currentBackStackEntryAsState() missing from Wear's NavHostController [212739653]

Fixed

Feature Request

Status Update

No update yet.

Description

je...@google.com

created issue #1

Dec 30, 2021 10:28PM

Component used: Navigation (Wear/Compose)

Version used: implementation "androidx.wear.compose:compose-navigation:1.0.0-alpha13"

Devices/Android versions reproduced on: N/A

Description:

A common pattern when using Compose + Compose Navigation to build a mobile app is to observe the current back stack entry (NavHostController.currentBackStackEntryAsState()) to determine what parts of the scaffold should be visible for certain screens.

You can see an example of this with the bottom navigation in this guide.

However, this method doesn't exist in Wear's Navigation version of the library. Can we add it?

I specifically want to only show the vignette in my scaffold when one of the destinations -> routes is a scrollable screen.

This is what I want to do:

Scaffold(
    timeText = {},
    vignette = {
        // Coming from rememberSwipeDismissableNavController()
        val currentRoute: String? =
            swipeDismissableNavController.currentBackStackEntryAsState()?.destination?.route
        
        // Only show vignette for screens with scrollable content.
        if (currentRoute == Screen.WatchList.route) {
            CustomVignette(
                visible = vignetteVisiblePreference,
                vignettePosition = VignettePosition.TopAndBottom
            )
        }
    },
    positionIndicator = {}
) { }

Let me know if you need any more information. I was hoping to add this code to the advanced sample. Thanks!

Comments

je...@google.com <je...@google.com> #2Dec 30, 2021 10:51PM

A couple of questions:

1. Have you saw crash in real device or only in simulators?
2. Do you use dynamic feature for language ID?

je...@google.com <je...@google.com> #3Dec 31, 2021 12:38AM

Tested on Android 12 Emulator with custom executor, but cannot repro this issue.

jn...@google.com <jn...@google.com> Dec 31, 2021 11:16AM

Assigned to st...@google.com.

st...@google.com <st...@google.com> Jan 5, 2022 03:06PM

Accepted by st...@google.com.

ap...@google.com <ap...@google.com> #4Jan 11, 2022 01:21PM

Second crash in the description is from a real device. Experienced it myself on two different Xiaomi phones, plus lots of crashes from users in the Google Play console.
Dynamic features are not used in the application.

As a wild guess, I have downgraded build tools from 31.0.0 to 30.0.3, compileSdk from 31 to 30, and moved all work with Language ID to the service in a separate process (just to be sure that crash can kill secondary process instead of main). This combination is in beta for 2 days by now and I don't see any SIGSEGV crashes.

st...@google.com <st...@google.com> Feb 2, 2022 04:42PM

Marked as fixed.

je...@google.com <je...@google.com> #5Feb 4, 2022 07:48PM

Hmm, I feel the crash might be something related to separate/secondary process.

I also changed compileSdk and targetSDK to 31 but still cannot repro this issue.

je...@google.com <je...@google.com> #6Feb 4, 2022 08:00PM

On the contrary, there was no separate process before, when crashes started.

In the new build (with the aforementioned changes) I can see SIGSEGV crash, but only one instead of dozens and it has a bit different backtrace:

signal 11 (SIGSEGV), code 1 (SEGV_MAPERR)
liblanguage_id_jni.so (offset 0x11e000)

backtrace:
  #00  pc 000000000003c7c0  /data/app/azagroup.reedy-mF7zTu2bv_ELlbFArwNgqA==/split_config.arm64_v8a.apk!lib/arm64-v8a/liblanguage_id_jni.so (offset 0x11e000)
  #00  pc 000000000003b960  /data/app/azagroup.reedy-mF7zTu2bv_ELlbFArwNgqA==/split_config.arm64_v8a.apk!lib/arm64-v8a/liblanguage_id_jni.so (offset 0x11e000)
  #00  pc 000000000003bb48  /data/app/azagroup.reedy-mF7zTu2bv_ELlbFArwNgqA==/split_config.arm64_v8a.apk!lib/arm64-v8a/liblanguage_id_jni.so (offset 0x11e000)
  #00  pc 000000000003bafc  /data/app/azagroup.reedy-mF7zTu2bv_ELlbFArwNgqA==/split_config.arm64_v8a.apk!lib/arm64-v8a/liblanguage_id_jni.so (offset 0x11e000)
  #00  pc 0000000000036c98  /data/app/azagroup.reedy-mF7zTu2bv_ELlbFArwNgqA==/split_config.arm64_v8a.apk!lib/arm64-v8a/liblanguage_id_jni.so (offset 0x11e000)
  #00  pc 0000000000032714  /data/app/azagroup.reedy-mF7zTu2bv_ELlbFArwNgqA==/split_config.arm64_v8a.apk!lib/arm64-v8a/liblanguage_id_jni.so (offset 0x11e000)
  #00  pc 0000000000031cac  /data/app/azagroup.reedy-mF7zTu2bv_ELlbFArwNgqA==/split_config.arm64_v8a.apk!lib/arm64-v8a/liblanguage_id_jni.so (offset 0x11e000)
  #00  pc 0000000000057438  /data/app/azagroup.reedy-mF7zTu2bv_ELlbFArwNgqA==/oat/arm64/base.odex (offset 0x57000)