Android Question Local HTML page does not show pictures

[MitchBu]

I display local html file in a WebView. It works, but the pictures in the html page do not show. They are coded to be next to the html page, and I verified the pictures files are indeed there, as expected.

Example code. Nothing unusual or fancy :

<img src="buttonpopup.png" align="BOTTOM" border="0" width="20">

What could be preventing them to display ?

 

[warwound]

<img src="buttonpopup.png" align="BOTTOM" border="0" width="20">

Try modifying the src path so the WebView knows exactly where your image file is located:

<img src="file:///android_asset/buttonpopup.png" align="BOTTOM" border="0" width="20">

That assumes your image file is not in a sub-directory of your files folder.

 

[MitchBu]

Yes, indeed, I came to believe I need to use an absolute path. But path will not be the same in debug as in release. I had hoped by putting the picture file next to the HTML page it would work in relative.

I will try to embed the picture as Base64.

Thanks warwound. BTW congratulations for WebViewExtras.

 

[warwound]

Is this thread of use: https://www.b4x.com/android/forum/t...debug-rapid-”-b4a-3-50-version.38981/#content ?

 

[MitchBu]

Is this thread of use: https://www.b4x.com/android/forum/threads/images-loaded-in-webviews-are-not-displayed-in-mode-“debug-rapid-”-b4a-3-50-version.38981/#content ?

Yes, you are right. I already use WebViewAssetFile to get the html file.

Embedding an image in the HTML code does work, but since I need it many times in an HTML table for buttons, I am now going to try WebView.LoadHTML and place the URL to the file at run time, so I can place the proper absolute path.

 

[MitchBu]

Follow-up :

Now I load the html page into a variable, so I can replace the picture file name by a full absolute path.

It works very nicely, but the HTML page load time is not negligible, about one second, and that feels strange.

Is there any way I can place this data in a constant in a separate module somewhere, so I don't mess up Globals ?

Otherwise I thought about placing that into a sub that returns it, placed at the very end of the code.


.

 

[warwound]

That one second load time might be the WebView being slow to render your HTML, or it might be your b4a code building the large HTML string.
Are you using a StringBuilder to build your HTML string or string concatenation?
Try a Stringbuilder and see if that improves the time taken to create your HTML string.

 

[MitchBu]

Yes, it could be concatenation when I read the file line by line. I could not locate a method to read everything at one with TextReader.

I will learn StringBuilder.

Thank you Martin.

 

[MitchBu]

That was it. Using TextReader .ReadAll, the page loads instantly

 

[Erel]

That was it. Using TextReader .ReadAll, the page loads instantly

Note that there is almost never a good reason to use TextReader (or TextWriter).
Use File.ReadString instead.

Dim s As String = File.ReadString(...)

 

[MitchBu]

I replaced TextReader in my code. Very nice to use only one sentence instead of several lines.

Thank you Erel

 

[MitchBu]

I know this is an old thread, but I picked up from there in my development course.

In short, html src with ".unpacked" in the picture name would not work. No dice. So I could not use picture files from assets. Strangely enough, I could loadURL the picture file, but if it was inside a page, it would not display.

My solution was to use base64 encoded pictures in the HTML source.

Here is the page that describes the technique:

How to Embed an Image to Get a Self-Contained Web Page (thesitewizard.com)

How to embed an image into an HTML file so that you have a self-contained web page

www.thesitewizard.com

I use Bluegriffon to edit and compose my HTML page. It is a free WYSIWYG HTML editor, which displays base64 encoded pictures just fine:

http://bluegriffon.org/

Hope this will be of use fo others bumping into the same issue.