Scrollbars

[markusressel]

Hey, awesome library :)

I want to use this to build a Text Editor and want to add scrollbars for both x and y axis.
Is there some kind of listener/callback API that I missed to intercept changes in the current positioning of the ZoomLayout? If so I would be able to implement scrollbars myself and update them even when "flinging" the position.

It would also be cool to have something like this (scrollbars) built in - although it might be out of scope for this library.

Thx for the great work.

[natario1]

Thanks!

You should override onUpdate(). And get X and Y from the matrix (or ask the engine). Take a look at the ZoomLayout source code, it's pretty simple.

I think it would be in scope for both ZoomLayout and ZoomImageView so if you work this out feel free to submit a PR. Note, here we would want to let Android draw them using the view callbacks, not draw 'custom' scrollbars onDraw

[markusressel]

I'm not sure I can follow you on "let Android draw them using the view callbacks". As far as I can tell neither FrameLayout nor ImageView have built in support for scrollbars? So the only way to show scrollbars would be to add them by hand and update their position using the onUpdate() method.

Do you simply mean to use "Views" (added to the FrameLayout) which android draws instead of manually drawing rectangles in onDraw?

[natario1]

It's been a long time but as far as I remember, View or ViewGroup have builtin support for drawing scrollbars.

But the view must implement a few methods, like computeVerticalScrollRange or something like that, and then the base class will draw scrollbars based on the android:scrollbars attribute.

So if I remember correctly, you should just implement this 2? 4? methods by using the engine values. A good starting point might be the NestedScrollView source code from Google.

[natario1]

Oh and you should call awakenScrollBars when change is detected. Basically on all updates.

[markusressel]

Thx for the help, now I understand 😊

I will look into implementing this somewhere around (hopefully) this or next week.