Missing: Gradient Radial Fill

[Widget]

The GradientDrawable is missing Radial fill, where the fill is like a starburst radiating from the center. This will give buttons etc. more of a 3D effect. Other HTML products I've used will also let you specify the location of the center of the radial (and linear fills to). Example: at 10,10 from the top of the image.

I don't know why Radial fill is missing, maybe it is an Android limitation?

Widget

See Gradient Radial Fill Example

 

[Erel]

You can do it with the help of the Reflection library:

Sub Activity_Create(FirstTime As Boolean)
    Dim GD As GradientDrawable
    GD.Initialize("TOP_BOTTOM", Array As Int(Colors.White, Colors.Black))
    activity.Background = gd
    SetRadialGradient(GD, Activity.Height/2)
End Sub

Sub SetRadialGradient(GD As GradientDrawable, radius As Float)
    Dim r As Reflector
    r.Target = GD
    r.RunMethod2("setGradientType", 1, "java.lang.int")
    r.RunMethod2("setGradientRadius", radius, "java.lang.float")
End Sub

 

[moster67]

Wow....there are so much hidden information here in the forum.
This tip should be added to the manual here:

Basic4android - Drawing (Core)

You can do it with the help of the Reflection library:

Sub Activity_Create(FirstTime As Boolean)
    Dim GD As GradientDrawable
    GD.Initialize("TOP_BOTTOM", Array As Int(Colors.White, Colors.Black))
    activity.Background = gd
    SetRadialGradient(GD, Activity.Height/2)
End Sub

Sub SetRadialGradient(GD As GradientDrawable, radius As Float)
    Dim r As Reflector
    r.Target = GD
    r.RunMethod2("setGradientType", 1, "java.lang.int")
    r.RunMethod2("setGradientRadius", radius, "java.lang.float")
End Sub

 

[NeoTechni]

Is there a way to do a circle-shaped gradient where it starts at one angle+color, and sweeps towards a second angle+color?

 

[derez]

If the exact shape is special, there is always the option of moving from one edge to the other by lines/arcs/circles in a loop, coloring each step in a color matched by the loop index (changing the R,G,B parameters).
This is how I did this https://www.b4x.com/android/forum/threads/class-special-drawables.19487/

 

[NeoTechni]

That uses more trigonometry than what can run in real time at a high framefrate.
It was the first thing I considered.

Right now I'm using a linear gradient, simply rotated to match the inner point. Then clipped using ExDraw to a slice of the circle.
It's not perfect, but close.

 

[derez]

If you can prepare the drawables in advance and just use the appropriate one in real time then there is no problem of prepration time.

 

[NeoTechni]

How would one do that?