Use collectAsStateWithLifecycle instead of collectAsState for collecting flows in a lifecycle-aware manner

[lydiasama]

Issue

In Jetpack Compose, we must convert any Observable type from the ViewModel to a State<T> so that Jetpack Compose can automatically recompose when the state changes.
And with the Kotlin Flow, we are using the collectAsState function in our Android Template to collect flows from the ViewModel in the Composable function. However, that function is for platform-agnostic code, not for Android-only and it's not in a lifecycle-aware manner.

Solution

Since the androidx.lifecycle:lifecycle library released the new collectAsStateWithLifecycle() collects values from a Flow in a lifecycle-aware manner, allowing your app to save unneeded app resources. It represents the latest emitted value via Compose State. Use this API as the recommended way to collect flows on Android apps.

To use collectAsStateWithLifecycle(), we need to add one more dependency:

dependencies {
      ...
      implementation("androidx.lifecycle:lifecycle-runtime-compose:2.6.0-alpha03")
}

Whereas if we continue using the collectAsState(), no dependency is needed. It's included in the compose-runtime lib already.

The example usage is:

val viewState by viewModel.state.collectAsStateWithLifecycle()

You can check out the example from google's repository here

Please take a look at the details here.
More refs from Medium: Consuming flows safely in Jetpack Compose

So it comes up with this RFC to change our Android Template use of collectAsStateWithLifecycle instead of collectAsState.

Who Benefits?

Android developers

What's Next?

Create a PR for updating the collectAsState to collectAsStateWithLifecycle

Extras 😄

Why we should use collectAsStateWithLifecycle instead of collectAsState to collect flow in Android? from ChatGpt:

[kaungkhantsoe]

I found this question about collectAsState and collectAsStateWithLifecycle. Can you provide an example of using collectAsStateWithLifecycle could be better? @lydiasama

[lydiasama]

@kaungkhantsoe But we cannot use the breakpoint to debug our app when it's in the background state, right? Many resources confirm that it still emits while the app is in the background. So let's use the latest collectAsStateWithLifecycle as Google suggested to avoid the edge cases we could not test ourselves. What do you think?

[kaungkhantsoe]

@lydiasama I do support collectAsStateWithLifecycle. I just want to find how we can know that it is better than collectAsState. 😬 Let's do it. 🚀

[doannimble]

@kaungkhantsoe You can try setting the delay (10 or more seconds before emitting the result). In the meantime, close/terminate the current screen (by back press, for example) 🤔

[kaungkhantsoe]

Yes, I did @doannimble. Still it didn't go to the break point. I delayed 10 seconds and even tried using CoroutineScope instead of viewModelScope. It didn't work.

[chornerman]

@kaungkhantsoe For the POC, please check out the below videos. We can see that collectAsState is still collecting the flow even after we minimized the app. However, collectAsStateWIthLifeCycle isn't. For more information, please check out this ref

Collect as state
https://user-images.githubusercontent.com/13492460/218009617-725f57b5-d602-4e97-9503-eb3cfcdfac34.mov

Collect as state with life cycle
https://user-images.githubusercontent.com/13492460/218009788-3a4400e2-0777-4699-9044-a19c12d8a384.mov

[doannimble]

Voted +1 👍

[thiennguyen0196]

Voted @lydiasama 👏

[luongvo]

Voted @lydiasama. Actually, according to your last raise in the channel, I applied it in my KMM's IC and it seems to work well https://github.com/luongvo/kmm-survey/blob/2ac554a171ad92a451e7450178770860c57d69de/android/src/main/java/vn/luongvo/kmm/survey/android/ui/screens/login/LoginScreen.kt#L56-L58 💪 .

[chornerman]

Voted 🚀

[Wadeewee]

Voted 🚀

[lydiasama]

@Tuubz @ryan-conway Shall we turn this into an issue? You can assign me to this task. 🙏🏻

[lydiasama]

@ryan-conway Since we got this discussion conclusion, I think we can close it.
Ref: https://github.com/nimblehq/compass/discussions/1034