主要解决的问题是：在屏幕处于锁屏或关闭状态下，无法正常显示MessageDlg

procedure WaitUntilScreenIsActive;

begin

  while True do

  begin

    Application.ProcessMessages;

    if isScreenOn and isKeyguardunLock then

     Break;

  end;

end;

function isScreenOn : Boolean;

var

  Native:JObject ;

  PowerManager : JPowerManager;

begin

  Native:=SharedActivityContext.getSystemService(TJContext.JavaClass.POWER_SERVICE);

  if not Assigned(Native) then

  begin

    raise Exception.Create('Could not locate Connectivity Service');

  end;

  PowerManager := TJPowerManager.Wrap((Native as ILocalObject).GetObjectID) ;

  if not Assigned(PowerManager) then

    Result := True

  else

    Result := PowerManager.isScreenOn;

  Native:=SharedActivityContext.getSystemService(TJContext.JavaClass.KEYGUARD_SERVICE);

end;

function isKeyguardunLock : Boolean;

var

  Native:JObject ;

  KeyguardManager : JKeyguardManager;

begin  Native:=SharedActivityContext.getSystemService(TJContext.JavaClass.KEYGUARD_SERVICE);

  if not Assigned(Native) then

  begin

    raise Exception.Create('Could not locate Connectivity Service');

  end;

  KeyguardManager := TJKeyguardManager.Wrap((Native as ILocalObject).GetObjectID) ;

  if not Assigned(KeyguardManager) then

    Result := True

  else

    Result := not KeyguardManager.isKeyguardLocked;

end;

来源：https://www.cnblogs.com/dannylee/p/7656656.html