Constraint Layout Vertical Align Center


Answer :

It's possible to set the center aligned view as an anchor for other views. In the example below "@+id/stat_2" centered horizontally in parent and it serves as an anchor for other views in this layout.



<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">

    <TextView
        android:id="@+id/stat_1"
        android:layout_width="80dp"
        android:layout_height="wrap_content"
        android:layout_marginEnd="8dp"
        android:gravity="center"
        android:maxLines="1"
        android:text="10"
        android:textColor="#777"
        android:textSize="22sp"
        app:layout_constraintTop_toTopOf="@+id/stat_2"
        app:layout_constraintEnd_toStartOf="@+id/divider_1" />

    <TextView
        android:id="@+id/stat_detail_1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Streak"
        android:textColor="#777"
        android:textSize="12sp"
        app:layout_constraintTop_toBottomOf="@+id/stat_1"
        app:layout_constraintStart_toStartOf="@+id/stat_1"
        app:layout_constraintEnd_toEndOf="@+id/stat_1" />

    <View
        android:id="@+id/divider_1"
        android:layout_width="1dp"
        android:layout_height="0dp"
        android:layout_marginEnd="16dp"
        android:background="#ccc"
        app:layout_constraintTop_toTopOf="@+id/stat_2"
        app:layout_constraintEnd_toStartOf="@+id/stat_2"
        app:layout_constraintBottom_toBottomOf="@+id/stat_detail_2" />

    <TextView
        android:id="@+id/stat_2"
        android:layout_width="80dp"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:maxLines="1"
        android:text="243"
        android:textColor="#777"
        android:textSize="22sp"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintBottom_toBottomOf="parent" />

    <TextView
        android:id="@+id/stat_detail_2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:maxLines="1"
        android:text="Calories Burned"
        android:textColor="#777"
        android:textSize="12sp"
        app:layout_constraintTop_toBottomOf="@+id/stat_2"
        app:layout_constraintStart_toStartOf="@+id/stat_2"
        app:layout_constraintEnd_toEndOf="@+id/stat_2" />

    <View
        android:id="@+id/divider_2"
        android:layout_width="1dp"
        android:layout_height="0dp"
        android:layout_marginStart="16dp"
        android:background="#ccc"
        app:layout_constraintBottom_toBottomOf="@+id/stat_detail_2"
        app:layout_constraintStart_toEndOf="@+id/stat_2"
        app:layout_constraintTop_toTopOf="@+id/stat_2" />

    <TextView
        android:id="@+id/stat_3"
        android:layout_width="80dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="8dp"
        android:gravity="center"
        android:maxLines="1"
        android:text="3200"
        android:textColor="#777"
        android:textSize="22sp"
        app:layout_constraintTop_toTopOf="@+id/stat_2"
        app:layout_constraintStart_toEndOf="@+id/divider_2" />

    <TextView
        android:id="@+id/stat_detail_3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:maxLines="1"
        android:text="Steps"
        android:textColor="#777"
        android:textSize="12sp"
        app:layout_constraintTop_toBottomOf="@+id/stat_3"
        app:layout_constraintStart_toStartOf="@+id/stat_3"
        app:layout_constraintEnd_toEndOf="@+id/stat_3" />

</android.support.constraint.ConstraintLayout>


Here's how it works on smallest smartphone (3.7 480x800 Nexus One) vs largest smartphone (5.5 1440x2560 Pixel XL)



Result view



If you have a ConstraintLayout with some size, and a child View with some smaller size, you can achieve centering by constraining the child's two edges to the same two edges of the parent. That is, you can write:



app:layout_constraintTop_toTopOf="parent"
app:layout_constraintBottom_toBottomOf="parent"


or



app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"


Because the view is smaller, these constraints are impossible. But ConstraintLayout will do the best it can, and each constraint will "pull" at the child view equally, thereby centering it.



This concept works with any target view, not just the parent.



Update



Below is XML that achieves your desired UI with no nesting of views and no Guidelines (though guidelines are not inherently evil).



<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="wrap_content"
    android:background="#eee">

    <TextView
        android:id="@+id/title1"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginBottom="12dp"
        android:gravity="center"
        android:textColor="#777"
        android:textSize="22sp"
        android:text="10"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toLeftOf="@+id/divider1"
        app:layout_constraintBottom_toBottomOf="parent"/>

    <TextView
        android:id="@+id/label1"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:textColor="#777"
        android:textSize="12sp"
        android:text="Streak"
        app:layout_constraintTop_toBottomOf="@+id/title1"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toLeftOf="@+id/divider1"/>

    <View
        android:id="@+id/divider1"
        android:layout_width="1dp"
        android:layout_height="55dp"
        android:layout_marginTop="12dp"
        android:layout_marginBottom="12dp"
        android:background="#ccc"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintLeft_toRightOf="@+id/title1"
        app:layout_constraintRight_toLeftOf="@+id/title2"
        app:layout_constraintBottom_toBottomOf="parent"/>

    <TextView
        android:id="@+id/title2"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginBottom="12dp"
        android:gravity="center"
        android:textColor="#777"
        android:textSize="22sp"
        android:text="243"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintLeft_toRightOf="@+id/divider1"
        app:layout_constraintRight_toLeftOf="@+id/divider2"
        app:layout_constraintBottom_toBottomOf="parent"/>

    <TextView
        android:id="@+id/label2"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:textColor="#777"
        android:textSize="12sp"
        android:text="Calories Burned"
        app:layout_constraintTop_toBottomOf="@+id/title2"
        app:layout_constraintLeft_toRightOf="@+id/divider1"
        app:layout_constraintRight_toLeftOf="@+id/divider2"/>

    <View
        android:id="@+id/divider2"
        android:layout_width="1dp"
        android:layout_height="55dp"
        android:layout_marginTop="12dp"
        android:layout_marginBottom="12dp"
        android:background="#ccc"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintLeft_toRightOf="@+id/title2"
        app:layout_constraintRight_toLeftOf="@+id/title3"
        app:layout_constraintBottom_toBottomOf="parent"/>

    <TextView
        android:id="@+id/title3"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginBottom="12dp"
        android:gravity="center"
        android:textColor="#777"
        android:textSize="22sp"
        android:text="3200"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintLeft_toRightOf="@+id/divider2"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintBottom_toBottomOf="parent"/>

    <TextView
        android:id="@+id/label3"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:textColor="#777"
        android:textSize="12sp"
        android:text="Steps"
        app:layout_constraintTop_toBottomOf="@+id/title3"
        app:layout_constraintLeft_toRightOf="@+id/divider2"
        app:layout_constraintRight_toRightOf="parent"/>

</android.support.constraint.ConstraintLayout>


enter image description here



May be i did not fully understand the problem, but, centering all view inside a ConstraintLayout seems very simple. This is what I used:



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


enter image description here



Last two lines did the trick!



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