ENVIBroadcastChannel

This is a reference to a broadcast channel object. You have two options to get a reference to this object:

Retrieve the ENVI system's broadcast channel using ENVI::GetBroadcastChannel.
Create a reference to a new broadcast channel to which you send messages and subscribe.

Example

This example demonstrates how all of the ENVI API messaging components work together. It simulates an analytic operation and updates its progress in a progress bar and in the IDL console.

PRO ProgressBarAbortExample

  COMPILE_OPT idl2

  ; Start the application

  e = ENVI()

  ; Get the broadcast channel to send messages to the ENVI system

  Channel = e.GetBroadcastChannel()

  ; Create an object that uniquely identifies the message.

  ; Use the ENVIAbortable object to check if progress

  ; was cancelled.

  Abort = ENVIAbortable()

  ; Broadcast a start message to the ENVI system

  Start = ENVIStartMessage('Progress Bar Title', Abort)

  Channel.Broadcast, Start

  ; Determine the number of steps to calculate

  ; percent complete for progress

  nSteps = 73

  ; Initialize progress

  Progress = ENVIProgressMessage('Executing Progress Message', $

    0, Abort)

  ; Iterate through the work

  FOR stepIndex=0, nSteps DO BEGIN

    ; Calculate progress for the step

    percentProgress = Round(stepIndex* 100.0/nSteps)

    ; Update progress percentage and broadcast the progress

    ; message to the ENVI system

    Progress.Percent = percentProgress

    Channel.Broadcast, Progress

    ; Check if aborted after sending progress to see if

    ; Abort_Requested was set by any listeners

    IF (Abort.Abort_Requested) THEN BREAK

    ; Simulate an analytic

    dataProcess = dist(1000)

    ; Print the step to see the abort working

    PRINT, stepIndex

  ENDFOR

  ; Broadcast a finish message to the ENVI system

  Finish = ENVIFinishMessage(Abort)

  Channel.Broadcast, Finish

END

Syntax

Result = ENVIBroadcastChannel([, ERROR=variable])

Methods

Broadcast

Unsubscribe

Keywords

ERROR (optional)

Set this keyword to a named variable that will contain any error message issued during execution of this routine. If no error occurs, the ERROR variable will be set to a null string (''). If an error occurs and the routine is a function, then the function result will be undefined.

When this keyword is not set and an error occurs, ENVI returns to the caller and execution halts. In this case, the error message is contained within !ERROR_STATE and can be caught using IDL's CATCH routine. See IDL Help for more information on !ERROR_STATE and CATCH.

See Manage Errors for more information on error handling in ENVI programming.

Version History

ENVI 5.3

Introduced

API Version

4.2