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:
B4X:
Dim j As HttpJob
j.Initialize("", Me)
j.Download("https://www.google.com")
Wait For (j) JobDone(j As HttpJob)
If j.Success Then
Log(j.GetString)
End If
j.ReleaseExample of downloading a quote from a quotes service:
B4X:
Sub DownloadQuote
Dim j As HttpJob
j.Initialize("", Me) 'name is empty as it is no longer needed
j.Download("http://quotesondesign.com/wp-json/posts?filter[orderby]=rand")
Wait For (j) JobDone(j As HttpJob)
If j.Success Then
'The result is a json string. We parse it and log the fields.
Dim jp As JSONParser
jp.Initialize(j.GetString)
Dim quotes As List = jp.NextArray
For Each quot As Map In quotes
Log("Title: " & quot.Get("title"))
Log("Content: " & quot.Get("content"))
Next
End If
j.Release
End SubNote that the HttpJob object is a local variable. This is the recommended way to create HttpJobs as it allows us to set the sender filter parameter (read more in the tutorial about resumable subs).
The same sub can be called multiple times and also other subs that send HttpJobs. As each HttpJob is unique, all the events will reach the correct place.
Downloading two resources, one after another:
B4X:
Sub DownloadTwoLinks
Dim j As HttpJob
j.Initialize("", Me) 'name is empty as it is no longer needed
j.Download("https://www.google.com")
Wait For (j) JobDone(j As HttpJob)
If j.Success Then
Log(j.GetString)
End If
j.Release
'second request
Dim j As HttpJob 'redim and initialize
j.Initialize("", Me)
j.Download("https://www.duckduckgo.com")
Wait For (j) JobDone(j As HttpJob)
If j.Success Then
Log(j.GetString)
End If
j.Release
End SubNow for a very common question. How to download a list of resources, one by one?
Simple:
B4X:
Sub Activity_Create(FirstTime As Boolean)
DownloadMany(Array("http://www.google.com", "http://duckduckgo.com", "http://bing.com"))
End Sub
Sub DownloadMany (links As List)
For Each link As String In links
Dim j As HttpJob
j.Initialize("", Me) 'name is empty as it is no longer needed
j.Download(link)
Wait For (j) JobDone(j As HttpJob)
If j.Success Then
Log("Current link: " & link)
Log(j.GetString)
End If
j.Release
Next
End SubA sub that downloads an image and sets it to an ImageView:
B4X:
Sub DownloadImage(Link As String, iv As ImageView)
Dim j As HttpJob
j.Initialize("", Me)
j.Download(Link)
Wait For (j) JobDone(j As HttpJob)
If j.Success Then
iv.Bitmap = j.GetBitmap
End If
j.Release
End SubExample of saving the downloaded file:
B4X:
Sub DownloadAndSaveFile (Link As String)
Dim j As HttpJob
j.Initialize("", Me)
j.Download(Link)
Wait For (j) JobDone(j As HttpJob)
If j.Success Then
Dim out As OutputStream = File.OpenOutput(File.DirInternal, "filename.dat", False)
File.Copy2(j.GetInputStream, out)
out.Close '<------ very important
End If
j.Release
End SubThe nice thing about this sub, and all above subs as well, is that they can be called multiple times:
B4X:
Sub Activity_Create(FirstTime As Boolean)
Activity.LoadLayout("1")
DownloadImage("https://b4x-4c17.kxcdn.com/android/forum/data/avatars/m/0/1.jpg?1469350209", ImageView1)
DownloadImage("https://b4x-4c17.kxcdn.com/images3/code.png", ImageView2)
End SubThe images will be downloaded concurrently.
Tip about the code flow: Sleep and Wait For are equivalent to calling Return from the calling sub perspective.
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