...或者我们实现一个行为类似于 SQliteCursor 的自定义游标,除了它返回 ColumnCount+1 并在查询时为该“虚拟”组附加一个“虚拟”元素...
或者你在适配器级别实现它,欺骗它认为Cursor
基于的有一个额外的行。我写了一个例子(一个简单的场景),但它需要工作:
public class ExtraGroupAdapter extends SimpleCursorTreeAdapter {
private Cursor mExtraChildCursor;
@Override
protected Cursor getChildrenCursor(Cursor groupCursor) {
// if groupCursor.getPosition() returns -1 we have to provide the Cursor for our fake group
}
@Override
public int getGroupCount() {
// 1 more
return super.getGroupCount() + 1;
}
@Override
public View getGroupView(int groupPosition, boolean isExpanded,
View convertView, ViewGroup parent) {
if (groupPosition == 0) {
if (getCursor() == null) {
throw new IllegalStateException(
"this should only be called when the cursor is valid");
}
View v;
if (convertView == null) {
v = newGroupView(mContext, getCursor(), isExpanded, parent);
} else {
v = convertView;
}
// if it's position 0 move the group Cursor to position -1 to
// let the bindGroupView method that is deals with our fake row
getCursor().moveToPosition(-1);
bindGroupView(v, mContext, getCursor(), isExpanded);
return v;
} else {
return super.getGroupView(groupPosition - 1, isExpanded,
convertView, parent);
}
}
@Override
protected void bindGroupView(View view, Context context, Cursor cursor,
boolean isExpanded) {
if (cursor.getPosition() == -1) {
// bind our fake row, unfortunately this must be done manually
} else {
super.bindGroupView(view, context, cursor, isExpanded);
}
}
@Override
public View getChildView(int groupPosition, int childPosition,
boolean isLastChild, View convertView, ViewGroup parent) {
if (groupPosition == 0) {
// replicate what the CursorTreeAdapter does for our fake group
// position 0
if (getCursor() == null) {
throw new IllegalStateException(
"this should only be called when the cursor is valid");
}
View v;
getCursor().moveToPosition(-1);
mExtraChildCursor.moveToPosition(childPosition);
if (convertView == null) {
v = newChildView(mContext, mExtraChildCursor, isLastChild,
parent);
} else {
v = convertView;
}
bindChildView(v, mContext, mExtraChildCursor, isLastChild);
return v;
} else {
// use the default implementation but offset the Cursor's
// current position
return super.getChildView(groupPosition - 1, childPosition,
isLastChild, convertView, parent);
}
}
@Override
public int getChildrenCount(int groupPosition) {
if (groupPosition == 0) {
// implement the trick
if (mExtraChildCursor == null) {
getCursor().moveToPosition(-1); // in the getChildrenCursor
// a Cursor position of -1
// means it is the fake row
mExtraChildCursor = getChildrenCursor(getCursor());
return 0;
} else {
return mExtraChildCursor.getCount();
}
}
return super.getChildrenCount(groupPosition);
}
@Override
public void setChildrenCursor(int groupPosition, Cursor childrenCursor) {
if (groupPosition == 0) {
// hold a reference to the extra Cursor
mExtraChildCursor = childrenCursor;
notifyDataSetChanged();
} else {
super.setChildrenCursor(groupPosition, childrenCursor);
}
}
}
我应该按照为简单场景设计的CursorTreeAdapter
那样进行扩展。SimpleCursorTreeAdapter
我写的是放置在位置 0 的假行(但经过仔细计算,可以使用不同的位置)。