CODEWITHSUNDEEP
androidandroid-databindingandroid-constraintlayout
Rishabh876
Rishabh876

Reputation: 3190

Could not resolve the two-way binding attribute 'visibility' on type 'android.support.constraint.Group'

I have two groups defined inside a ConstraintLayout in my layout. I want them to have visibility opposite to each other. So if group1 is visible then group2 should be gone and vice versa. I am trying to use data binding to achieve this.

<data>

    <import type="android.view.View" />

</data>

<android.support.constraint.Group
                    android:id="@+id/group1"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:visibility="visible"
                    app:constraint_referenced_ids="..." />

<android.support.constraint.Group
                    android:id="@+id/group2"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:visibility="@{group1.visibility == View.VISIBLE? View.GONE : View.VISIBLE}"
                    app:constraint_referenced_ids="..." />

But I am getting a compilation error that says:

****/ data binding error ****msg:Could not resolve the two-way binding attribute 'visibility' on type 'android.support.constraint.Group'

What am I doing wrong?

Upvotes: 8

Views: 2568

Answers (3)

Agent_L
Agent_L

Reputation: 5421

It "works". Kind of:

<android.support.constraint.Group
                android:id="@+id/group1"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:visibility="@{viewmodel.shouldShow ? View.VISIBLE : View.GONE }"
                app:constraint_referenced_ids="..." />

<android.support.constraint.Group
                android:id="@+id/group2"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:visibility="@{group1.visibility == View.VISIBLE ? View.GONE : View.VISIBLE}"
                app:constraint_referenced_ids="..." />

This works because the engine doesn't actually bind one View's visibility to another View's visibility. It notices that both bindings ultimately resolve to the same, bindable source: property of the viewModel - and generates another binding to the same source. It's merely a syntactic sugar (possibly that's why it depends on details that shouldn't matter, like the order of views in XML). I think it was meant to cut down on repetition and nothing more.

Actual binding to another View's property is possible where the property has all the piping for two-way databinding. Like EditText.text or CheckBox.checked. In those cases you get actual View-to-View binding.

Upvotes: 0

George Mount
George Mount

Reputation: 20926

The problem is that android:visibility doesn't support two-way data binding. There is no event to notify when the visibility changes, so there is no way to notify when the property should update.

Upvotes: 2

Alan Todtenkopf
Alan Todtenkopf

Reputation: 472

I don't know why that error is happening, but this worked for me:

    group1.getVisibility() == View.VISIBLE

With that said, I couldn't get the constraint.Group to work as advertised. Also, to make them opposite each other, presumably you would need similar logic in group1's visibility, but that would be circular. Why not bind these to a ViewModel that controls when each should be visible?

Upvotes: 6

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