How to split the screen with two equal LinearLayouts?

In order to split the ui into two equal parts you can use weightSum of 2 in the parent LinearLayout and assign layout_weight of 1 to each as shown below

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal"
    android:weightSum="2">

        <LinearLayout
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:orientation="vertical">

        </LinearLayout>

       <LinearLayout
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:orientation="vertical">

       </LinearLayout>


</LinearLayout>

I am answering this question after 4-5 years but best practices to do this as below

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
   xmlns:tools="http://schemas.android.com/tools"
   android:layout_width="match_parent"
   android:layout_height="match_parent"
   tools:context=".MainActivity">

   <LinearLayout
      android:id="@+id/firstLayout"
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      android:layout_toLeftOf="@+id/secondView"
      android:orientation="vertical"></LinearLayout>

   <View
      android:id="@+id/secondView"
      android:layout_width="0dp"
      android:layout_height="match_parent"
      android:layout_centerHorizontal="true" />

   <LinearLayout
      android:id="@+id/thirdLayout"
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      android:layout_toRightOf="@+id/secondView"
      android:orientation="vertical"></LinearLayout>
</RelativeLayout>

This is right approach as use of layout_weight is always heavy for UI operations. Splitting Layout equally using LinearLayout is not good practice

Just putting it out there:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#FF0000"
    android:weightSum="4"
    android:padding="5dp"> <!-- to show what the parent is -->
    <LinearLayout
        android:background="#0000FF"
        android:layout_height="0dp"
        android:layout_width="match_parent"
        android:layout_weight="2" />
    <LinearLayout
        android:background="#00FF00"
        android:layout_height="0dp"
        android:layout_width="match_parent"
        android:layout_weight="1" />
</LinearLayout>

Use the layout_weight attribute. The layout will roughly look like this:

<LinearLayout android:orientation="horizontal"
    android:layout_height="fill_parent" 
    android:layout_width="fill_parent">

    <LinearLayout 
        android:layout_weight="1" 
        android:layout_height="fill_parent" 
        android:layout_width="0dp"/>

    <LinearLayout 
        android:layout_weight="1" 
        android:layout_height="fill_parent" 
        android:layout_width="0dp"/>

</LinearLayout>