how to MODIFY a constraint layout programmatically?

Question

Ive got a view like below :

 <org.rayanmehr.atlas.shared.customview.CustomTextView
    android:id="@+id/tvDownVoteCount"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginLeft="6dp"
    app:layout_constraintVertical_bias="0"
    app:layout_constraintTop_toBottomOf="@+id/anchorHelper"
    app:layout_constraintLeft_toRightOf="@+id/tvDownVoteIcon"
    app:layout_constraintBottom_toBottomOf="@+id/imgComment"
    />

how can i modify the value of app:layout_constraintVertical_bias or any other constraint property programmatically without having top set the whole set of the properties again in my activity ?

Answer 1

I just found the answer in here and you can use ConstraintSet to achieve this like below:

ConstraintSet constraintSet = new ConstraintSet();
constraintSet.clone(context, R.id.activity_constraint);

//for example lets change the vertical bias of tvDownVoteIcon
float biasedValue = 0.2f;
constraintSet.setVerticalBias(R.id.tvDownVoteIcon, biasedValue);

//or change the anchor
constraintSet.connect
(R.id.tvDownVoteIcon,ConstraintSet.RIGHT,R.id.txt,ConstraintSet.RIGHT,0);

//then apply
constraintSet.applyTo( (ConstraintLayout) findViewById(R.id.activity_constraint));

Answer 2

Disclaimer: I haven't used this specific functionality. This is just my interpretation on how I would try to do it.

I think that what you need is ConstraintSet. After obtaining it, you could modify it and apply it again. This is a relevant example from this article.

override fun onCreate(savedInstanceState: Bundle?) {
    ...
    val constraintSet1 = ConstraintSet()
    constraintSet1.clone(constraintLayout)
    val constraintSet2 = ConstraintSet()
    constraintSet2.clone(constraintLayout)
    constraintSet2.centerVertically(R.id.image, 0)

    var changed = false
    findViewById(R.id.button).setOnClickListener {
        TransitionManager.beginDelayedTransition(constraintLayout)
        val constraint = if (changed) constraintSet1 else constraintSet2
        constraint.applyTo(constraintLayout)
        changed = !changed
    }
}

Answer 3

Here is what I did (no need for ConstraintSet, we can work directly on the constraints themselves):

ConstraintLayout.LayoutParams params = (ConstraintLayout.LayoutParams) myView.getLayoutParams();
params.horizontalBias = 0.2f; // here is one modification for example. modify anything else you want :)
myView.setLayoutParams(params); // request the view to use the new modified params

it worked like a charm when I had a SeekBar and a TextView below it (aligned to it both left+right), and I wanted to update the TextView position to be under the SeekBar's cursor, so I had to update the horizontal bias params on the SeekBar's OnSeekBarChangeListener

Answer 4

If you are using Kotlin and you have androidx-core-ktx lib you can simply do:

someView.updateLayoutParams<ConstraintLayout.LayoutParams> { horizontalBias = 0.5f }