B4A Class Continuous knob

Hello.
I searched the forum and gave it a long thought (actually closed this -posting- window several times throughout the past weeks) but haven't managed to figure it out.

I'm trying to create a continuous rotary knob. It should return something like 1 when you rotate it to the right and -1 when you do the same, but to the left this time.

Everything I've seen has min-max values. And when you would reach the max value it would reset to the min, thus interrupting the seeking process in a disturbing fashion.

If anybody has a good solution, would you kindly point me in the right direction?

Thank you!

 

[Erel]

The attached project should help you get started:

 

[pauleffect]

You did this for me?

I'm... very grateful and impressed. Thank you a lot!

 

[Erel]

For you... and for any developer who like to implement such a view.

 

[Informatix]

Did you look at the knobs provided at the end of my tutorial?

 

[Informatix]

By testing my old code for knobs, I noticed that it did not work with the obfuscation mode. This is now fixed.

 

[pauleffect]

I was just thinking about you, @Informatix.

Specifically, the bitmap plus library.

I'm trying to use Erel's code with bitmap plus. Once I'm satisfied with the outcome, I'll post the results.

Thank you both for your time.

 

[Manuel Moreno-Eguilaz]

Hi Erel,

Thank you very much for your attached project.

Is it possible to pass some parameters to the knob object when calling Initialize function?

I would like to limitate the minimum and maximum values in one Knob by passing these values in the creation process of the object.

Thank you. I love B4A.

Manuel

 

[Erel]

Yes. You can add parameters to the initialize sub.

 

[DT1111]

Hi Erel

Thanks for the Knob example and I have modified the pnl_Touch sub so that the knob will only rotate between 0 and 360 deg.

It worked when I rotate it slowly but when (my guess) I placed my finger close to the center plus various other point of contact combinations, and rotate, the 0 to 360 deg constraint fails.

I don't understand and can you please enlighten. Thanks.

Sub pnl_Touch  (viewtag As Object, action As Int, X As Float, Y As Float, motionevent As Object) As Boolean
    If action = 0 Then 'ACTION_DOWN
        startAngle = ATan2(X - radius, Y - radius)
    Else If action = 2 Then 'ACTION_MOVE
        Dim angle As Float = ATan2(X - radius, Y - radius)
        currentAngle = currentAngle - angle + startAngle
        Dim delta As Int = (startAngle - angle) * 180 / cPI
        If delta > 180 Then
            delta = delta - 360
        Else If delta < -180 Then
            delta = delta + 360
        End If
       
        If (currentAngle * 180 / cPI < 0.0) Then
            currentAngle = 0.0
        Else If (currentAngle * 180 / cPI > 360.0) Then
            currentAngle = (360/180) * cPI
        End If
       
        CallSubDelayed2(CallBack, EventName & "_AngleChanged", delta)
        startAngle = angle
        cvs.DrawBitmapRotated(bmp, Null, destRect, currentAngle * 180 / cPI)
        pnl.Invalidate
    End If
    Return True
End Sub

 

[Erel]

If you are only interested in the current value then you can use this code:

Sub pnl_Touch  (viewtag As Object, action As Int, X As Float, Y As Float, motionevent As Object) As Boolean
   If action = 0 Then 'ACTION_DOWN
     startAngle = ATan2(X - radius, Y - radius)
   Else If action = 2 Then 'ACTION_MOVE
     Dim angle As Float = ATan2(X - radius, Y - radius)
     currentAngle = currentAngle - angle + startAngle
     currentAngle = (currentAngle + 2 * cPI) mod (2 * cPI)
     CallSubDelayed2(CallBack, EventName & "_AngleChanged", currentAngle * 180 / cPI)
     startAngle = angle
     cvs.DrawBitmapRotated(bmp, Null, destRect, currentAngle * 180 / cPI)
     pnl.Invalidate
   End If
   Return True
End Sub

The event handler:

Sub Knob1_AngleChanged (CurrentAngleDegrees As Double)
   Log(CurrentAngleDegrees)
End Sub

 

[DT1111]

Hi Erel

That is a neat solution. Actually my attempt is to put a "hard" stop at zero deg (rotating anti-CW) and another one at 360 deg (rotating CW).

At the moment my code above works intermittently. Don't know why.

 

[Informatix]

Hi Erel

That is a neat solution. Actually my attempt is to put a "hard" stop at zero deg (rotating anti-CW) and another one at 360 deg (rotating CW).

At the moment my code above works intermittently. Don't know why.

Look at post #5

 

[DT1111]

Hi Informatix, thanks for the link. It is exactly what I have in mind ie the rotary knob. VERY impressive. Not quite rocket science but close IMHO.

It is not done via Designer and my preference is to use Designer as I have other things built around the knob. I am still interested how the same idea could be done using the above code though. Thanks again.

 

[Informatix]

It is not done via Designer and my preference is to use Designer as I have other things built around the knob. I am still interested how the same idea could be done using the above code though. Thanks again.

Then replace the Erel's code by mine in the above class...