指标不旋转 - 加载列表视图

Question

我是TAniindicator组件的新手，因此出于测试目的，我整理了一个项目，该项目将构建列表视图并在构建列表视图时显示/旋转Aniindicator。

type
TLoadThread = class(TThread)
public
constructor Create; reintroduce;
protected
procedure Process;
procedure Execute; override;
end;    
constructor TLoadThread.Create;
begin
inherited Create(True);
FreeOnTerminate := True;
end;
procedure TLoadThread.Process;
begin
Form1.BuildListView;
end;
procedure TLoadThread.Execute;
begin
inherited;
FreeOnTerminate := True;
Synchronize(Process);
end;
var _loadThread : TLoadThread;
procedure TForm1.ThreadTerminated(Sender: TObject);
begin  
AniIndicator1.Enabled := False;
AniIndicator1.Visible := False;
end;
procedure TForm1.BuildListView;
var i : integer;
LI : TListViewItem;
begin
Listview1.BeginUpdate;
try
for i := 1 to 2000 do
begin
LI := Listview1.Items.Add;
LI.Text := 'Listview Item ' + IntToStr(i);
end;
finally
Listview1.EndUpdate;
end;
end;
procedure TForm1.FormCreate(Sender: TObject);
begin
AniIndicator1.Visible := False;
_loadThread := nil;
end;
procedure TForm1.Button1Click(Sender: TObject);
begin
_loadThread := TLoadThread.Create;
_loadThread.OnTerminate := ThreadTerminated;
_loadThread.Start;
AniIndicator1.Enabled := True;
end;

我以为我走在正确的轨道上，但这似乎不起作用，谁能解释一下我做错了什么？

Answer 1

您的工作线程在其Process()方法中花费了所有时间，该方法由TThread.Synchronize()调用，因此它在主 UI 线程中运行。Process()不处理 UI 消息，这就是TAniIndicator不起作用的原因。

按原样，您的工作线程完全无用。所有代码都在主 UI 线程中运行。 因此，您不妨完全摆脱TLoadThread：

procedure TForm1.FormCreate(Sender: TObject);
begin
AniIndicator1.Visible := False;
end;
procedure TForm1.BuildListView;
var
i : integer;
LI : TListViewItem;
begin
AniIndicator1.Visible := True;
AniIndicator1.Enabled := True;
ListView1.BeginUpdate;
try
for i := 1 to 2000 do
begin
LI := ListView1.Items.Add;
LI.Text := 'ListView Item ' + IntToStr(i);
if (i mod 100) = 0 then
Application.ProcessMessages;
end;
finally
ListView1.EndUpdate;
AniIndicator1.Enabled := False;
AniIndicator1.Visible := False;
end;
end;
procedure TForm1.Button1Click(Sender: TObject);
begin
BuildListView;
end;

否则，如果使用线程，则不要同步循环本身，只同步实际接触 UI 的部分：

type
TLoadThread = class(TThread)
public
constructor Create; reintroduce;
protected
procedure Execute; override;
end;
constructor TLoadThread.Create;
begin
inherited Create(True);
FreeOnTerminate := True;
end;
procedure TLoadThread.Execute;
begin
Form1.BuildListView;
end;
var
_loadThread : TLoadThread = nil;
procedure TForm1.ThreadTerminated(Sender: TObject);
begin
_loadThread := nil;
end;
procedure TForm1.FormCreate(Sender: TObject);
begin
AniIndicator1.Visible := False;
end;
procedure TForm1.BuildListView;
var
i : integer;
begin
TThread.Synchronize(nil,
procedure
begin
AniIndicator1.Visible := True;
AniIndicator1.Enabled := True;
ListView1.BeginUpdate;
end
);
try
for i := 1 to 2000 do
begin
TThread.Synchronize(nil,
procedure
var
LI : TListViewItem;
begin
LI := ListView1.Items.Add;
LI.Text := 'ListView Item ' + IntToStr(i);
end
);
end;
finally
TThread.Synchronize(nil,
procedure
begin
ListView1.EndUpdate;
AniIndicator1.Enabled := False;
AniIndicator1.Visible := False;
end
);
end;
end;
procedure TForm1.Button1Click(Sender: TObject);
begin
if _loadThread <> nil then
begin
_loadThread := TLoadThread.Create;
_loadThread.OnTerminate := ThreadTerminated;
_loadThread.Start;
end;
end;