Android Question call Sub From in Line java to B4a Class Module

david7374 · Sep 26, 2021

Hi everyone
in activity, it's easy to call sub from in Line java to b4a, for example

call sub from java to b4a in activity:

Sub Activity_Create(FirstTime As Boolean)
 
    Private jo           As JavaObject
    jo.InitializeContext
    jo.RunMethod("startPreview1",Null)

End Sub

Private Sub send_qv(s As String)
    Log(s)
End Sub

#if java
 
    public void startPreview1() {
        subQvEvent("send","Mohammad");
    }
 
    public void subQvEvent(String EventName,String values) {
 
         processBA.raiseEventFromUI(this, EventName.toLowerCase(BA.cul) + "_qv", values);
       
    }
 
#End If

but in b4aClass, I do not understand where the error comes from, here is my code

call sub from in Line java to b4a in b4aClass Module:

Public Sub Initialize
 
    Private jo           As JavaObject
    jo.InitializeNewInstance(Application.PackageName&".check.thisQv", Array(Null))
    jo.RunMethod("startPreview1",Null)

End Sub

Private Sub send_qv(s As String)
    Log(s)
End Sub
 

#if java

public class thisQv{

import anywheresoftware.b4a.BA;

public BA processBA;
public BA ba;


    public void startPreview1() {
        subQvEvent("send","Mohammad");
    }
 
    public void subQvEvent(String EventName,String values) {
 
         processBA.raiseEventFromUI(this, EventName.toLowerCase(BA.cul) + "_qv", values);
       
    }
 
}
#End If

and this error :

error:

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void anywheresoftware.b4a.BA.raiseEventFromUI(java.lang.Object, java.lang.String, java.lang.Object[])' on a null object reference

These are other codes that I tried and unfortunately got the same error.

call sub from java to b4a in b4aClass:

processBA.raiseEventFromUI(this, EventName.toLowerCase(BA.cul) + "_qv", values);

ba.raiseEvent(this,EventName.toLowerCase(BA.cul) + "_qv", values);

ba.raiseEvent(ba,EventName.toLowerCase(BA.cul) + "_qv", values);

ba.raiseEvent2(null, true, EventName.toLowerCase(BA.cul) + "_qv",false,values);

My main question is that, How call Sub From in Line java to B4a Class Module.
Thanks.

Erel · Sep 27, 2021

1. Don't waste your time with activities. Switch to B4XPages.
2.

B4X:

'in a B4XPages class:
Me.As(JavaObject).RunMethod("startPreview1", Null)

'in the java code:
getBA().raiseEventFromUI(...)

david7374 · Sep 27, 2021

Thanks Erel.
In fact, with your help, I learned how to call a function from Java to B4XPages.
But my main problem still persists. How to do it in standard class?
I use classes to categorize code as well as more scalability and readability.
Sometimes I need to use Java functions in classes. These functions may give us the output function after doing a series of tasks, which I need to use these values of this output function in b4a.
For example, when downloading a file, we have two functions, one is the download progress, the values of which are specified when downloading, and the other is called when the download is complete.

Progress Download and Complete:

#if java

protected void onProgressUpdate(String... progress) {
            // setting progress percentage
  }

protected void onProgressComplete() {
            
 }

#End if

If we want to use functions, we have to refer the values of these functions to b4a.
In B4XPages Class and activities it's ok. but standard class?
I have not yet found a solution to this issue in the standard class.

agraham · Sep 27, 2021

david7374 said:
How to do it in standard class?

Should be the same the same. B4XPages are standard class modules.

david7374 · Sep 27, 2021

agraham said:
B4XPages are standard class modules.

Thanks yeah, it was solved. I did not pay attention to this point at all,
Yes, exactly the problem was solved.
Thankful.

Here is my code:

call sub from in line java to b4a in b4aClass:

Public Sub Initialize
    
 
    Me.As(JavaObject).RunMethod("startPreview1", Null)

End Sub

Private Sub send_qv(s As String)
    Log(s)
End Sub
 

#if java

 
    public void startPreview1() {
        subQvEvent("send","Mohammad");
    }
    
    public void subQvEvent(String EventName,String values) {
    
        getBA().raiseEventFromUI(this, EventName.toLowerCase(BA.cul) + "_qv", values);
          
    }
    
#End If

Android Question call Sub From in Line java to B4a Class Module

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