PrintHtml is a Windows utility that prints html files. You can see more information about it here: http://www.b4x.com/android/forum/threads/print-with-printhtml-tool.35492/
In this example we use it to print messages from the device. The device sends a POST request with the html message and the PrintServer uses jShell to call PrintHtml and print the message.
The client code is trivial:
The server code is more interesting. We want the server to handle requests one after another. There are no advantages for sending multiple printer jobs and it is also not clear whether PrintHtml and the printer driver support concurrent jobs.
This is done by setting the SingleThreaded parameter to True:
jShell library runs the task in the background and raises the ProcessCompleted event when the task completes. This means that we need to pause the current request until the task completes and then resume it. Otherwise the Handle sub will be completed before the task completes. The response is committed when the execution of Handle completes.
This is done by calling StartMessageLoop in the Handle sub and then StopMessageLoop in js_ProcessCompleted sub:
In this example we use it to print messages from the device. The device sends a POST request with the html message and the PrintServer uses jShell to call PrintHtml and print the message.
The client code is trivial:
B4X:
Sub Process_Globals
Private link As String = "http://192.168.0.100:51042/print"
End Sub
Sub Activity_Create(FirstTime As Boolean)
End Sub
Sub Activity_Click
Dim j As HttpJob
j.Initialize("j", Me)
j.PostString(link, "This is a test message sent from the device...")
End Sub
Sub JobDone(j As HttpJob)
If j.Success Then
Log("Success: " & j.GetString)
Else
Log("Error: " & j.ErrorMessage)
End If
j.Release
End SubThe server code is more interesting. We want the server to handle requests one after another. There are no advantages for sending multiple printer jobs and it is also not clear whether PrintHtml and the printer driver support concurrent jobs.
This is done by setting the SingleThreaded parameter to True:
B4X:
Sub Process_Globals
Private srvr As Server
End Sub
Sub AppStart (Args() As String)
srvr.Initialize("")
srvr.Port = 51042
srvr.AddHandler("/print", "Print", True) 'SingleThreaded = True
srvr.Start
StartMessageLoop
End SubjShell library runs the task in the background and raises the ProcessCompleted event when the task completes. This means that we need to pause the current request until the task completes and then resume it. Otherwise the Handle sub will be completed before the task completes. The response is committed when the execution of Handle completes.
This is done by calling StartMessageLoop in the Handle sub and then StopMessageLoop in js_ProcessCompleted sub:
B4X:
Sub Class_Globals
Private js As Shell
Private mresp As ServletResponse
End Sub
Public Sub Initialize
End Sub
Sub Handle(req As ServletRequest, resp As ServletResponse)
mresp = resp
'save the request to a file
Dim out As OutputStream = File.OpenOutput(File.DirApp, "temp.txt", False)
File.Copy2(req.InputStream, out)
out.Close
Dim params As List
params.Initialize
'optionally set the printer
'params.Add("printername=novapdf")
params.Add("file=temp.txt")
js.Initialize("js", "printhtml.exe", params)
js.WorkingDirectory = File.DirApp
js.Run(-1)
StartMessageLoop '<--- wait for the event
End Sub
Sub js_ProcessCompleted (Success As Boolean, ExitCode As Int, StdOut As String, StdErr As String)
Log("Success=" & Success & ", StdOut=" & StdOut & ", StdErr=" & StdErr)
If Success Then
mresp.Write("Message was printed successfully.")
Else
mresp.SendError(500, StdErr)
End If
StopMessageLoop '<-- close the secondary message loop
End Sub
BIG THANKS.
