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
