我怎样才能让我的Andr​​oid应用程序反应后退按钮？

How can I make my Android app react to the back-button?

有什么作为高层次的VCL的TApplicationEvents来处理它，或者我需要潜水深入到这里的低级别的Andr​​oid特有的东西？

Is there something as high-level VCL's TApplicationEvents to handle it, or do I need to dive deep into low-level Android-specific stuff here?

目前，大多数的演示应用程序有一个屏幕上的后退按钮返回到previous屏幕。 $ P $总是pssing的psysical按钮似乎退出程序，而在某些情况下，它会导致访问冲突

Right now, most of the demo applications have an on-screen back button to go back to a previous screen. Pressing the psysical button always seems to quit the app, and in some situations it results in an access violation.

推荐答案

在表单的 OnKey ... 活动时，键参数 vkHardwareBack 在Android上。例如：

In the form's OnKey... events, the Key parameter is vkHardwareBack on Android. For example:

uses
  FMX.Platform, FMX.VirtualKeyboard;

procedure TForm1.FormKeyUp(Sender: TObject; var Key: Word; var KeyChar: Char; Shift: TShiftState);
var
  FService : IFMXVirtualKeyboardService;
begin
  if Key = vkHardwareBack then
  begin
    TPlatformServices.Current.SupportsPlatformService(IFMXVirtualKeyboardService, IInterface(FService));
    if (FService <> nil) and (vksVisible in FService.VirtualKeyBoardState) then
    begin
      // Back button pressed, keyboard visible, so do nothing...
    end else
    begin
      // Back button pressed, keyboard not visible or not supported on this platform, lets exit the app...
      if MessageDlg('Exit Application?', TMsgDlgType.mtConfirmation, [TMsgDlgBtn.mbOK, TMsgDlgBtn.mbCancel], -1) = mrOK then
      begin
        // Exit application here...
      end else
      begin
        // They changed their mind, so ignore the Back button press...
        Key := 0;
      end;
    end;
  end
  ...
end;