What is the difference between layout_alignEnd and layout_alignRight?

Issue

My layout:

<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:padding="8dp">

    <TextView
        android:id="@+id/crime_title"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Crime Title" />

    <TextView
        android:id="@+id/crime_date"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@id/crime_title"
        android:text="Crime Date" />

    <Button
        android:id="@+id/crime_button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignRight="@id/crime_title" />

</RelativeLayout>

Output:

If i replace android:layout_alignRight="@id/crime_title" with android:layout_alignEnd="@id/crime_title", i get the following output:

The documentation says about alignEnd :Makes the end edge of this view match the end edge of the given anchor view ID, whereas about alignRight: Makes the right edge of this view match the right edge of the given anchor view ID

Question: Isn't "a right edge" the same as "an end edge" ? And what does that blue circle, that has appeared, mean ? What is the difference between these two attributes ?

Solution

When using android:layout_alignRight you get a compiler warning saying

Consider replacing android:layout_alignRight with android:layout_alignEnd="@id/crime_title" to better support right-to-left layouts

If you dont use any right-to-left layouts you won't see any difference between android:layout_alignRight and android:layout_alignEnd. They behave same.

You can see the difference in preview while editing your layout file by enabling "Preview Right to Left". When using android:layout_alignRight your button will stay always on the right even in right to left layouts:

When using android:layout_alignEnd your button will be automatically positioned to ensure matching the end edge of the given anchor view ID. This is also what that blue circle means:

Answered By - memres