B4J Question WebViews on Pi

[Jon Eskdale]

Please - is it possible to use a WebView on a Pi with B4J
I've my proof of concept working for a UI interfaced to the Serial port now
Next stage was the WebView which I thought would be the easy bit. I can get the Proof of Concept working in B4J on the PC but it doesn't work on the Pi

When you start the program on the Pi

Program started.
java.lang.reflect.InvocationTargetException
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:566)

The full error can be seen here if it helps
https://pastebin.com/BKX8ds3g
It's not a very helpful message to me at least.

This happens when the loadlayout is executed
I have a working program that runs on B4J on the PC but this is the simplest sample I could produce which has the error see tryVW.zip attached

B4J is version 7.00 and the Java on the Pi is BellSoft Liberica is a build of OpenJDK 11.0.1

Thanks - Jon

 

[Daestrum]

from the Bellsoft website

JavaFX for the Raspberry Pi

Liberica JDK 11 come with a bundled JavaFX implementation which is based on OpenJFX. The following tables lists Java FX modules status of Liberica distribution

■ Java FX Graphics - works.

■ Java FX Controls - works.

■ Java FX Media - does not work.

■ Java FX Webkit - does not work.

 

[Jon Eskdale]

Thanks Daestrum - So
Is there a different Java implementation that I should use?
Some other solution?

Or do I have to forget about using B4J on the Pi and find some other language to use?

Thanks Jon

 

[Erel]

I don't think that there is any Java implementation available for RPi that supports WebView.

Or do I have to forget about using B4J on the Pi and find some other language to use?

It depends on what you are trying to do...

 

[Jon Eskdale]

Thanks Erel - The Project - A Fiend of mine has a small company designing and manufacturing Industrial Terminals. www.industrialdataproducts.co.uk I have written some software for him in the past. He now has a new terminal which is based on a Raspberry Pi and the touch screen together with a custom IO board housed in an industrial housing suitable for use on the Factory floor (This new terminal is not shown on the website yet). But a really nice industrial product. Typically this terminal is wired to a production machine and counts the units made and the production rate etc. The custom IO board communicates with the pi using the serial port. The Pi is networked via ethernet and is responsible for transferring the data from the Custom IO board to the Main server and vice versa for remote control It also displays status from the server as a web page (Kiosk mode) - hence the need for a webview. If there is a problem on the production machine the terminal is used by an operator via the touch screen to send the status (e.g. Stopped waiting for raw material, Stopped due to machine failure, Stopped due to material jam ....) As I've used B4A and B4i in the past and saw B4J was now available for the Pi, I suggested that we should write something in B4J so as to create a solution which would allow quick customisation of the product.
I have written him an Engineering screen as an example which communicates with the custom IO board and displays the information in B4J and this was well received. I then tried to write a demo webview not realising this would be an issue. He also has some Terminals with larger screens 15 inch but otherwise similar in production.

I've done some work with Pi's in the past but not a lot, Primarily I'm a Windows / Microcontroller programmer with hardware design experience.
Do I try and mix languages/solutions or any ideas Would like to keep the B4J
Thanks Jon

 

[Erel]

If the web page is not too complicated then you can download it with jOkHttpUtils2 and show it with a native UI.

 

[xulihang]

I think one solution is to make a server app and open the website on local browser and use websocket or ajax to update the webpage.

 

[Jon Eskdale]

Thanks Erel - but don't think that would work as the web page is dynamically updated as the production changes and I wouldn't know when to download it.
I wonder if the Liberica JDK 11 will ever support the webkit on Pi or if they have no intention of looking at it.
Would it be possible to have a WebView running as a separate app and have B4J control whether the Webview is displayed or if B4J screen is displayed?
The plan was to have a 3-second press on the Webview to switch to the B4J main screen and then a button on the main B4J screen to switch back to the Webview.
I had that working in B4J on the PC but it won't work on the Pi. Is that something B4J could do?
Thanks Jon

 

[Erel]

Would it be possible to have a WebView running as a separate app

Not sure what you mean with WebView here. WebView in the context of B4J is a JavaFX embedded browser engine. It is not available in the RPi Java runtime.

 

[Jon Eskdale]

Thanks Erel - what I mean is a kiosk type browser something like this https://www.raspberrypi.org/forums/viewtopic.php?t=146729 in kiosk mode although I've not tried this one yet. I would need to have something like that running and have the ability to switch between it and the B4J screen. The Webview would have been ideal if it had worked.

 

[Michael1968]

I think one solution could be Android things
You can write the programm with b4a

 

[Michael1968]

Hi Jon

I have make a quick test with my raspberrypi 3B with the official 7" Display.

-> latest image (1.0.8) on 4 Gb SD-Card
-> webview work
-> all testet xui example work

 

[Jon Eskdale]

Hi Michael - That sounds extremely interesting.
Could you confirm what you mean by latest image 1.0.8
I have the latest Raspbian-stretch-full installed
and B4J 7.00
I've installed the Java bellsoft-jdk11.0.1-linux-arm32-vfp-hflt-lite.tar.gz
Could you confirm what java you are using

Many Thanks - Jon

 

[Michael1968]

Hi Jon..

AndroidThings is a different platform.

a good starting point is:

https://www.b4x.com/android/forum/threads/android-things-getting-started.74821/#content
https://developer.android.com/things/

... and there are examples in the forum

Michael

 

[Jon Eskdale]

Hi Michael, Thanks - I did some reading on the Android Things and it appears Google classify the Pi as Development only - not approved for production. Which would cause problems selling the Android things concept to some customers I think. It also says that it only supports the MicroSD card. We are running the pi from an SSD connected via a USB adapter as we had too many failures of SD card in use. Its a few pounds extra but the reliability pays for itself. Still looking for/working on a solution - Thanks