Visual FoxPro

Cancel Async Task if not Completed after a Max Time

See more Async Examples

Demonstrates how to wait a maximum amount of time for an asynchronous task to completed. If not completed in the allotted amount of time, the task is cancelled. Visual FoxPro

LOCAL lnSuccess
LOCAL loHttp
LOCAL lnWaitMaxMs
LOCAL lcDownloadUrl
LOCAL loTask
LOCAL lnWasCanceled

lnSuccess = 0

* This example requires the Chilkat API to have been previously unlocked.
* See Global Unlock Sample for sample code.

loHttp = CreateObject('Chilkat.Http')

* Set some timeouts, in seconds:
loHttp.ConnectTimeout = 15
loHttp.ReadTimeout = 15

* Wait a max time of 2 seconds for the task.
* In this example, it's an unreasonably small amount of time,
* which means the task will get cancelled.
lnWaitMaxMs = 2000

* We're just going to download for 2 seconds and then cancel.
* Substitute your own URL with a large enough file for testing..
lcDownloadUrl = "http://download.mono-project.com/archive/4.6.1/windows-installer/mono-4.6.1.5-gtksharp-2.12.38-win32-0.msi"

loTask = loHttp.DownloadAsync(lcDownloadUrl,"qa_output/mono.msi")
loTask.Run()

* Wait a maximum of waitMaxMs for the task (i.e. the HTTP download) to complete.
* The Wait method returns when the task has been canceled, aborted, or completed, or when the max allotted time has passed.
loTask.Wait(lnWaitMaxMs)

* At this point, the download may or may not have completed.  
* Rather than checking the Task status, we can call task.Cancel because
* if the Task is no longer running (because it already completed, was canceled or aborted), then the 
* call to Cancel is a NO-OP (meaning it does nothing and the Task's status is unaffected).
* Also, task.Cancel returns 1 if the task was in the "queued" or "running" state and was canceled or aborted. 
* The method returns 0 if the task has any other status.
lnWasCanceled = loTask.Cancel()
IF (lnWasCanceled = 1) THEN
    ? "The HTTP download took too long and was canceled."
ELSE
    * Find out what happened.
    IF (loTask.StatusInt = 7) THEN
        * The task completed, which means the background thread's call to Download completed
        * with success or failure.  Find out which...
        lnSuccess = loTask.GetResultBool()
        IF (lnSuccess = 1) THEN
            ? "Download successful!"
        ELSE
            ? "Download failed prior to waitMaxMs..."
            ? loTask.ResultErrorText
        ENDIF

    ELSE
        * The task must've been canceled or aborted by some other means..
        ? "Task did not complete.  Final status: " + loTask.Status
    ENDIF

ENDIF

RELEASE loTask

RELEASE loHttp