Android Question [Solved] Webview CaptureBitmap error

[hung]

I created a webview wv_img and loadurl to fill the conentent with some tables, and images.
Then do wv_img.CaptureBitmap to a bitmap. But this randomly failed.

    Dim lbmp As Bitmap, lbok As Boolean

    lbok = False
    Dim cnt As Int
    For cnt = 0 To 50
        If lbok = False Then
            lbok = True
            wv_img.Invalidate
            Try
                lbmp = wv_img.CaptureBitmap
            Catch
                lbok = False
                Log("capturebitmap failed")
            End Try   
        End If
    Next

I suspected the wv_img.loadurl is slow then tried to wait until it is finished. But the event triggered far before it finish loading, i.e. immediate said "load url ok".

Private wv_img As WebView

wv_img.LoadUrl(....)   
Wait For wv_img_PageFinished (url As String)
    Log("wv_img load url ok")

How could I wait for the page finish loading?

 

[drgottjr]

this:

Dim lbmp As Bitmap, lbok As Boolean

lbok = False
Dim cnt As Int
For cnt = 0 To 50
If lbok = False Then
lbok = True
wv_img.Invalidate
Try
lbmp = wv_img.CaptureBitmap
Catch
lbok = False
Log("capturebitmap failed")
End Try
End If
Next

needs to be destroyed immediately. i suggest fire.

although waiting for page load can usually solve a lot of problems, it depends on what is being loaded. for example, if a webpage runs a command to load another page or to perform some operation, page load only refers to the first webpage. the second load or the operation to be carried out are not covered. do you understand? it's like starting an automobile and then driving somewhere. starting the automobile = page load. driving somewhere = .....
you may need to wait for something else.
you might want to post the project.

 

[hung]

this:

Dim lbmp As Bitmap, lbok As Boolean

lbok = False
Dim cnt As Int
For cnt = 0 To 50
If lbok = False Then
lbok = True
wv_img.Invalidate
Try
lbmp = wv_img.CaptureBitmap
Catch
lbok = False
Log("capturebitmap failed")
End Try
End If
Next

needs to be destroyed immediately. i suggest fire.

although waiting for page load can usually solve a lot of problems, it depends on what is being loaded. for example, if a webpage runs a command to load another page or to perform some operation, page load only refers to the first webpage. the second load or the operation to be carried out are not covered. do you understand? it's like starting an automobile and then driving somewhere. starting the automobile = page load. driving somewhere = .....
you may need to wait for something else.
you might want to post the project.

The original program does one CaptureBitmap then found many time failure and stop my program.

The loop was to re-try CaptureBitmap with the hope with one time success. It helps many cases but there are still cases 50 retries failed.

The project has many parts. The above two codes describe the current problems. Thanks.

 

[hung]

this:

Dim lbmp As Bitmap, lbok As Boolean

lbok = False
Dim cnt As Int
For cnt = 0 To 50
If lbok = False Then
lbok = True
wv_img.Invalidate
Try
lbmp = wv_img.CaptureBitmap
Catch
lbok = False
Log("capturebitmap failed")
End Try
End If
Next

needs to be destroyed immediately. i suggest fire.

although waiting for page load can usually solve a lot of problems, it depends on what is being loaded. for example, if a webpage runs a command to load another page or to perform some operation, page load only refers to the first webpage. the second load or the operation to be carried out are not covered. do you understand? it's like starting an automobile and then driving somewhere. starting the automobile = page load. driving somewhere = .....
you may need to wait for something else.
you might want to post the project.

Understand about the page loading. It is exactly the cases so the Finished does not reflect the true, or in this case, it does not help.

 

[drgottjr]

webview i/o is async. waiting loops will get you into trouble. especially if you are waiting for the wrong thing. what your project does exactly is not completely clear. it will be difficult for us to help. you are not the first person with a project that has many parts. i suspect that not all those parts relate to determining when the page is ready to be captured as a bitmap. page finished is not the only way a webview can communicate with you. in the end, there may be no solution, but providing little information does not lead to a solution.

 

[hung]

I created a webview wv_img and loadurl to fill the conentent with some tables, and images.
Then do wv_img.CaptureBitmap to a bitmap. But this randomly failed.

    Dim lbmp As Bitmap, lbok As Boolean

    lbok = False
    Dim cnt As Int
    For cnt = 0 To 50
        If lbok = False Then
            lbok = True
            wv_img.Invalidate
            Try
                lbmp = wv_img.CaptureBitmap
            Catch
                lbok = False
                Log("capturebitmap failed")
            End Try  
        End If
    Next

I suspected the wv_img.loadurl is slow then tried to wait until it is finished. But the event triggered far before it finish loading, i.e. immediate said "load url ok".

Private wv_img As WebView

wv_img.LoadUrl(....)  
Wait For wv_img_PageFinished (url As String)
    Log("wv_img load url ok")

How could I wait for the page finish loading?

Seems solved with this old solution from previous reply from Erel. I put he code in Activity first time. The random blank capturebitmap did not happen for close to one day. So I consider this is (hopefully) solved.

Sub EnableSlowWebViewDocumentDraw
   Dim p As Phone
   If p.SdkVersion >= 21 Then
     Dim jo As JavaObject
     jo.InitializeStatic("android.webkit.WebView").RunMethod("enableSlowWholeDocumentDraw", Null)
   End If
End Sub