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Crear una página web de presentación

  • Artículo

El código de ejemplo de esta sección usa la API de punto de control con tecnología UPnP para crear una página web sencilla para controlar dispositivos multimedia basados en UPnP ficticios. La página web se muestra en la ilustración siguiente.

Nota

Este código de ejemplo solo funciona para exploradores que se ejecutan en Windows; no funciona en exploradores que se ejecutan en otros sistemas operativos.

 

presentación de ejemplo de una página web

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML>

<HEAD>
<TITLE>Presentation page for an emulated UPnP midi player 
     device</TITLE>
</HEAD>

<BODY>

<BR>
<!--Set up the controls-->
Open media file: <INPUT type="TEXT" value="c:\travels.mid" 
     ID="FileName" NAME="FileName" SIZE="50,5" MAXLENGTH="250">
<BR>
<BR>

<INPUT type="button" ID="PlayButton" onclick="OnPlay()" 
     value="Play >>">
<INPUT type="button" ID="PauseButton" onclick="OnPause(this)" 
     value="Pause">
<INPUT type="button" ID="StopButton" onclick="OnStop()" value="Stop">
<INPUT type="button" ID="VolUpButton" onclick="OnVolumeUp()" 
     value="VolumeUp">
<INPUT type="button" ID="VolDownButton" onclick="OnVolumeDown()" 
     value="VolumeDown">

<H3>App State</H3>

<!--Set up the table that displays state information-->
<TABLE BGCOLOR='#D6D7DE' BORDER=0 VALIGN=top ALIGN=left CELLPADDING=1 
     CELLSPACING=3 height="157">

  <TR>
    <TD BGCOLOR='#000000' VALIGN=center ALIGN=center WIDTH=60 
         height="17"><B><FONT SIZE="2" 
         COLOR=whitesmoke>Variable</FONT></B></TD>
    <TD VALIGN=middle ALIGN=left BGCOLOR='#000000' WIDTH=470 
         height="17"><B><FONT SIZE="2" 
         COLOR=whitesmoke>&nbsp;&nbsp;Value</FONT></B></TD>
  </TR>

  <TR>
    <TD BGCOLOR="#FFFFFF" VALIGN=center ALIGN=center 
         height="59">File</TD>
    <TD BGCOLOR="#FFFFFF" valign="top" height="59">&nbsp;&nbsp;<P 
         ID=MyFile></P></TD>
  </TR>

  <TR>
    <TD  BGCOLOR="#FFFFFF" VALIGN=center ALIGN=center 
         height="59">Volume</TD>
    <TD  BGCOLOR="#FFFFFF" valign="top" height="59">&nbsp;&nbsp;<P 
         ID=Volume></P></TD>
  </TR>

</TABLE>

<SCRIPT language=VBScript>

<!--Initialize the set of services offered by the device, and other variables-->
Dim appService
Dim xportService
Dim Vol(1)
Dim args(0)
Dim File(1)
Dim bPlaying
Dim bPaused
Dim device

set appService=Nothing
set xportService=Nothing
bPlaying = False
bPaused = False

<!--Create the description document object-->
Dim descriptionDoc
Set descriptionDoc = CreateObject("UPnP.DescriptionDocument")

<!--Load the description doc for the device-->
descriptionDoc.Load("./description.xml")

device = descriptionDoc.RootDevice

<!--Connect to the device's DVDVideo and AVTTransport services-->
set xportService = device.Services("urn:upnp-org:serviceId:DVDVideo")
set appService = device.Services("urn:upnp-org:serviceId:AVTransport")

appService.AddCallback GetRef("eventHandler")

<!--initialize the volume-->
Dim outArgs (0)

Vol(0) = 3
appService.InvokeAction "SetVolume", Vol, outArgs

<!--Event handler for the appService-->
<!--Update the state table maintained locally-->
Sub eventHandler(callbackType, svcObj, varName, value)
  If (callbackType = "VARIABLE_UPDATE") Then
       select case svcObj.Id
            case "upnp:id:mediaapp"
                 select case varName
                      Case "File" MyFile.innerText = value
                                  FileName.value = value
                      Case "Volume" Volume.innerText = value
                 end select
       end select
    End If
End Sub

<!--Invoke the play action-->
function OnPlay ()
  File(0) = FileName.value
  Dim outArgs(0)

  If File(0) = "" Then
       alert("Please enter the path to the file to play!")
  Else
       appService.InvokeAction "Power", args, outArgs
       appService.InvokeAction "LoadFile", File, outArgs
       xportService.InvokeAction "Play", args, outArgs

       bPlaying = True
  End if
end function

<!--Invoke the Pause action-->
function OnPause (button)
   Dim outArgs (0)

  If bPlaying Then
       xportService.InvokeAction "Pause", args, outArgs
       bPaused = True
       bPlaying = False
  ElseIf bPaused Then
       xportService.InvokeAction "Play", args, outArgs
       bPaused = False
       bPlaying = True
  End if

  If bPaused Then
       button.value="Resume"
  Else
       button.value="Pause"
  End if
end function

<!--Invoke the Stop action-->
function OnStop ()
   Dim outArgs (0)

  xportService.InvokeAction "Stop", args, outArgs
  bPlaying = False
end function

<!--Invoke the VolumeUp action-->
function OnVolumeUp ()
   Dim outArgs (0)

  appService.InvokeAction "VolumeUp", args, outArgs
end function

<!--Invoke the VolumeDown action-->
function OnVolumeDown ()
   Dim outArgs (0)

  appService.InvokeAction "VolumeDown", args, outArgs
end function

</SCRIPT>

</BODY>

</HTML>