MainActivity.kt
package com.cfsuman.kotlintutorials
import android.os.Bundle
import android.widget.*
import androidx.appcompat.app.AppCompatActivity
import androidx.constraintlayout.widget.ConstraintLayout
import androidx.constraintlayout.widget.ConstraintSet
import androidx.constraintlayout.widget.ConstraintSet.*
import androidx.transition.TransitionManager
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
// Get the widgets reference from XML layout
val rootLayout = findViewById<ConstraintLayout>(R.id.rootLayout)
val checkbox = findViewById<CheckBox>(R.id.checkbox)
val button = findViewById<Button>(R.id.button)
button.setOnClickListener {
val constraintSet = ConstraintSet()
constraintSet.clone(rootLayout)
// this block will put it horizontally center of parent
// set check box constraint start to start of parent
constraintSet.connect(
checkbox.id, // the ID of the widget to be constrained
START, // the side of the widget to constrain
PARENT_ID, // the id of the widget to constrain to
START // the side of widget to constrain to
)
// set check box constraint end to end of parent
constraintSet.connect(
checkbox.id, END, PARENT_ID, END
)
// this block put it vertically center
// set check box constraint top to top of parent
constraintSet.connect(checkbox.id,TOP, PARENT_ID, TOP)
// set check box constraint bottom to bottom of parent
constraintSet.connect(checkbox.id, BOTTOM, PARENT_ID, BOTTOM)
// optionally, apply the constraints smoothly
TransitionManager.beginDelayedTransition(rootLayout)
// both blocks will put the check box exact center of parent
// finally, apply the constraint set to constraint layout
constraintSet.applyTo(rootLayout)
}
}
}
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.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"
android:id="@+id/rootLayout"
android:background="#DCDCDC"
android:padding="24dp">
<Button
android:id="@+id/button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="64dp"
android:text="Put CheckBox Center In Parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<CheckBox
android:id="@+id/checkbox"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Check Me" />
</androidx.constraintlayout.widget.ConstraintLayout>
