我有一个保存数据的数组,这些数据将在TVirtualStringTree上表示。这个数组是线程安全的,并且是可锁的。并由另一个线程生长。
我的问题是,当VST执行OnMeasureItem事件来测量节点的高度时,当使用OnGetText事件打印数据时,用于测量的数据可能会发生变化。
我已经检查了事件的执行顺序,这对我的设计不好。首先,它为所有未初始化的节点触发OnMeasureItem事件,然后开始调用OnGetText事件。我的意思是,假设我们有3个节点,事件将按此顺序触发:
OnMeasureItem for node 1
OnMeasureItem for node 2
OnMeasureItem for node 3
OnGetText for node 1
OnGetText for node 2
OnGetText for node 3
但我需要这样的东西,这样我才能锁定:
OnMeasureItem for node 1
OnGetText for node 1
OnMeasureItem for node 2
OnGetText for node 2
OnMeasureItem for node 3
OnGetText for node 3
维护在OnMeasureItem和OnGetText事件之间获取的数据同步的最佳方法是什么?
我不想在所有OnMeasureItem()和OnGetText()事件期间锁定我的数组。
谢谢。
新增onTimer:
procedure TMainForm.SyncHexLog;
begin
HexLog.BeginUpdate;
Try
if (HexLog.RootNodeCount <> FirpList.ComOperationCountLagged) then
begin
HexLog.RootNodeCount := FirpList.ComOperationCountLagged;
// measure for fast scrolling
HexLog.ReInitNode(HexLog.GetLastNoInit(), True);
if FAutoScroll then
begin
HexLog.ScrollIntoView(HexLog.GetLast, False, False);
end;
end;
Finally
HexLog.EndUpdate;
End;
end;
发布于 2012-04-15 18:16:10
我会尝试通过随后调用MeasureItemHeight
方法从节点的状态中删除vsHeightMeasured
来手动强制项目测量。它将再次触发OnMeasureItem
。这里的问题再次出现,因为您不应该测量项目超过一次节点的文本更改,但仍然必须处理OnMeasureItem
,因为滚动的东西。
因此,正如您在注释中提到的,您可以将自己的NodeMeasured
标志包含到数据结构中,并在节点的文本发生更改时(当日志项中的某些数据发生更改时)重置它,并在您传递带有强制节点高度测量的OnGetText
事件后设置它。下面是一个伪代码:
procedure TForm1.VirtualStringTreeGetText(Sender: TBaseVirtualTree;
Node: PVirtualNode; Column: TColumnIndex; TextType: TVSTTextType;
var CellText: string);
begin
ThreadList.LockList;
try
// check if the own flag which indicates that the text is new, that
// the data has changed since the last time you were here in OnGetText
// is False and if so, force the node measurement to set current node
// height and set this flag to True to remember we already did this
if not ThreadList.Items[Node.Index].NodeMeasured then
begin
// fake the node measurement, remove the measured flag
Exclude(Node.States, vsHeightMeasured);
// this will trigger the OnMeasureItem again because of removed
// vsHeightMeasured flag from the node's state
VirtualStringTree.MeasureItemHeight(VirtualStringTree.Canvas, Node);
// set the NodeMeasured flag to remember we've measured the item
ThreadList.Items[Node.Index].NodeMeasured := True;
end;
// here set the node's text and unlock your thread safe list
CellText := ThreadList[Node.Index].SomeText;
finally
ThreadList.UnlockList;
end;
end;
if LogHasChanged then
begin
ThreadList.LockList;
try
ThreadList.Items[X].NodeMeasured := False;
ThreadList.Items[X].SomeText := 'Something new';
finally
ThreadList.UnlockList;
end;
end;
https://stackoverflow.com/questions/10160396
复制相似问题