Create a dialog box that exits only when ok is clicked in roku

how to create a dialog box in roku that opens when back button on remote is clicked. when ok option is selected on dialog box app exits. this is the code in main.brs

sub Main()
    ShowChannelRSGScreen()
end sub

sub ShowChannelRSGScreen()
    ' The roSGScreen object is a SceneGraph canvas that displays the contents of a Scene node instance
    screen = CreateObject("roSGScreen")
    ' message port is the place where events are sent
    m.port = CreateObject("roMessagePort")
    ' sets the message port which will be used for events from the screen
    screen.SetMessagePort(m.port)
    ' every screen object must have a Scene node, or a node that derives from the Scene node
    scene = screen.CreateScene("MainScene")
    screen.Show() ' Init method in MainScene.brs is invoked

    ' event loop
    while(true)
        ' waiting for events from screen
        msg = wait(0, m.port)
        msgType = type(msg)
        if msgType = "roSGScreenEvent"
            if msg.IsScreenClosed() then return
        end if
    end while
end sub

i tried the above code but i dont know how to create an exit box dialog.

Solution

You can utilize roku's StandardMessageDialog for this. In summary:

make a new StandardMessageDialog
set some props on it, register a callback, then show it
when the user clicks a button, handle the logic accordingly

Here's your code, updated to show how this works:

MainScene.brs

sub init()
end sub

function onKeyEvent(key as string, press as boolean) as boolean
  if press and key = "back" then
    'create the dialog
    dialog = createObject("roSGNode", "StandardMessageDialog")
    '.message is an array of messages
    dialog.message = ["Do you really want to exit?"]
    dialog.buttons = ["Yes", "No"]
    'register a callback function for when a user clicks a button
    dialog.observeFieldScoped("buttonSelected", "onDialogButtonClick")

    'assigning the dialog to m.top.dialog will "show" the dialog
    m.top.dialog = dialog
    return true
  end if
end function

function onDialogButtonClick(evt)
  buttonIndex = evt.getData()
  'did the user click "Yes"
  if buttonIndex = 0 then
    'set appExit which will kill the channel in the main loop
    m.top.appExit = true

  'user clicked "no"
  else
      'close the dialog
      m.top.dialog.close = true
      return true
  end if
end function

MainScene.xml

<?xml version="1.0" encoding="utf-8" ?>
<component name="MainScene" extends="Scene">
  <script type="text/brightscript" uri="MainScene.brs" />
  <interface>
    <field id="appExit" type="bool" alwaysnotify="true" value="false"/>
  </interface>
</component>

pkg:/source/main.brs

sub Main()
  ShowChannelRSGScreen()
end sub

sub ShowChannelRSGScreen()
  ' The roSGScreen object is a SceneGraph canvas that displays the contents of a Scene node instance
  screen = CreateObject("roSGScreen")
  ' message port is the place where events are sent
  m.port = CreateObject("roMessagePort")
  ' sets the message port which will be used for events from the screen
  screen.SetMessagePort(m.port)
  ' every screen object must have a Scene node, or a node that derives from the Scene node
  scene = screen.CreateScene("MainScene")
  screen.Show() ' Init method in MainScene.brs is invoked
  'observe the appExit event to know when to kill the channel
  scene.observeField("appExit", m.port)
  'focus the scene so it can respond to key events
  scene.setFocus(true)


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

    if msgType = "roSGScreenEvent" then
      if msg.isScreenClosed() then
        return
      end if
    'respond to the appExit field on MainScene
    else if msgType = "roSGNodeEvent" then
      field = msg.getField()
      'if the scene's appExit field was changed in any way, exit the channel
      if field = "appExit" then
        return
      end if
    end if
  end while
end sub