listview获取Y轴的滚动距离

最近项目中有个需求，就是根据listview滚动的Y值坐标，要做一个简单的动画效果，可是发现listview.getScrollY()获得到的始终是0，脑袋里一万只草泥马奔腾而过。所以果断的去百度，结果搜到的全是类似这样的结果：
http://www.jcodecraeer.com/a/anzhuokaifa/androidkaifa/2014/0924/1711.html

这样方案，只是比较适合 每个item高度固定的情况，可是我的listview中有是混排的，而且item的高度很有可能不一样，所以结果是不行的。

绞尽脑汁，最后想到了解决方案，解决了问题，方法有点儿low，希望各位给出点儿建议。

废话少说，直接上代码：

自定义listview，监听listview的onscroll事件，在滚动的时候，记录每一个item的高度，最后加起来，就是getScrollY()

 package com.example.luwenxiang.testapplication.widget;

import android.content.Context;
import android.os.Build;
import android.support.annotation.RequiresApi;
import android.util.AttributeSet;
import android.util.Log;
import android.widget.AbsListView;
import android.widget.ListView;

import java.util.ArrayList;

/**
 * Created by luwenxiang on 17-8-10.
 */

public class AcquiredScrollYListview extends ListView implements AbsListView.OnScrollListener {
    private static final String TAG = "AcquiredScrollYListview";
    private OnScrollListener mScrollListener;

    /**
     * 保存上次的firstvisibleposition
     */
    private int mLastFirstVisiblePosition = INVALID_POSITION;

    /**
     * 保存上次的lastvisibleposition
     */
    private int mLastLastVisiblePosition = INVALID_POSITION;
    private ArrayList mLocalHeightList;
    private int mTotalItemCount;

    public AcquiredScrollYListview(Context context) {
        super(context);
        init(context);
    }

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

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

    @RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)
    public AcquiredScrollYListview(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
        super(context, attrs, defStyleAttr, defStyleRes);
        init(context);
    }

    private void init(Context context) {
        super.setOnScrollListener(this);
    }


    @Override
    public void setOnScrollListener(OnScrollListener listener) {
        if (listener == null) return;
        this.mScrollListener = listener;
        super.setOnScrollListener(this);
    }

    @Override
    public void onScrollStateChanged(AbsListView view, int scrollState) {
        if (mScrollListener != null) {
            mScrollListener.onScrollStateChanged(view, scrollState);
        }
    }

    @Override
    public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
        mTotalItemCount = totalItemCount;
        if (mScrollListener != null) {
            mScrollListener.onScroll(view, firstVisibleItem, visibleItemCount, totalItemCount);
        }
    }


    /**
     * 滚动时 实时更新 保存 滚动的y值
     */
    public int getListViewScrollY() {

        if (getChildCount() == 0) {
            Log.i(TAG, "listview's length is zero");
            return -1;
        }

        ArrayList<IntegerValue> localHeight = getHeightList();
        ensureListCapacity(localHeight, Math.max(getLastVisiblePosition(), mTotalItemCount), IntegerValue.class);
        int tempHeight = 0;
        if (mLastFirstVisiblePosition != getFirstVisiblePosition()
                || mLastLastVisiblePosition != getLastVisiblePosition()) {//当 firstvisibleitem 或者 lastvisibleitem 变化的时候都会更新这个值
            mLastFirstVisiblePosition = getFirstVisiblePosition();
            mLastLastVisiblePosition = getLastVisiblePosition();

            for (int i = getFirstVisiblePosition(); i <= getLastVisiblePosition(); i++) {
                int childMeasuredHeight = getChildAt(i - getFirstVisiblePosition()).getMeasuredHeight();
                int savedItemHeight = localHeight.get(i).getValue();
                if (savedItemHeight != childMeasuredHeight) {
                    localHeight.get(i).setValue(childMeasuredHeight);
                    localHeight.get(i).setIndex(i);
                }
            }

            //remove dirty data
            for (int i = getLastVisiblePosition() + 1; i < localHeight.size(); i++) {
                localHeight.get(i).setValue(0);
            }
        }
        for (int i = 0; i < getFirstVisiblePosition(); i++) {
            tempHeight += getHeightList().get(i).getValue();
        }
        tempHeight -= getChildAt(0).getTop();

        return tempHeight;
    }

    private <T> void ensureListCapacity(ArrayList<T> localHeight, int index, Class<T> clazz) {
        if (localHeight == null) return;
        int listSize = localHeight.size();
        if (index < listSize) return;
        localHeight.ensureCapacity(index + 1);

        for (int i = listSize; i <= index; i++) {
            try {
                localHeight.add(clazz.newInstance());
            } catch (InstantiationException e) {
                e.printStackTrace();
            } catch (IllegalAccessException e) {
                e.printStackTrace();
            }
        }
    }


    public ArrayList<IntegerValue> getHeightList() {
        if (mLocalHeightList == null) {
            mLocalHeightList = new ArrayList<IntegerValue>();
        }
        return mLocalHeightList;
    }


    public static class IntegerValue {
        private int index;
        private int value;

        public IntegerValue() {
        }

        public IntegerValue(int index, int value) {
            this.index = index;
            this.value = value;
        }

        public int getIndex() {
            return index;
        }

        public void setIndex(int index) {
            this.index = index;
        }

        public int getValue() {
            return value;
        }

        public void setValue(int value) {
            this.value = value;
        }
    }
}

在activity中测试获取的 值是否准确：

package com.example.luwenxiang.testapplication;

import android.app.Activity;
import android.content.Context;
import android.graphics.Color;
import android.os.Bundle;
import android.util.Log;
import android.view.Gravity;
import android.view.View;
import android.view.ViewGroup;
import android.view.WindowManager;
import android.widget.AbsListView;
import android.widget.BaseAdapter;
import android.widget.ListView;
import android.widget.TextView;

import com.example.luwenxiang.testapplication.widget.AcquiredScrollYListview;

public class MainActivity3 extends Activity {

    private TextView tv_button;
    private AcquiredScrollYListview  listview;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main3);
        initViews();
        setAdapter();
        setScrollListener();
    }

    private void setScrollListener() {
        listview.setOnScrollListener(new AbsListView.OnScrollListener() {
            @Override
            public void onScrollStateChanged(AbsListView view, int scrollState) {

            }

            @Override
            public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
                Log.i("lwx","firstVisibleItem:"+firstVisibleItem+ "||visibleItemCount:"+visibleItemCount+"|| totalItemCount:"+totalItemCount+"|| getListviewScrollY:"+listview.getListViewScrollY());
            }
        });
    }

    private void setAdapter() {
        TextView headerTextView = new TextView(getApplicationContext());
        headerTextView.setText("this is header");
        headerTextView.setHeight(1000);
        headerTextView.setTextColor(Color.parseColor("#000000"));
        listview.addHeaderView(headerTextView);

//        TextView headerTextView1 = new TextView(getApplicationContext());
//        headerTextView1.setText("this is header two");
//        headerTextView1.setHeight(0);
//        headerTextView1.setTextColor(Color.parseColor("#000000"));
//        listview.addHeaderView(headerTextView1);

        listview.setAdapter(new BaseAdapter() {
            @Override
            public int getCount() {
                return 100;
            }

            @Override
            public Object getItem(int position) {
                return null;
            }

            @Override
            public long getItemId(int position) {
                return 0;
            }

            @Override
            public View getView(int position, View convertView, ViewGroup parent) {
                TextView tempView = new TextView(getApplicationContext());
                tempView.setText("item:" + position);
                tempView.setTextColor(Color.parseColor("#000000"));
                tempView.setHeight(500);
                return tempView;
            }
        });
    }

    private void initViews() {
        listview = (AcquiredScrollYListview ) findViewById(R.id.listview);
    }

}

简单记录一下自己的学习心得，也算是 对自己的一种督促