如何读取按键输入？

Question

我正在尝试拥有一个键控摄像头。 TForm 没有 Onkeypress，所以我如何从键盘读取此输入？

procedure TForm2.FormKeyPress(Sender: TObject; var Key: Char);
var
  ok: boolean;
begin
  ok := true;
  case Key of
    'a': camera1.Position.y:=camera1.Position.y+1;
    'A': camera1.Position.y:=camera1.Position.y+1;
    'd': camera1.Position.y:=camera1.Position.y-1;
    'D': camera1.Position.y:=camera1.Position.y-1;
    'w': camera1.Position.X:=camera1.Position.X-1;
    'W': camera1.Position.X:=camera1.Position.X-1;
    'x': camera1.Position.X:=camera1.Position.X+1;
    'X': camera1.Position.X:=camera1.Position.X+1;
    'q': camera1.RotationAngle.z := camera1.RotationAngle.z-1;
    'Q': camera1.RotationAngle.z := camera1.RotationAngle.z-1;
    'e': camera1.RotationAngle.z := camera1.RotationAngle.z+1;
    'E': camera1.RotationAngle.z := camera1.RotationAngle.z+1;
    'z': camera1.Position.z:=camera1.Position.z+1;
    'Z': camera1.Position.z:=camera1.Position.z+1;
    'c': camera1.Position.z:=camera1.Position.z-1;
    'C': camera1.Position.z:=camera1.Position.z-1;
    else
      ok := false;
  end; {case}
  //if ok then
   // Invalidate;
  positionChange(camera1);
  RotationAngleChange(camera1);
end;

Answer 1

更新到最新版本的 XE2（AFAIK Update 4 Hotfix 1）和

请改用 TForm.OnKeyDown 或 TForm.OnKeyUp 事件。这是我使用的快速测试：

procedure TForm1.FormKeyDown(Sender: TObject; var Key: Word; var KeyChar: Char;
  Shift: TShiftState);
begin
  case KeyChar of
    'A'..'Z', 'a'..'z': Caption := 'Got an alpha ' + KeyChar;
    '0'..'9': Caption := 'Got a number ' + KeyChar;
  else
    Caption := 'Got something else ' + KeyChar;
  end;
  KeyChar := #0;
end;

根据Embarcadero forums post，在没有上述更新的 XE2 中，您需要实际覆盖 TForm.KeyDown 事件（根据 @TLama 的请求添加；他是找到它并在 cmets 中发布我的答案的人）：

type
  TForm1 = class(TForm)
    Memo1: TMemo;
  private
  public
    procedure KeyDown(var Key: Word; var KeyChar: Char; 
      Shift: TShiftState); override;
  end;

implementation

procedure TForm1.KeyDown(Sender: TObject; var Key: Word; var KeyChar: Char;
  Shift: TShiftState);
begin
  case KeyChar of
    'A'..'Z', 'a'..'z': Caption := 'Got an alpha ' + KeyChar;
    '0'..'9': Caption := 'Got a number ' + KeyChar;
  else
    Caption := 'Got something else ' + KeyChar;
  end;
  KeyChar := #0;
end;

（请注意，您可以稍微缩短代码）：

procedure TForm1.FormKeyDown(Sender: TObject; var Key: Word; var KeyChar: Char;
  Shift: TShiftState);
begin
  ok := true;
  case KeyChar of
    'A', 'a': camera1.Position.y:=camera1.Position.y+1;
    'D', 'd': camera1.Position.y:=camera1.Position.y-1;
    'W', 'w': camera1.Position.X:=camera1.Position.X-1;
    'X', 'x': camera1.Position.X:=camera1.Position.X+1;
    'Q', 'q': camera1.RotationAngle.z := camera1.RotationAngle.z-1;
    'E', 'e': camera1.RotationAngle.z := camera1.RotationAngle.z+1;
    'Z', 'z': camera1.Position.z:=camera1.Position.z+1;
    'C', 'c': camera1.Position.z:=camera1.Position.z-1;
  else
    ok := false;
  end; {case}
  if ok then
  begin
   // Invalidate;
   KeyChar := #0;  // Remove keystroke, because you've handled it
  end;
  positionChange(camera1);
  RotationAngleChange(camera1);      
end;