Exiting out of a Brightscript SceneGraph application

To exit a a SceneGraph application you have to complete executions of your main method. A nice easy way to do this is to observe a field on your scene and then fire a roSGNodeEvent via the port (Once you’ve read this you can download a full working app that demonstrates the below here. It’s pretty sweet).

You’ve probably got something like the following in your main app brs file.

screen = CreateObject("roSGScreen")
m.port = CreateObject("roMessagePort")
screen.setMessagePort(m.port)
scene = screen.CreateScene("mainScene")
screen.show()
scene.setFocus(true)

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

  if msgType = "roSGScreenEvent" then
    if msg.isScreenClosed() then
      return
    end if
  end if
end while

This would exit out if you clicked back on the RCU when the scene is focused as msg.isScreenClosed() would be true - but what if we wanted to close the app on another event? It’s actually pretty simple to do. The main challenge is exiting out of the while loop. A handy way is to add an observer to the scene and pass the port as the handler.

You could modify this main screen to look something like:

screen = CreateObject("roSGScreen")
m.port = CreateObject("roMessagePort")
screen.setMessagePort(m.port)
scene = screen.CreateScene("mainScene")
screen.show()
scene.observeField("exitApp", m.port)
scene.setFocus(true)

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

  if msgType = "roSGScreenEvent" then
    if msg.isScreenClosed() then
      return
    else if msgType = "roSGNodeEvent" then
      field = msg.getField()
      if field = "exitApp" then
        return
      end if
    end if
  end if
end while

By adding the observer scene.observeField("exitApp", m.port) on the scene a roSGNodeEvent msg will fire on m.port when we change the exitApp interface field. It’s a nice succinct way of handling this.

Set up your MainScene.xml so it has an observable interface boolean field called exitApp or similar:

<?xml version="1.0" encoding="utf-8" ?>

<component name="MainScene" extends="OverhangPanelSetScene" >
    <interface>
        <field id="exitApp" type="boolean" value="false" />
    </interface>

    <children>

    </children>
    <script type="text/brightscript" uri="pkg://components/MainScene.brs" />
</component>

Then you need to setup your MainScene.brs to alter the exitApp variable on an OK click:

function init() as Void
    print "ExitApp"
end function

function onKeyEvent(key as String, press as Boolean) as Boolean
    if key = "OK" then
        m.top.exitApp = true
    end if
end function

Download the source for this here.

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