Roku Brightscript How to refresh image with Poster object

Question

I have 1 http address to load images that change with timestamp.

For example xxx.com?time=192186577

Can I use a Poster object to do this real-time refresh of the image content? If the poster doesn't support it, can I use another object? Please give me some help.

The code I'm implementing the Poster component

<?xml version="1.0" encoding="utf-8" ?> 
<component name="posterScene" extends="Scene" >

<script type="text/brightscript" >



<!-- m.poster.ObserveField("loadStatus", "changetext") -->
        

<![CDATA[

sub init()

    m.timer = m.top.findNode("exampleTimer")
    m.timer.ObserveField("fire", "changetexta")
    m.timer.control = "start"

    m.mirrorUrl = "http://192.168.11.6:4998/screenmirroring" 

    m.poster = m.top.findNode("channelbugPoster")

    m.top.setFocus(true)
end sub

sub changetexta()
    time = CreateObject("roDateTime")
    second = time.AsSeconds()
    milisecond = time.GetMilliseconds()
    timestampString = second.ToStr() + milisecond.ToStr()
    mirrorUrl=m.mirrorUrl+"?ts="+timestampString
    print(mirrorUrl)
    m.poster.uri = mirrorUrl
    
end sub

]]>
</script>

<children>
    <Poster
        id="channelbugPoster"
    uri="http://192.168.11.6:4998/screenmirroring?ts=1627150215328"
    width="1080"
    height="720"
    translation="[0,0]" />

    <Timer 
      id = "exampleTimer" 
      repeat = "true" 
      duration = "0.03" />

</children>

</component>

Main.brs

'********** Copyright 2015 Roku Corp.  All Rights Reserved. **********

sub Main()
    showChannelSGScreen()
end sub

sub showChannelSGScreen()
    print "in showChannelSGScreen"
    screen = CreateObject("roSGScreen")
    m.port = CreateObject("roMessagePort")
    screen.setMessagePort(m.port)
    scene = screen.CreateScene("posterScene")
    screen.show()

    while(true)

        msg = wait(0, m.port)
        msgType = type(msg)

        if msgType = "roSGScreenEvent"

            if msg.isScreenClosed() then return

        end if

    end while
end sub

Answer 1

You can probably do this by adding a parameter to the url string for the poster image. On roku, generate a timestamp and add it to the url.

dt=createobject("roDateTime") value=dt.AsSeconds() transferstringurl=transferstringurl+"?ts="+value.toStr()

ie - http://myservername.com/images/myposter.jpg?ts=1494302631

Or you could modify the headers - (not sure if it works from roku's client side, but it'd be something to set on the server side) Cache-Control: no-cache, no-store, must-revalidate Pragma: no-cache Expires: 0

You'd need to update the hdposterurl and sdposterurl for the item every time you want the poster to change, and you'll need to update all displayed content lists with the new data whether their screens are visible or not, to be sure it propagates the new image to everything (to be on the safe side) - or maybe you won't depending on how your code is set.

This actually solved my problem