Android--ExpandbleView源码学习----ExpandableListPosition类

Class OverView

ExpandbaleListPosition类可以指向group的位置或则child的位置。可通过obtainChildPosition(int,int)和obtainGroupPosition(int)获得实例

/**

*根据type返回groupPosition或则childPosition的格式为64位的数据

**/

long getPackedPosition() {
        if (type == CHILD) return ExpandableListView.getPackedPositionForChild(groupPos, childPos);
        else return ExpandableListView.getPackedPositionForGroup(groupPos);
    }

//

static ExpandableListPosition obtain(int type, int groupPos, int childPos, int flatListPos) {
        ExpandableListPosition elp = getRecycledOrCreate(); 
        elp.type = type;
        elp.groupPos = groupPos;
        elp.childPos = childPos;
        elp.flatListPos = flatListPos;
        return elp;
    }

//初始化对象

private void resetState() {
        groupPos = 0;
        childPos = 0;
        flatListPos = 0;
        type = 0;
    }

//返回一个ExpandableListPosition，如果池中有对象则返回池中对象并且移除该对象（将被初始化），如果没有则新new一个对象返回  

 private static ExpandableListPosition getRecycledOrCreate() {
        ExpandableListPosition elp;
        synchronized (sPool) {
            if (sPool.size() > 0) {
                elp = sPool.remove(0);
            } else {
                return new ExpandableListPosition();
            }
        }
        elp.resetState();
        return elp;
    }

//增加一个ExpandableListPosition对象到池中

public void recycle() {
        synchronized (sPool) {
            if (sPool.size() < MAX_POOL_SIZE) {
                sPool.add(this);
            }
        }
    }

//获得一个ExpandableListPosition对象

static ExpandableListPosition obtain(int type, int groupPos, int childPos, int flatListPos) {
    ExpandableListPosition elp = getRecycledOrCreate();
    elp.type = type;
    elp.groupPos = groupPos;
    elp.childPos = childPos;
    elp.flatListPos = flatListPos;
    return elp;
  }

//获得一个group类型的ExpandableListPosition对象

static ExpandableListPosition obtainGroupPosition(int groupPosition) {
        return obtain(GROUP, groupPosition, 0, 0);
    }
 

//获得一个child类型的ExpandableListPosition对象   
 static ExpandableListPosition obtainChildPosition(int groupPosition, int childPosition) { return obtain(CHILD, groupPosition, childPosition, 0); }

//根据位置的封装数据得到位置的ExpandbaleListPostion static ExpandableListPosition obtainPosition(long packedPosition) { if (packedPosition == ExpandableListView.PACKED_POSITION_VALUE_NULL) { return null; } ExpandableListPosition elp = getRecycledOrCreate(); elp.groupPos = ExpandableListView.getPackedPositionGroup(packedPosition); if (ExpandableListView.getPackedPositionType(packedPosition) == ExpandableListView.PACKED_POSITION_TYPE_CHILD) { elp.type = CHILD; elp.childPos = ExpandableListView.getPackedPositionChild(packedPosition); } else { elp.type = GROUP; } return elp; }