ConstraintLayout系列：ConstraintLayout实现左右均分布局

效果图：

关键代码：android:layout_width="0dp"，0dp在ConstraintLayout中的含义是match_constraint。

完整代码：

<?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=".MainActivity">

    <RelativeLayout
        android:id="@+id/rl_left"
        android:layout_width="0dp"
        android:layout_height="200dp"
        android:background="#00ff00"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toLeftOf="@id/rl_right"
        app:layout_constraintTop_toTopOf="parent" />

    <RelativeLayout
        android:id="@+id/rl_right"
        android:layout_width="0dp"
        android:layout_height="200dp"
        android:background="#ff0000"
        app:layout_constraintLeft_toRightOf="@id/rl_left"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        />

</androidx.constraintlayout.widget.ConstraintLayout>