I'm trying to create a ConstraintLayout to do the following;

1. on the left, a chessboard
2. on the right, controls
3. Chessboard should be a square, as big as the parent will allow
4. however at least 1/3 of parent should be left for the controls
5. importantly, if the squareness/size of the chessboard means MORE than 1/3 can be used for the control, then make the controls bigger.

Can this be done in XML? NB: obviously I can have two layouts, one for portrait, one for landscape. Happy to do this.

<?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"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".TestFragment">

    <!-- view_square should be;  -->
    <!-- be a square (nb: can *contain* a square eg a chessboard. The view itself can be rectangular -->
    <!-- as big as possible, eg in portrait mode width will determine height -->
    <!-- in landscape mode h will determine w -->
    <View
        android:id="@ id/view_square"
        android:layout_width="0dp"
        android:layout_height="0dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toLeftOf="@id/view_other"
        app:layout_constraintTop_toTopOf="parent" />

    <!-- this should be; -->
    <!-- width at a MINIMUM should be 1/3 of parent  -->
    <!-- width can be more than 1/3, if room is available after view_square's width is allocated -->
    <View
        android:id="@ id/view_other"
        android:layout_width="0dp"
        android:layout_height="0dp"
        app:layout_constraintLeft_toRightOf="@id/view_square"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>

CodePudding user response：

First Create a guideline to constrain the right end of your chessboard.

Then apply a dimension ratio of 1 to make your board a square and horizontal bias of 0 to keep it aligned to the left edge of parent.

<?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"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <View
        android:id="@ id/view_square"
        android:layout_width="0dp"
        android:layout_height="0dp"
        app:layout_constraintHorizontal_bias="0"
        app:layout_constraintDimensionRatio="1"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toLeftOf="@ id/guide_view_square"
        app:layout_constraintTop_toTopOf="parent" />

    <androidx.constraintlayout.widget.Guideline
        android:id="@ id/guide_view_square"
        android:layout_width="0dp"
        android:layout_height="0dp"
        android:orientation="vertical"
        app:layout_constraintGuide_percent="0.67"/>

    <View
        android:id="@ id/view_other"
        android:layout_width="0dp"
        android:layout_height="0dp"
        app:layout_constraintLeft_toRightOf="@id/view_square"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>

Now there are only two cases:

• square fits between parents left and guideline leaving 33% for controls
• squares size is determined by parents top and bottom, in that case horizontal bias of 0 forces it to stick to the left and controls take all remaining space