在业务需求中，有时会遇到需要监听ScrollView实现页面的一些业务效果

主要思路：创建Handler,在ScrollView滑动的时候，先清空所有消息，然后发送延时消息，如果能接收到消息，说明滑动停止，下面是具体实现的代码

public class ObservableScrollView extends NestedScrollView {

  private OnScrollStatusListener onScrollStatusListener;

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

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

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

  @Override protected void onScrollChanged(int l, int t, int oldl, int oldt) {
    super.onScrollChanged(l, t, oldl, oldt);
    if (onScrollStatusListener != null) {
      onScrollStatusListener.onScrolling();
      mHandler.removeCallbacksAndMessages(null);
      mHandler.sendEmptyMessageDelayed(0x01, 200);
    }
  }

  public void setOnScrollStatusListener(OnScrollStatusListener onScrollStatusListener) {
    this.onScrollStatusListener = onScrollStatusListener;
  }

  private Handler mHandler = new Handler() {

    @Override public void handleMessage(Message msg) {
      super.handleMessage(msg);
      switch (msg.what) {
        case 0x01:
          if (onScrollStatusListener != null) {
            onScrollStatusListener.onScrollStop();
          }
          break;
      }
    }
  };

  @Override protected void onDetachedFromWindow() {
    super.onDetachedFromWindow();
    mHandler.removeCallbacksAndMessages(null);
  }

  public interface OnScrollStatusListener {
    void onScrollStop();

    void onScrolling();
  }
}

然后就可以引用自定义的ObservableScrollView了，下面是布局文件

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.yuntu.scrollview.MainActivity"
    >
  <com.yuntu.scrollview.ObservableScrollView
      android:id="@+id/scrollView"
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      >
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical"
        >
      <TextView
          android:layout_width="match_parent"
          android:layout_height="150dp"
          android:background="#FF352E"
          android:gravity="center"
          android:text="测试"
          android:textColor="#3D4552"
          />
      <TextView
          android:layout_width="match_parent"
          android:layout_height="150dp"
          android:background="#FF6738"
          android:gravity="center"
          android:text="测试"
          android:textColor="#3D4552"
          />
      <TextView
          android:layout_width="match_parent"
          android:layout_height="150dp"
          android:background="#FFFFFF"
          android:gravity="center"
          android:text="测试"
          android:textColor="#3D4552"
          />
      <TextView
          android:layout_width="match_parent"
          android:layout_height="150dp"
          android:background="#FF352E"
          android:gravity="center"
          android:text="测试"
          android:textColor="#3D4552"
          />
      <TextView
          android:layout_width="match_parent"
          android:layout_height="150dp"
          android:background="#4E65FE"
          android:gravity="center"
          android:text="测试"
          android:textColor="#3D4552"
          />
      <TextView
          android:layout_width="match_parent"
          android:layout_height="150dp"
          android:background="#FFFFFF"
          android:gravity="center"
          android:text="测试"
          android:textColor="#3D4552"
          />
    </LinearLayout>
  </com.yuntu.scrollview.ObservableScrollView>
  <TextView
      android:id="@+id/tv_test"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:gravity="center"
      android:text="停止滑动"
      android:textColor="#3D4552"
      android:textSize="20sp"
      />

</FrameLayout>

然后在代码中

ObservableScrollView scrollView = findViewById(R.id.scrollView);
    final TextView tvTest = findViewById(R.id.tv_test);
    scrollView.setOnScrollStatusListener(new ObservableScrollView.OnScrollStatusListener() {
      @Override public void onScrollStop() {
        tvTest.setText("停止滑动");
      }

      @Override public void onScrolling() {
        tvTest.setText("滑动中");
      }
    });

可以监听到ScrollView的滑动跟静止状态变化。