'Setting the alpha value for a ConstraintLayout group

I want to ask is it possible to change the alpha for a constraint group?

<android.support.constraint.Group
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    app:constraint_referenced_ids="statusTv, statusDropDownIv"
    android:id="@+id/buttonGroup"
    android:visibility="visible"
    android:alpha="0" />

Right now the visibility tag has effect if I set it to visible/gone but the alpha tag seems to not work.

android

Solution 1:^[1]

Group is only used for controlling the visibility of Referenced Ids in app:constraint_referenced_ids. According to the documentation.

The visibility of the group will be applied to the referenced widgets. It's a convenient way to easily hide/show a set of widgets without having to maintain this set programmatically.

Solution 2:^[2]

I created this extension function to help me achieve this functionality

fun Group.setAlphaForAll(alpha: Float) = referencedIds.forEach {
    rootView.findViewById<View>(it).alpha = alpha
}

And then in code I use it like this

my_group.setAlphaForAll(0.4f)

Solution 3:^[3]

We can not use Group to change the alpha value, but we can change alpha with DataBinding.

<layout>

    <data>
        <variable name="alpha" type="float" />
    </data>

    <!-- Unrelated attributes omitted for brevity. -->

    <android.support.constraint.ConstraintLayout>
        <Button android:alpha="@{alpha}"/>
        <TextView android:alpha="@{alpha}"/>
    </android.support.constraint.ConstraintLayout>
</layout>

binding.alpha = 1.0f  // 0.0 ~ 1.0

Solution 4:^[4]

Not working to me too, try to use a ViewGroup to set alpha propertie and put your views [statusTv, statusDropDownIv] as child. To me works with ScrollView, LinearLayout and others.

I know it's sucks because Constraint Layout is expected as a flat solution layout.

Solution 5:^[5]

Currently androidx.constraintlayout.widget.Group class does not provide ability to change alpha of the grouped views. Mainly it is to be used to set Visibility (show/hide) of the grouped views with a single call.

Another solution is to inherit androidx.constraintlayout.widget.Group class and override setAlpha function.

The following code is almost exactly the same as calling Group.visibility with a difference that we are setting alpha of the views instead.

import android.content.Context
import android.util.AttributeSet
import android.view.View
import androidx.constraintlayout.widget.ConstraintLayout

class MyGroup(context: Context, attrs: AttributeSet? = null) : androidx.constraintlayout.widget.Group(context, attrs)
{
    override fun setAlpha(alpha: Float)
    {
        super.setAlpha(alpha)

        val parent = this.parent ?: return
        if(parent is ConstraintLayout)
        {
            for(i in 0..this.mCount)
            {
                val id = this.mIds[i]
                val view: View = parent.getViewById(id) ?: continue
                view.alpha = alpha
            }
        }
    }
}

Then it can be used as you would expect:

myGroup.alpha = 0.5

Sources

This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.

Source: Stack Overflow

Solution	Source
Solution 1
Solution 2	Ahmad Melegy
Solution 3	galcyurio
Solution 4	Lucas B.
Solution 5	draziw

'Setting the alpha value for a ConstraintLayout group

Solution 1:[1]

Solution 2:[2]

Solution 3:[3]

Solution 4:[4]

Solution 5:[5]