PowerBuilder

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. PowerBuilder

integer li_rc
integer li_Success
oleobject loo_Http
integer li_WaitMaxMs
string ls_DownloadUrl
oleobject loo_Task
integer li_WasCanceled

li_Success = 0

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

loo_Http = create oleobject
li_rc = loo_Http.ConnectToNewObject("Chilkat.Http")
if li_rc < 0 then
    destroy loo_Http
    MessageBox("Error","Connecting to COM object failed")
    return
end if

// Set some timeouts, in seconds:
loo_Http.ConnectTimeout = 15
loo_Http.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.
li_WaitMaxMs = 2000

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

loo_Task = loo_Http.DownloadAsync(ls_DownloadUrl,"qa_output/mono.msi")
loo_Task.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.
loo_Task.Wait(li_WaitMaxMs)

// 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.
li_WasCanceled = loo_Task.Cancel()
if li_WasCanceled = 1 then
    Write-Debug "The HTTP download took too long and was canceled."
else
    // Find out what happened.
    if loo_Task.StatusInt = 7 then
        // The task completed, which means the background thread's call to Download completed
        // with success or failure.  Find out which...
        li_Success = loo_Task.GetResultBool()
        if li_Success = 1 then
            Write-Debug "Download successful!"
        else
            Write-Debug "Download failed prior to waitMaxMs..."
            Write-Debug loo_Task.ResultErrorText
        end if

    else
        // The task must've been canceled or aborted by some other means..
        Write-Debug "Task did not complete.  Final status: " + loo_Task.Status
    end if

end if

destroy loo_Task


destroy loo_Http