Weights for Constraint Layout in Jetpack Compose

Question

Is there any way to use weights in Jetpack Compose ConstraintLayout chains like in XML:

<android.support.constraint.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <View
        android:id="@+id/first"
        android:layout_width="0dp"
        android:layout_height="48dp"
        android:background="#caf"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toLeftOf="@+id/start"
        app:layout_constraintHorizontal_weight="6"/>

    <View
        android:id="@+id/second"
        android:layout_width="0dp"
        android:layout_height="48dp"
        android:background="#fac"
        app:layout_constraintLeft_toRightOf="@+id/first"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintHorizontal_weight="4"/>

</android.support.constraint.ConstraintLayout>

Currently, neither ConstraintLayoutScope or ConstraintScope provide weight functionality. ConstraintLayoutScope provides createHorizontalChain(vararg elements: ConstraintLayoutReference, chainStyle: ChainStyle) (or createVerticalChain respectively) but without the option to set weights to individual elements.

With guidelines, barriers and everything else integrated I feel like there's something important missing here. Is there a way to use weights in chains or emulate their behaviour? I cannot just specify a fixed width for a element since the width of the ConstraintLayout has to match the whole screen.

Note: I understand that the new Jetpack Compose ConstraintLayout does not have a performance advantage for complex, otherwise nested, layout structures like the Android View ConstraintLayout had. I’m also aware that Row and Column provide weight functionality but I have to use ConstraintLayout in my case (reason)

nglauber nglauber · Accepted Answer · 2021-01-11T01:29:49

Have you tried fillMaxWidth(faction) modifier? I did this and worked for me...

@Composable
fun ConstraintLayoutWeightDemo() {
    ConstraintLayout(modifier = Modifier.fillMaxWidth()) {
        val (refB1, refB2, refB3) = createRefs()
        Text(
            "Text 1",
            modifier = Modifier
                .constrainAs(refB1) {
                    start.linkTo(parent.start)
                    end.linkTo(refB2.start)
                }
                .fillMaxWidth(.3f) // <<<---- 30%
                .background(Color.Red)
        )
        Text(
            "Text 2",
            modifier = Modifier
                .constrainAs(refB2) {
                    start.linkTo(refB1.end)
                    end.linkTo(refB3.start)
                }
                .fillMaxWidth(.5f) // <<<---- 50%
                .background(Color.Green)
        )
        Text(
            "Text 3",
            modifier = Modifier
                .constrainAs(refB3) {
                    start.linkTo(refB2.end)
                    end.linkTo(parent.end)
                }
                .fillMaxWidth(.2f) // <<<---- 20%
                .background(Color.Blue)
        )
    }
}

Weights for Constraint Layout in Jetpack Compose

1 Answers