如何在roku视频播放器上显示图像

Question

我试图在播放视频时在roku视频播放器上显示图像，但它不起作用。这是我的代码：

function player(video_id as String,stream as String,streamTitle as String,subtitle_url as String,position as String)

    print "play: "+stream
    p = CreateObject("roMessagePort")
    video = CreateObject("roVideoScreen")
    video.setMessagePort(p)

    videoclip = CreateObject("roAssociativeArray")
    videoclip.StreamBitrates = [0]
    videoclip.StreamUrls = [stream]

    di = CreateObject("roDeviceInfo")
    if di.GetDisplayType() = "HDTV" then 
        videoclip.streamqualities=["HD"]
    else
        videoclip.streamqualities=["SD"]
    end if

    videoclip.PlayStart=position.toint()

    videoclip.StreamFormat = "hls"
    videoclip.switchingstrategy="full-adaptation"
    videoclip.Title = streamTitle
    if subtitle_url<>invalid
        videoclip.SubtitleUrl = subtitle_url
    end if

    lastSavedPos   = 0
    statusInterval = 10
    nowpos=0


    video.SetPositionNotificationPeriod(10)
    video.SetContent(videoclip)
    video.show()
    showImageCanvas()
    while true
        msg = wait(0, video.GetMessagePort())
        if type(msg) = "roVideoScreenEvent"
            if msg.isScreenClosed() then 'ScreenClosed event
                return "incomplete"
                exit while                
            else if msg.isFullResult()
                SetXtraData(video_id,"0")
                return "completed"
            else if msg.isResumed()
                SetXtraData(video_id,nowpos.tostr())
            else if msg.isPlaybackPosition() then

                nowpos = msg.GetIndex()
                if nowpos > 120
                    if abs(nowpos - lastSavedPos) > statusInterval
                        lastSavedPos = nowpos
                        SetXtraData(video_id,nowpos.tostr())               
                    end if
                end if
            else if msg.isRequestFailed()
                showMessage("Information","Something went wrong while we tried to play the video")
            else
                print "Unknown event: "; msg.GetType(); " msg: "; msg.GetMessage()
                 showImageCanvas()
            endif
        end if
    end while
end function





Sub showImageCanvas()
    canvasItems = [
        { 
            url:"http://www.rd.com/wp-content/uploads/sites/2/2016/04/01-cat-wants-to-tell-you-laptop.jpg"
            TargetRect:{x:189,y:300,w:100,h:100}
        }
    ]

   canvas = CreateObject("roImageCanvas")
   port = CreateObject("roMessagePort")
   canvas.SetMessagePort(port)
   'Set opaque background
   'canvas.SetLayer(0, {Color:"#FF000000", CompositionMode:"Source"})
   canvas.SetRequireAllImagesToDraw(true)
   canvas.SetLayer(1, canvasItems)
   canvas.Show()
   while(true)
       msg = wait(0,port)
       if type(msg) = "roImageCanvasEvent" then
           if (msg.isRemoteKeyPressed()) then
               i = msg.GetIndex()
               print "Key Pressed - " ; msg.GetIndex()
               if (i = 2) then
                   ' Up - Close the screen.
                   canvas.close()
               end if
           else if (msg.isScreenClosed()) then
               print "Closed"
               return
           end if
       end if
   end while
End Sub

我一直把这个showImageCanvas()放在任何地方试图让它工作，但它不起作用。请帮忙。