Android Question How to flag 404 "page not found" ? [solved]

trepdas · Jan 16, 2021

Hello good people,

I need to get a boolean true or false for page 404 (page not found) . (such as http://nonexistingdomain.com/342.html)

what would be the best method to do this?

I am trying to use the example here with no success :

WebView Error 404 or ERR_ADDRESS_UNREACHABLE

Hello, I would like to intercept error 404 or ERR_ADDRESS_UNREACHABLE when using the webview, I do not know how to do it, I looked in the forum and I followed the several examples But none worked so I would like to know if someone can please help me, my code is simple: #Region Project...

www.b4x.com

when I call the check_http sub and go step by step in debugger mode, it seems that it skips the Sub JobDone completely.

B4X:

Sub check_http
    
    Dim job1 As HttpJob
    job1.Initialize("Job1", Me)
'    'Send a GET request
    job1.Download(WebAddress)
End Sub
'
Sub JobDone (job As HttpJob)
    Log("JobName = " & job.JobName & ", Success = " & job.Success)
    If job.Success = False Then
        Log("Error: " & job.ErrorMessage)
        'do something else
        Msgbox ("error.","")
    
    Else
        Log(job.GetString)
        'do something if ok
    
        WebView1.LoadUrl(WebAddress)
    End If
    job.Release
End Sub

help as usual will be very appreciated.

mc73 · Jan 16, 2021

Try using a WaitFor.

trepdas · Jan 16, 2021

Thank you so much for the quick reply, mc73

I tried the simple example shown here :

[B4X] OkHttpUtils2 with Wait For

Downloading resources is simpler with the new Resumable Subs feature. Using Wait For we can wait for the JobDone event in the same sub that started the download. No longer is it needed to have a single sub that handles all requests results. Simplest example: Dim j As HttpJob j.Initialize(""...

www.b4x.com

it is not working. from a reason while debugging it skips the wait for and continue executing code

B4X:

Sub check_http
    Dim j As HttpJob
    j.Initialize("", Me)
    j.Download(WebAddress)
    Wait For (j) JobDone(j As HttpJob)
    If j.Success Then
        Log(j.GetString)
    End If
    j.Release


End Sub

mc73 · Jan 16, 2021

Sure it's skipped? Try this one:

B4X:

Sub check_http
    Dim j As HttpJob
    j.Initialize("", Me)
    j.Download(WebAddress)
    Wait For (j) JobDone(j As HttpJob)
    If j.Success Then
        Log(j.GetString)
    else
       log(j.errorMessage):' your error should be here
   End If
   j.Release
End Sub

trepdas · Jan 16, 2021

yes, I just copied it from you as is. it still skips. it gets to wait for and skips the if j.success (exiting sub)

mc73 · Jan 16, 2021

Can you please post your check_http sub?

trepdas · Jan 16, 2021

attaching, including the uncomment block from previous try...

B4X:

Sub check_http
    
    Dim j As HttpJob
    j.Initialize("", Me)
    j.Download(WebAddress)
    Wait For (j) JobDone(j As HttpJob)
    If j.Success Then
        Log(j.GetString)
    Else
       Log(j.errorMessage):' your error should be here
   End If
    j.Release
  
    '    Dim job1 As HttpJob
'    job1.Initialize("Job1", Me)
    ''    'Send a GET request
'    job1.Download(WebAddress)
'    Wait For (job1) JobDone(job1 As HttpJob)

    'Sub JobDone (job As HttpJob)
'    Log("JobName = " & job.JobName & ", Success = " & job.Success)
'    If job.Success = False Then
'        Log("Error: " & job.ErrorMessage)
'        'do something else
'        Msgbox ("error.","")
    '
'    Else
'        Log(job.GetString)
'        'do something if ok
    '
'        WebView1.LoadUrl(WebAddress)
'    End If
'    job.Release
    'End Sub
  
  
  
End Sub

mc73 · Jan 16, 2021

Is your WebAddress set somewhere? Or just empty?

trepdas · Jan 16, 2021

Webaddress is set as public string in the code.
and contain a url that is deliberately inaccessible (404)

mc73 · Jan 16, 2021

Are you calling check_http from inside activity_create? Perhaps you can upload a small project showing the problem which users here can test.

trepdas · Jan 16, 2021

err.no.

I call it from a sub that is triggered from a button click.

I will need this to execute upon user's click (url availability check)

mcqueccu · Jan 16, 2021

You can check the status code in the header. It will return 200+,300+,400+

so if you get your 404 then you know the page does not exist

trepdas · Jan 17, 2021

mcqueccu said:
You can check the status code in the header. It will return 200+,300+,400+

so if you get your 404 then you know the page does not exist

how do I check this with webview?

Erel · Jan 17, 2021

WebView??????????

You should of course use OkHttpUtils2 and only with Wait For.

You can check the status code with Job.Response.StatusCode.

trepdas · Jan 17, 2021

ok.
it was easy to understand > no webview.
I deleted the webview component.

as for the problem - it persist.

I need this action when a text box is filled by the user and a button is clicked.
the user's string is being converted to a url and then I need to check if 404.

so from the button_click I call a new sub (go) and that sub calls the check_http.(as shown above in the picture)
but it won't work.

it goes until the "wait for" and then skips on to execute the above sub.

what am I missing?
?

Erel · Jan 17, 2021

trepdas said:
what am I missing?

Long answer: watch the resumable subs video tutorial: https://www.b4x.com/etp.html

Short answer: [B4X] Resumable subs that return values (ResumableSub)

trepdas · Jan 17, 2021

Thank you. gonna learn some more...
?

trepdas · Jan 18, 2021

I am trying the exact example from the resumable subs video (video time : 24:35)
I want to continue executing code only after the check for the 404 is done. but still with no success. ??

once it gets to the wait for (inside the check sub) - it goes somewhere without getting to the if statement.
I do get the message "*** Service (httputils2service) Create ***" in the log.

am I that stupid? (probably)
should I quit programming? (no)

can anyone post a simple and fast code to check 404 ??

(Webaddress is public string and already contain a url)

B4X:

Sub Go


    CheckInternal
    ReplaceSpaces
    CreateIDN

    Wait For (CheckHttp(WebAddress)) complete (Result As Boolean)
    ' is it 404 ??


    If LN<3 Then
        InternalFeatures
    End If

End Sub

B4X:

Sub CheckHttp (url As String) As ResumableSub
    Dim job As HttpJob
    job.Initialize("", Me)
    job.Download(url)
    Wait For (job) JobDone(job As HttpJob)

    If job.Success Then
        Log(job.GetString)
    Else
       Log(job.errorMessage):' your error should be here
   End If
    job.Release
      Return job.Success
End Sub

Erel · Jan 18, 2021

1. Please don't make duplicate posts.
2. This code is correct. I guess that you expect other code not to run. This will not be the case as the main thread is never paused.

Line #9 will only run after CheckHttp completed.

trepdas · Jan 18, 2021

Thank you. I still can't make it work (((

once it gets to line 'Wait For (job) JobDone(job As HttpJob)'
I get in the log a message "*** Service (httputils2service) Create ***"
but...nothing happens.
the log in sub 'Go' (line 5) is not being executed

B4X:

Sub Go

    Wait For (CheckHttp(WebAddress)) complete (flag As Boolean)
    ' is it 404 ??
    Log ("why this line is not being executed?")
   

    If LN<3 Then
        InternalFeatures
    End If
   
End Sub

B4X:

Sub CheckHttp (url As String) As ResumableSub  
    Dim job As HttpJob
    job.Initialize("", Me)
    job.Download(url)
    Wait For (job) JobDone(job As HttpJob)

If job.Success Then
        Log(job.GetString)
    Else
       Log(job.errorMessage):' your error should be here
   End If
    job.Release
      Return job.Success
End Sub

Android Question How to flag 404 "page not found" ? [solved]

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