Aligning textviews on the left and right edges in Android layout

Use a RelativeLayout with layout_alignParentLeft and layout_alignParentRight:

<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/RelativeLayout01" 
    android:layout_width="fill_parent" 
    android:layout_height="fill_parent"
    android:padding="10dp">

    <TextView 
        android:layout_width="wrap_content" 
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true" 
        android:id="@+id/mytextview1"/>

    <TextView 
        android:layout_width="wrap_content" 
        android:layout_height="wrap_content" 
        android:layout_alignParentRight="true" 
        android:id="@+id/mytextview2"/>

</RelativeLayout>

Also, you should probably be using dip (or dp) rather than sp in your layout. sp reflect text settings as well as screen density so they're usually only for sizing text items.

You can use the gravity property to "float" views.

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

    <LinearLayout 
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"
            android:gravity="center_vertical|center_horizontal"
            android:orientation="horizontal">

        <TextView  
            android:layout_width="wrap_content" 
            android:layout_height="wrap_content" 
            android:gravity="left"
            android:layout_weight="1"
            android:text="Left Aligned"
            />

        <TextView  
            android:layout_width="wrap_content" 
            android:layout_height="wrap_content"
            android:gravity="right"
            android:layout_weight="1"
            android:text="Right Aligned"
            />
    </LinearLayout>

</LinearLayout>

It can be done with LinearLayout (less overhead and more control than the Relative Layout option). Give the second view the remaining space so gravity can work. Tested back to API 16.

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Aligned left" />

    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="end"
        android:text="Aligned right" />
</LinearLayout> 

If you want to limit the size of the first text view, do this:

Adjust weights as required. Relative layout won't allow you to set a percentage weight like this, only a fixed dp of one of the views

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <TextView
        android:layout_width="0dp"
        android:layout_weight="1"
        android:layout_height="wrap_content"
        android:text="Aligned left but too long and would squash the other view" />

    <TextView
        android:layout_width="0dp"
        android:layout_weight="1"
        android:layout_height="wrap_content"
        android:gravity="end"
        android:text="Aligned right" />
</LinearLayout>

Even with Rollin_s's tip, Dave Webb's answer didn't work for me. The text in the right TextView was still overlapping the text in the left TextView.

I eventually got the behavior I wanted with something like this:

<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/RelativeLayout01" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent"
    android:padding="10dp">

<TextView 
    android:id="@+id/mytextview1"
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content"
    android:layout_alignParentLeft="true" />

<TextView 
    android:id="@+id/mytextview2"
    android:layout_width="match_parent" 
    android:layout_height="wrap_content" 
    android:layout_toRightOf="@id/mytextview1"
    android:gravity="right"/>

</RelativeLayout>

Note that mytextview2 has "android:layout_width" set as "match_parent".

Hope this helps someone!