<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<ExpandableListView
android:id="@+id/expandableListView"
android:layout_width="match_parent"
android:layout_height="match_parent" >
</ExpandableListView>
<FrameLayout
android:id="@+id/topGroup"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical" >
</FrameLayout>
</FrameLayout>

/**
* here is very importance for indicator group
*/
public void onScroll(AbsListView view, int firstVisibleItem,
int visibleItemCount, int totalItemCount) {
final ExpandableListView listView = (ExpandableListView) view;
/**
* calculate point (0,0)
*/
int npos = view.pointToPosition(0, 0);// 其實(shí)就是firstVisibleItem
if (npos == AdapterView.INVALID_POSITION)// 如果第一個(gè)位置值無(wú)效
return;
long pos = listView.getExpandableListPosition(npos);
int childPos = ExpandableListView.getPackedPositionChild(pos);// 獲取第一行child的id
int groupPos = ExpandableListView.getPackedPositionGroup(pos);// 獲取第一行g(shù)roup的id
if (childPos == AdapterView.INVALID_POSITION) {// 第一行不是顯示child,就是group,此時(shí)沒必要顯示指示器
View groupView = listView.getChildAt(npos
- listView.getFirstVisiblePosition());// 第一行的view
indicatorGroupHeight = groupView.getHeight();// 獲取group的高度
indicatorGroup.setVisibility(View.GONE);// 隱藏指示器
} else {
indicatorGroup.setVisibility(View.VISIBLE);// 滾動(dòng)到第一行是child，就顯示指示器
}
// get an error data, so return now
if (indicatorGroupHeight == 0) {
return;
}
// update the data of indicator group view
if (groupPos != indicatorGroupId) {// 如果指示器顯示的不是當(dāng)前group
mAdapter.getGroupView(groupPos, listView.isGroupExpanded(groupPos),
indicatorGroup.getChildAt(0), null);// 將指示器更新為當(dāng)前group
indicatorGroupId = groupPos;
Log.e(TAG, PRE + "bind to new group,group position = " + groupPos);
// mAdapter.hideGroup(indicatorGroupId); // we set this group view
// to be hided
// 為此指示器增加點(diǎn)擊事件
indicatorGroup.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
// TODO Auto-generated method stub
listView.collapseGroup(indicatorGroupId);
}
});
}
if (indicatorGroupId == -1) // 如果此時(shí)grop的id無(wú)效，則返回
return;
/**
* calculate point (0,indicatorGroupHeight) 下面是形成往上推出的效果
*/
int showHeight = indicatorGroupHeight;
int nEndPos = listView.pointToPosition(0, indicatorGroupHeight);// 第二個(gè)item的位置
if (nEndPos == AdapterView.INVALID_POSITION)// 如果無(wú)效直接返回
return;
long pos2 = listView.getExpandableListPosition(nEndPos);
int groupPos2 = ExpandableListView.getPackedPositionGroup(pos2);// 獲取第二個(gè)group的id
if (groupPos2 != indicatorGroupId) {// 如果不等于指示器當(dāng)前的group
View viewNext = listView.getChildAt(nEndPos
- listView.getFirstVisiblePosition());
showHeight = viewNext.getTop();
Log.e(TAG, PRE + "update the show part height of indicator group:"
+ showHeight);
}
// update group position
MarginLayoutParams layoutParams = (MarginLayoutParams) indicatorGroup
.getLayoutParams();
layoutParams.topMargin = -(indicatorGroupHeight - showHeight);
indicatorGroup.setLayoutParams(layoutParams);
}