Android Layout: width half of parent

Short answer:

1. Use android:weightSum="2" in your horizontal parent layout
2. Use android:layout_weight="1" and android:layout_width="0dp" in your children layouts.

One possible way is to have a master horizontal LinearLayout that splits the width to 2, and inside it have the vertical layout

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

            <Switch
                android:id="@+id/remember_me_switch"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:hint="@string/remember" />

            <Button
                android:id="@+id/share_button"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:onClick="loginOnclick"
                android:text="@string/login_button_text" />

        </LinearLayout>
        <!-- Right side spacer -->
        <View
           android:layout_width="0dp"
           android:layout_height="1dp"
           android:layout_weight="1" />

    </LinearLayout>

The trick is to use 0dp for the size you want manage via layout_weight! Try this

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        android:weightSum="2" >

        <LinearLayout
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:orientation="vertical"
            android:layout_weight="1"
            android:weightSum="2" >

            <Switch
                android:id="@+id/remember_me_switch"
                android:layout_width="match_parent"
                android:layout_height="0dp"
                android:layout_weight="1"
                android:hint="@string/remember" />

            <Button
                android:id="@+id/share_button"
                android:layout_width="match_parent"
                android:layout_height="0dp"
                android:layout_weight="1"
                android:onClick="loginOnclick"
                android:text="@string/login_button_text" />

        </LinearLayout>

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

    </LinearLayout>