主线程被阻止时显示活动指示符(继续)

Question

继续上一个问题 我希望即使主线程被阻止也能显示一些活动指示.(基于这篇文章).

基于附加代码的问题:

• 使用Synchronize(PaintTargetWindow);不会绘制窗口
• 我有时会收到一个错误: Canvas does not allow drawing.在行中:{FBitmap.}StretchDraw(Rect(Left, ImageRect.Top, Right, ImageRect.Bottom), FfgPattern)

这是我用来创建指标线程的代码:

unit AniThread;

interface

uses Windows, Classes, Graphics, Controls, Math;

const
  ANI_GRAD_FG_COLOR_BAGIN = $00CDFFCD;
  ANI_GRAD_FG_COLOR_END   = $0024B105;
  ANI_GRAD_BK_COLOR_BAGIN = $00F5F5F5;
  ANI_GRAD_BK_COLOR_END   = $00BDBDBD;

type
  TAnimationThread = class(TThread)
  private
    FWnd: HWND;
    FPaintRect: TRect;
    FInterval: Integer;
    FfgPattern, FbkPattern: TBitmap;
    FBitmap: TBitmap;
    FImageRect: TRect;
    procedure UpdatePattern(Pattern: TBitmap; ColorBegin, ColorEnd: TColor);
    function CreatePatternBitmap(AColorBegin, AColorEnd: TColor): TBitmap;
    procedure PaintTargetWindow;
  protected
    procedure Execute; override;
  public
    procedure Animate;
    constructor Create(PaintSurface: TWinControl; { Control to paint on }
      PaintRect: TRect;          { area for animation bar }
      Interval: Integer          { wait in msecs between paints}
      );
    destructor Destroy; override;
  end;

implementation

constructor TAnimationThread.Create(PaintSurface: TWinControl;
  PaintRect: TRect;
  Interval: Integer);
begin
  inherited Create(True); { suspended }
  FreeOnterminate := True;
  Priority := tpHigher;
  FInterval := Interval;
  FWnd := PaintSurface.Handle;
  FPaintRect := PaintRect;
  FfgPattern := CreatePatternBitmap(ANI_GRAD_FG_COLOR_BAGIN, ANI_GRAD_FG_COLOR_END);
  FbkPattern := CreatePatternBitmap(ANI_GRAD_BK_COLOR_BAGIN, ANI_GRAD_BK_COLOR_END);
end;

destructor TAnimationThread.Destroy;
begin
  inherited Destroy;
  FfgPattern.Free;
  FbkPattern.Free;
end;

procedure TAnimationThread.Animate;
begin
  Resume;
  Sleep(0);
end;

function TAnimationThread.CreatePatternBitmap(AColorBegin, AColorEnd: TColor): TBitmap;
begin
  Result := TBitmap.Create;
  Result.PixelFormat := pf24bit;
  UpdatePattern(Result, AColorBegin, AColorEnd);
end;

type
  PRGBTripleArray = ^TRGBTripleArray;
  TRGBTripleArray = array[0..32767] of TRGBTriple;
  TGradientColors = array[0..255] of TRGBTriple;

procedure PatternBuilder(const Colors: TGradientColors; Pattern: TBitmap);
var
  Y: Integer;
  Row: PRGBTripleArray;
begin
  Pattern.Width := 1;
  Pattern.Height := 256;
  for Y := 0 to 127 do
  begin
    Row := PRGBTripleArray(Pattern.ScanLine[Y]);
    Row[0] := Colors[Y];
    Row := PRGBTripleArray(Pattern.ScanLine[Y + 128]);
    Row[0] := Colors[255 - Y];
  end;
end;

procedure TAnimationThread.UpdatePattern(Pattern: TBitmap; ColorBegin, ColorEnd: TColor);
var
  Colors: TGradientColors;
  dRed, dGreen, dBlue: Integer;
  RGBColor1, RGBColor2: TColor;
  RGB1, RGB2: TRGBTriple;
  Index: Integer;
begin
  RGBColor1 := ColorToRGB(ColorBegin);
  RGBColor2 := ColorToRGB(ColorEnd);

  RGB1.rgbtRed := GetRValue(RGBColor1);
  RGB1.rgbtGreen := GetGValue(RGBColor1);
  RGB1.rgbtBlue := GetBValue(RGBColor1);

  RGB2.rgbtRed := GetRValue(RGBColor2);
  RGB2.rgbtGreen := GetGValue(RGBColor2);
  RGB2.rgbtBlue := GetBValue(RGBColor2);

  dRed := RGB2.rgbtRed - RGB1.rgbtRed;
  dGreen := RGB2.rgbtGreen - RGB1.rgbtGreen;
  dBlue := RGB2.rgbtBlue - RGB1.rgbtBlue;

  for Index := 0 to 255 do
    with Colors[Index] do
    begin
      rgbtRed := RGB1.rgbtRed + (Index * dRed) div 255;
      rgbtGreen := RGB1.rgbtGreen + (Index * dGreen) div 255;
      rgbtBlue := RGB1.rgbtBlue + (Index * dBlue) div 255;
    end;

  PatternBuilder(Colors, Pattern);
end;

procedure TAnimationThread.PaintTargetWindow;
var
  DC: HDC;
begin
  DC := GetDC(FWnd);
  if DC <> 0 then
    try
      BitBlt(DC,
        FPaintRect.Left,
        FPaintRect.Top,
        FImageRect.Right,
        FImageRect.Bottom,
        FBitmap.Canvas.handle,
        0, 0,
        SRCCOPY);
    finally
      ReleaseDC(FWnd, DC);
    end;
end;

procedure TAnimationThread.Execute;
var
  Left, Right: Integer;
  Increment: Integer;
  State: (incRight, incLeft, decLeft, decRight);
begin
  InvalidateRect(FWnd, nil, True);
  FBitmap := TBitmap.Create;
  try
    with FBitmap do
    begin
      Width := FPaintRect.Right - FPaintRect.Left;
      Height := FPaintRect.Bottom - FPaintRect.Top;
      FImageRect := Rect(0, 0, Width, Height);
    end;
    Left := 0;
    Right := 0;
    Increment := FImageRect.Right div 50;
    State := Low(State);
    while not Terminated do
    begin
      with FBitmap.Canvas do
      begin
        StretchDraw(FImageRect, FbkPattern);
        case State of
          incRight:
            begin
              Inc(Right, Increment);
              if Right > FImageRect.Right then begin
                Right := FImageRect.Right;
                Inc(State);
              end;
            end;
          incLeft:
            begin
              Inc(Left, Increment);
              if Left >= Right then begin
                Left := Right;
                Inc(State);
              end;
            end;
          decLeft:
            begin
              Dec(Left, Increment);
              if Left <= 0 then begin
                Left := 0;
                Inc(State);
              end;
            end;
          decRight:
            begin
              Dec(Right, Increment);
              if Right <= 0 then begin
                Right := 0;
                State := incRight;
              end;
            end;
        end;

        StretchDraw(Rect(Left, FImageRect.Top, Right, FImageRect.Bottom), FfgPattern);
      end; { with }

      // Synchronize(PaintTargetWindow); // not painting when the main thread is blocked
      PaintTargetWindow;

      SleepEx(FInterval, False);
    end; { While }
  finally
    FBitmap.Free;
  end;
end;

end.

用法:在主窗体上删除a TButton和a TPanel.

uses AniThread;

procedure TForm1.Button1Click(Sender: TObject);
var
  at: TAnimationThread;
begin
  at := TAnimationThread.Create(Panel1, Panel1.ClientRect, 10);
  Button1.Enabled := False;
  try
    at.Animate;
    Sleep(3000); // sleep 3 sec. block main thread
  finally
    at.Terminate;
    Button1.Enabled := True;
  end;
end;

我知道很多人会对这种方法不满意.但现在,让我的工作做得好,对我来说主要是一个挑战.任何有关此问题的帮助将不胜感激.

编辑:

这是原始文章(由Peter Below,TeamB提供).我只实现了渐变画.

Answer 1

同样，在窗口上绘图的唯一线程安全方法是从创建窗口的同一线程进行绘图；其他任何东西都是不安全的。

作为可能的解释，为什么您的代码可以在旧的 Windows 版本上运行良好，而不能在现代版本中运行，请阅读这篇旧的新事物文章。