IssueTracker

Jetpack Compose version: androidx.compose:compose-bom:2023.03.00

Jetpack Compose component used: BottomSheetState

Kotlin version: 1.8.10

I noticed a bug inside the implementation of BottomSheetState. I tried calculating the absolute fractional progress of the BottomSheetState. The desired result would be a function that returns 1f if the BottomSheet is expanded and 0 if it is Hidden, so I could use the BottomSheet in combination with a MotionLayout.

@OptIn(ExperimentalMaterialApi::class)
val BottomSheetScaffoldState.currentFraction: Float
    get() {
        return if (bottomSheetState.currentValue == BottomSheetValue.Expanded && bottomSheetState.progress == 1f) {
            1f
        } else if (bottomSheetState.currentValue == BottomSheetValue.Collapsed && bottomSheetState.progress == 1f) {
            0f
        } else if (bottomSheetState.currentValue == BottomSheetValue.Expanded) {
            1 - bottomSheetState.progress
        } else {
            bottomSheetState.progress
        }
    }

This worked fine, except that the value quickly jumps from 0 to 1 when swiping down and from 1 to 0 when swiping up, which leads to a broken animation in the MotionLayout. So I started printing some outputs.

For generating the output I used:

println("state: ${bottomSheetState.currentValue}, progress: ${bottomSheetState.progress}")

When I swipe up:

I/System.out: state: Collapsed, progress: 0.99963176
I/System.out: state: Collapsed, progress: 0.9997223
I/System.out: state: Collapsed, progress: 0.99979806
I/System.out: state: Collapsed, progress: 0.99984795
I/System.out: state: Collapsed, progress: 0.9998856
I/System.out: state: Collapsed, progress: 0.999917
I/System.out: state: Collapsed, progress: 0.9999376
I/System.out: state: Collapsed, progress: 0.99995315
I/System.out: state: Collapsed, progress: 0.9999661
I/System.out: state: Collapsed, progress: 0.99997455
I/System.out: state: Collapsed, progress: 0.9999809
I/System.out: state: Collapsed, progress: 0.99998623
I/System.out: state: Collapsed, progress: 0.9999897
I/System.out: state: Collapsed, progress: 0.99999225
I/System.out: state: Collapsed, progress: 0.9999944
I/System.out: state: Collapsed, progress: 1.0 <-Remember this one here
I/System.out: state: Expanded, progress: 1.0 <-And this one here

When I swipe down:

I/System.out: state: Expanded, progress: 0.9997586
I/System.out: state: Expanded, progress: 0.9998182
I/System.out: state: Expanded, progress: 0.99986315
I/System.out: state: Expanded, progress: 0.99990064
I/System.out: state: Expanded, progress: 0.9999253
I/System.out: state: Expanded, progress: 0.9999439
I/System.out: state: Expanded, progress: 0.9999594
I/System.out: state: Expanded, progress: 0.99996954
I/System.out: state: Expanded, progress: 0.9999772
I/System.out: state: Expanded, progress: 0.99998343
I/System.out: state: Expanded, progress: 0.99998766
I/System.out: state: Expanded, progress: 0.9999907
I/System.out: state: Expanded, progress: 0.99999326
I/System.out: state: Expanded, progress: 1.0 <- And now this value
I/System.out: state: Collapsed, progress: 1.0 <- And this one

There seems to be no possibility to differenciate between state: Collapsed, progress: 1.0 when swiping up and state: Collapsed, progress: 1.0 while swiping down, which then leads to the broken animation.

In my opinion, the second last rows of the outputs are not correct and should already return the new state.

If this is intended behaviour of course, I would be happy for some feedback on how to get the absolute progress fraction of the Bottom Sheet

Kind regards