha =((float) y) / 100;found_title.setAlpha(alpha);if (alpha==0){found_title.setClickable(false);}else{found_title.setClickable(true);}}else {found_title.setAlpha(1);}}//        }else{////        }//        if (y < 200) {//            float alpha = 1 - ((float) y) / 200;//            found_title.setAlpha(alpha);//            if (alpha==0)//            {//                found_title.setClickable(false);//            }else//            {//                found_title.setClickable(true);//            }//        } else {//            //下滑显示标题栏//            if (oldy > y) {//                found_title.setAlpha(1);//                found_title.setClickable(true);//            } else {//                found_title.setAlpha(0);//                found_title.setClickable(false);//            }//        }}