如何在滚动框上创建减速滚动效果? [英] How to create a slowing scroll effect on a scrollbox?

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本文介绍了如何在滚动框上创建减速滚动效果?的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

我喜欢在滚动框中平移图像后创建平滑的减速滚动效果.就像在 maps.google.com 中平移地图一样.我不确定它是什么类型，但行为完全相同:在快速移动地图时，它不会在您松开鼠标时立即停止，而是开始放慢速度.

I like to create a smooth slowing scroll effect after panning an image in a scrollbox. Just like panning the map in maps.google.com. I'm not sure what type it is, but exactly same behaviour: when dragging the map around with a fast move, it doesn't stop immediately when you release the mouse, but it starts slowing down.

任何想法、组件、链接或示例?

Any ideas, components, links or samples?

推荐答案

思路:

根据您的评论，它应该感觉像谷歌地图，因此在拖动图像时，图像应该粘在鼠标指针上；目前不需要特殊效果.但是在释放鼠标按钮时，图像需要在同一方向上进一步移动(滚动框需要平移)，并以逐渐缓和的速度开始，从释放鼠标按钮时的拖动速度开始.

The idea:

As per your comment, it should feel like Google Maps and thus while dragging the image, the image should stick to the mouse pointer; no special effects required so far. But at releasing the mouse button, the image needs to move (the scroll box needs to pan) further in the same direction and with a gradually easing speed, starting with the dragging velocity at the moment the mouse button was released.

所以我们需要:

  • 按下鼠标时的拖动处理程序:OnMouseMove 将起作用，
  • 松开鼠标时的平移速度:在拖动操作过程中，我们会用定时器跟踪最新的速度，
  • 鼠标释放后仍然移动图像的东西:我们使用相同的计时器，
  • 一种更新 GUI 的方法:更新图像位置、滚动滚动框和更新滚动条位置.幸运的是，设置滚动框滚动条的位置就可以了，
  • 释放鼠标后逐渐降低速度的功能.我选择了一个简单的线性因子，但您可以试验一下.
  • 在表单上放置一个 TScrollBox，为 OnMouseDown、OnMouseMove 和 OnMouseUp 创建事件处理程序并设置DoubleBuffered 属性为 True(这需要运行时完成)，
  • 在表单上放置一个 TTimer，将其间隔设置为 15 毫秒(~ 67 Hz 刷新率)并为 OnTimer 创建一个事件处理程序，
  • 在滚动框上放置一个 TImage，加载一张图片，将大小设置为大一些(例如 3200 x 3200)，将 Stretch 设置为 True 并将 Enabled 设置为 False 以让鼠标事件通过滚动框.
  • Drop a TScrollBox on your form, create event handlers for OnMouseDown, OnMouseMove and OnMouseUp and set the DoubleBuffered property to True (this needs to be done runtime),
  • Drop a TTimer on your form, set its interval to 15 milliseconds (~ 67 Hz refresh rate) and create an event handler for OnTimer,
  • Drop a TImage on the scroll box, load a picture, set the size to something big (e.g. 3200 x 3200), set Stretch to True and set Enabled to False to let the mouse events through to the scroll box.
unit Unit1;

interface

uses
  Windows, SysUtils, Classes, Controls, Forms, JPEG, ExtCtrls, StdCtrls;

type
  TForm1 = class(TForm)
    ScrollBox: TScrollBox;
    Image: TImage;
    TrackingTimer: TTimer;
    procedure ScrollBoxMouseDown(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
    procedure ScrollBoxMouseMove(Sender: TObject; Shift: TShiftState; X,
      Y: Integer);
    procedure ScrollBoxMouseUp(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
    procedure TrackingTimerTimer(Sender: TObject);
    procedure FormCreate(Sender: TObject);
  private
    FDragging: Boolean;
    FPrevScrollPos: TPoint;
    FPrevTick: Cardinal;
    FSpeedX: Single;
    FSpeedY: Single;
    FStartPos: TPoint;
    function GetScrollPos: TPoint;
    procedure SetScrollPos(const Value: TPoint);
  public
    property ScrollPos: TPoint read GetScrollPos write SetScrollPos;
  end;

implementation

{$R *.dfm}

procedure TForm1.FormCreate(Sender: TObject);
begin
  ScrollBox.DoubleBuffered := True;
end;

function TForm1.GetScrollPos: TPoint;
begin
  with ScrollBox do
    Result := Point(HorzScrollBar.Position, VertScrollBar.Position);
end;

procedure TForm1.ScrollBoxMouseDown(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  FDragging := True;
  FPrevTick := GetTickCount;
  FPrevScrollPos := ScrollPos;
  TrackingTimer.Enabled := True;
  FStartPos := Point(ScrollPos.X + X, ScrollPos.Y + Y);
  Screen.Cursor := crHandPoint;
end;

procedure TForm1.ScrollBoxMouseMove(Sender: TObject; Shift: TShiftState;
  X, Y: Integer);
begin
  if FDragging then
    ScrollPos := Point(FStartPos.X - X, FStartPos.Y - Y);
end;

procedure TForm1.ScrollBoxMouseUp(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  FDragging := False;
  Screen.Cursor := crDefault;
end;

procedure TForm1.SetScrollPos(const Value: TPoint);
begin
  ScrollBox.HorzScrollBar.Position := Value.X;
  ScrollBox.VertScrollBar.Position := Value.Y;
end;

procedure TForm1.TrackingTimerTimer(Sender: TObject);
var
  Delay: Cardinal;
begin
  Delay := GetTickCount - FPrevTick;
  if FDragging then
  begin
    if Delay = 0 then
      Delay := 1;
    FSpeedX := (ScrollPos.X - FPrevScrollPos.X) / Delay;
    FSpeedY := (ScrollPos.Y - FPrevScrollPos.Y) / Delay;
  end
  else
  begin
    if (Abs(FSpeedX) < 0.005) and (Abs(FSpeedY) < 0.005) then
      TrackingTimer.Enabled := False
    else
    begin
      ScrollPos := Point(FPrevScrollPos.X + Round(Delay * FSpeedX),
        FPrevScrollPos.Y + Round(Delay * FSpeedY));
      FSpeedX := 0.83 * FSpeedX;
      FSpeedY := 0.83 * FSpeedY;
    end;
  end;
  FPrevScrollPos := ScrollPos;
  FPrevTick := GetTickCount;
end;

end.

代码(用于面板):

如果您不想要滚动条，请使用以下代码.该示例使用面板作为容器，但它可以是任何窗口控件或表单本身.

Code (for panel):

And in case you do not want the scroll bars then use the following code. The example uses a panel as container, but that could be any windowed control or the form itself.

unit Unit2;

interface

uses
  Windows, SysUtils, Classes, Controls, Forms, JPEG, ExtCtrls, Math;

type
  TForm2 = class(TForm)
    Panel: TPanel;
    Image: TImage;
    TrackingTimer: TTimer;
    procedure PanelMouseDown(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
    procedure PanelMouseMove(Sender: TObject; Shift: TShiftState; X,
      Y: Integer);
    procedure PanelMouseUp(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
    procedure TrackingTimerTimer(Sender: TObject);
    procedure FormCreate(Sender: TObject);
  private
    FDragging: Boolean;
    FPrevImagePos: TPoint;
    FPrevTick: Cardinal;
    FSpeedX: Single;
    FSpeedY: Single;
    FStartPos: TPoint;
    function GetImagePos: TPoint;
    procedure SetImagePos(Value: TPoint);
  public
    property ImagePos: TPoint read GetImagePos write SetImagePos;
  end;

implementation

{$R *.dfm}

procedure TForm2.FormCreate(Sender: TObject);
begin
  Panel.DoubleBuffered := True;
end;

function TForm2.GetImagePos: TPoint;
begin
  Result.X := Image.Left;
  Result.Y := Image.Top;
end;

procedure TForm2.PanelMouseDown(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  FDragging := True;
  FPrevTick := GetTickCount;
  FPrevImagePos := ImagePos;
  TrackingTimer.Enabled := True;
  FStartPos := Point(X - Image.Left, Y - Image.Top);
  Screen.Cursor := crHandPoint;
end;

procedure TForm2.PanelMouseMove(Sender: TObject; Shift: TShiftState; X,
  Y: Integer);
begin
  if FDragging then
    ImagePos := Point(X - FStartPos.X, Y - FStartPos.Y);
end;

procedure TForm2.PanelMouseUp(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  FDragging := False;
  Screen.Cursor := crDefault;
end;

procedure TForm2.SetImagePos(Value: TPoint);
begin
  Value.X := Max(Panel.ClientWidth - Image.Width, Min(0, Value.X));
  Value.Y := Max(Panel.ClientHeight - Image.Height, Min(0, Value.Y));
  Image.SetBounds(Value.X, Value.Y, Image.Width, Image.Height);
end;

procedure TForm2.TrackingTimerTimer(Sender: TObject);
var
  Delay: Cardinal;
begin
  Delay := GetTickCount - FPrevTick;
  if FDragging then
  begin
    if Delay = 0 then
      Delay := 1;
    FSpeedX := (ImagePos.X - FPrevImagePos.X) / Delay;
    FSpeedY := (ImagePos.Y - FPrevImagePos.Y) / Delay;
  end
  else
  begin
    if (Abs(FSpeedX) < 0.005) and (Abs(FSpeedY) < 0.005) then
      TrackingTimer.Enabled := False
    else
    begin
      ImagePos := Point(FPrevImagePos.X + Round(Delay * FSpeedX),
        FPrevImagePos.Y + Round(Delay * FSpeedY));
      FSpeedX := 0.83 * FSpeedX;
      FSpeedY := 0.83 * FSpeedY;
    end;
  end;
  FPrevImagePos := ImagePos;
  FPrevTick := GetTickCount;
end;

end.

代码(油漆盒):

当图像的尺寸是无限的(例如地球仪)时，您可以使用油漆盒将图像的末端粘在一起.

Code (for paint box):

And when the image's dimensions are limitless (e.g. a globe), you can use a paint box to glue the image's ends together.

unit Unit3;

interface

uses
  Windows, SysUtils, Classes, Graphics, Controls, Forms, ExtCtrls, JPEG;

type
  TForm3 = class(TForm)
    Painter: TPaintBox;
    Tracker: TTimer;
    procedure FormCreate(Sender: TObject);
    procedure FormDestroy(Sender: TObject);
    procedure PainterMouseDown(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
    procedure PainterMouseMove(Sender: TObject; Shift: TShiftState; X,
      Y: Integer);
    procedure PainterMouseUp(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
    procedure PainterPaint(Sender: TObject);
    procedure TrackerTimer(Sender: TObject);
  private
    FDragging: Boolean;
    FGraphic: TGraphic;
    FOffset: Integer;
    FPrevOffset: Integer;
    FPrevTick: Cardinal;
    FSpeed: Single;
    FStart: Integer;
    procedure SetOffset(Value: Integer);
  public
    property Offset: Integer read FOffset write SetOffset;
  end;

implementation

{$R *.dfm}

procedure TForm3.FormCreate(Sender: TObject);
begin
  DoubleBuffered := True;
  FGraphic := TJPEGImage.Create;
  FGraphic.LoadFromFile('gda_world_map_small.jpg');
  Constraints.MaxWidth := FGraphic.Width + 30;
end;

procedure TForm3.FormDestroy(Sender: TObject);
begin
  FGraphic.Free;
end;

procedure TForm3.PainterMouseDown(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  FDragging := True;
  FPrevTick := GetTickCount;
  FPrevOffset := Offset;
  Tracker.Enabled := True;
  FStart := X - FOffset;
  Screen.Cursor := crHandPoint;
end;

procedure TForm3.PainterMouseMove(Sender: TObject; Shift: TShiftState; X,
  Y: Integer);
begin
  if FDragging then
    Offset := X - FStart;
end;

procedure TForm3.PainterMouseUp(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  FDragging := False;
  Screen.Cursor := crDefault;
end;

procedure TForm3.PainterPaint(Sender: TObject);
begin
  Painter.Canvas.Draw(FOffset, 0, FGraphic);
  Painter.Canvas.Draw(FOffset + FGraphic.Width, 0, FGraphic);
end;

procedure TForm3.SetOffset(Value: Integer);
begin
  FOffset := Value;
  if FOffset < -FGraphic.Width then
  begin
    Inc(FOffset, FGraphic.Width);
    Dec(FStart, FGraphic.Width);
  end
  else if FOffset > 0 then
  begin
    Dec(FOffset, FGraphic.Width);
    Inc(FStart, FGraphic.Width);
  end;
  Painter.Invalidate;
end;

procedure TForm3.TrackerTimer(Sender: TObject);
var
  Delay: Cardinal;
begin
  Delay := GetTickCount - FPrevTick;
  if FDragging then
  begin
    if Delay = 0 then
      Delay := 1;
    FSpeed := (Offset - FPrevOffset) / Delay;
  end
  else
  begin
    if Abs(FSpeed) < 0.005 then
      Tracker.Enabled := False
    else
    begin
      Offset := FPrevOffset + Round(Delay * FSpeed);
      FSpeed := 0.83 * FSpeed;
    end;
  end;
  FPrevOffset := Offset;
  FPrevTick := GetTickCount;
end;

end.

这篇关于如何在滚动框上创建减速滚动效果?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！

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