//程序事件服务操作
var
  FMXApplicationEventService: IFMXApplicationEventService;
begin
  if TPlatformServices.Current.SupportsPlatformService (IFMXApplicationEventService, IInterface(FMXApplicationEventService)) then 
    FMXApplicationEventService.SetApplicationEventHandler(HandleAppEvent)
  else
     flag := false;
end;

function TForm1.HandleAppEvent(AAppEvent: TApplicationEvent; AContext: TObject)   : boolean; 
begin 
  if flag = false then
    exit;
  case AAppEvent of
    TApplicationEvent.aeEnteredBackground:
      begin
          //当程序后台运行了
      end;
  end;
  Result := true;
end;

//退出键操作
procedure TPForm.FormKeyUp(Sender: TObject; var Key: Word; var KeyChar: Char;
  Shift: TShiftState);
begin
  if Key = vkHardwareBack then
  begin
    {$IFDEF ANDROID}
    MessageDlg('确认退出吗？', System.UITypes.TMsgDlgType.mtInformation,
    [
      System.UITypes.TMsgDlgBtn.mbYes,
      //System.UITypes.TMsgDlgBtn.mbNo,
      System.UITypes.TMsgDlgBtn.mbCancel
    ], 0, System.UITypes.TMsgDlgBtn.mbCancel,
    procedure(const AResult: TModalResult)
    begin
      if AResult = mrYES then
         MainActivity.finish; { 退出程序 }   // use FMX.Platform.Android
      end);
    {$ENDIF ANDROID}
    //close;
    Key := 0;
    exit;
  end;
end;