Question 306586 in Android Studio Question posted in
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Android Studio – What is the need and how to use SideEffect API in jetpack compose?

I am learning jetpack-compose and I want to understand the need for side-effect API in the android jetpack-compose library.

I have learned little about the launch effect and written code with and without it to handle out-of-composable scope work.
For both the cases the code works the same way.

  1. Without LauchEffect
Row {
        Text(text = "Hello World")
        Button(onClick = {
            state = !state
            Toast.makeText(context, "Button clicked", Toast.LENGTH_SHORT).show()
        }){
            Text(text = "Click me")
        }
    }
  1. With LauchEffect
Row {
        Text(text = "Hello World")
        Button(onClick = {
            state = !state
        }){
            Text(text = "Click me")
        }
        LaunchedEffect(key1 = state, block = {
            Toast.makeText(context, "Button clicked", Toast.LENGTH_SHORT).show()
        })
    }

Please help me understand the side-effect API and why we need a robust example

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2

Answers


  1. 0

    https://developer.android.com/jetpack/compose/side-effects

    A side-effect is a change to the state of the app that happens outside the scope of a composable function.

    onClick = { } <<< this lambda is not a composable (it is outside the scope of the function).

    It doesn’t get recomposed.

    So your onClick is a side-effect, both examples are the same (one is easier to read).

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  2. 0

    In your example there is not much difference. But LaunchedEffect allows us to react to events coming to our composable from outside. For example, lets say our composable have a connected: Boolean parameter to indicate connection status. Now we can have a LaunchedEffect(connected) that will react to changes in connection status. Another important feature of LaunchedEffect is that it will cancel previous coroutine before launching a new one, so we don’t have to worry about launching multiple coroutines performing the same task.

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