Material-components-android: [BottomSheetBehavior] State is incorrect if updated during settling animation

[kathyma]

Description:

BottomSheetBehavior#state is not updated correctly if it was updated during the BottomSheetBehavior.SETTLING state. BottomSheetCallback$onStateChanged is not called with the correct value either.

Visually, the sheet is in the proper state.

Expected behavior:

BottomSheetBehavior#state should match its visual state and BottomSheetCallback#onStateChanged should be called with the latest state change.

Source code:

Sample project: BottomSheetDemo.zip

Snippet to reproduce bug:

class BottomSheetView @JvmOverloads constructor(context: Context, attrs: AttributeSet? = null, defStyleAttr: Int = 0, defStyleRes: Int = 0) : FrameLayout(context, attrs, defStyleAttr, defStyleRes), CoordinatorLayout.AttachedBehavior {

    private val bottomSheetBehavior = BottomSheetBehavior<BottomSheetView>()

    init {
        // Initialize sheet to be hidden and set callback for when the state changes
        bottomSheetBehavior.isHideable = true
        bottomSheetBehavior.setBottomSheetCallback(object : BottomSheetBehavior.BottomSheetCallback() {
            override fun onSlide(p0: View, p1: Float) = Unit

            override fun onStateChanged(p0: View, p1: Int) {
                println("state changed $p1")
            }

        })
        updateState(BottomSheetBehavior.STATE_HIDDEN)
    }

    override fun onAttachedToWindow() {
        super.onAttachedToWindow()

        // Update state to be expanded (from hidden)
        postDelayed({
            updateState(BottomSheetBehavior.STATE_EXPANDED)
            // Update state to be hidden (from expanded during the settling animation)
            postDelayed({
                updateState(BottomSheetBehavior.STATE_HIDDEN)
                // Query the state of the sheet after animation completes
                postDelayed({
                    println("query state ${bottomSheetBehavior.state}")
                }, 1000)
            }, 300)
        }, 3000)
    }

    private fun updateState(state: Int) {
        println("update state to $state")
        bottomSheetBehavior.state = state
    }

    override fun getBehavior(): CoordinatorLayout.Behavior<BottomSheetView> = bottomSheetBehavior
}

On 1.1.0-alpha03 and newer versions (including 1.1.0-alpha09), the above outputs:

update state to 5
update state to 3
state changed 2
update state to 5
state changed 3
query state 3

On 1.0.0, the above outputs:

update state to 5
update state to 3
state changed 2
update state to 5
state changed 3
state changed 5
query state 5

The sheet's end state should be HIDDEN (5), but it returns EXPANDED (3).

Android API version: Reproducible on API 21 (Lollipop) and 29 (Q Beta)

Material Library version: 1.1.0-alpha09

Device: Nexus 5X emulator and Pixel 3

[JadenChoi]

I'm observing same behavior as well

[alexjlockwood]

I notice this behavior as well.

[dbperez]

Seeing the same bug here as well

[melaniegoetz]

Thanks for reporting this! We're actively working on a fix for this issue now

[vecter]

Thanks @melaniegoetz

[vecter]

Hi @melaniegoetz, just checking in if you have an expected timeline for this fix. Thanks.

[melaniegoetz]

Hi there! The fix was submitted and synced out in (e057829) and will be included in the next alpha release

[vecter]

Gracias @melaniegoetz, appreciate your help here!

[bwaldvogel]

I can still observe incorrect behavior with material-components version 1.2.0.
The state change seems to be ignored when changing the state to BottomSheetBehavior.STATE_EXPANDED while the bottom sheet is currently settling.

The following workaround seems to solve the issue:

  private fun expandBottomSheet() {
+   if (bottomSheetBehavior.state == BottomSheetBehavior.STATE_SETTLING) {
+       // workaround for https://github.com/material-components/material-components-android/issues/516
+       handler.removeCallbacksAndMessages(null)
+       handler.postDelayed({ expandBottomSheet() }, 10)
+   } else {
        bottomSheetBehavior.state = BottomSheetBehavior.STATE_EXPANDED
+   }
  }