How do I cause vertical two-finger swipe behavior to cause a horizontal slider to move left or right?

Question

I have a horizontal slider in my app, and I want to make it so that if you have the slider selected, you can do the two-fingered swipe up or down gesture from anywhere on the screen (The scroll up or down gesture) to move the slider left or right. I haven't been able to find anything through google about how to change vertical swipe behavior for Talkback and was wondering if there was in fact a way to change this.

Answer 1

I'd really suggest not doing this, it isn't how Android works so it will confuse your users, and be a big source of bugs as any behavior like this can cause touch errors on completely separate views. I just fixed a problem on something similar in my company's app.

But if you really want to do this- your root ViewGroup needs to intercept touch events if there are two fingers down and it moves far enough to qualify. Read https://developer.android.com/training/gestures/viewgroup#intercept for an explanation of how a parent view group can steal touch events from the child. This is the same way ScrollView works to scroll its contents. In fact, looking up the AOSP implementation of ScrollView would give you good example code.