restrict edittext to single line

Use android:maxLines="1" and android:inputType="text"

You forgot the android:maxLines attribute. And refer for android:inputType With your example, below will give this result:

<EditText 
    android:id="@+id/searchbox"  
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:maxLines="1"
    android:inputType="text"
    android:scrollHorizontally="true"
    android:ellipsize="end"
    android:layout_weight="1"
    android:layout_marginTop="2dp"
    android:drawablePadding="10dp"
    android:background="@drawable/edittext"
    android:drawableLeft="@drawable/folder_full"
    android:drawableRight="@drawable/search"
    android:paddingLeft="15dp"
    android:hint="search...">
</EditText>

Using android:singleLine="true" is deprecated.

Just add your input type and set maxline to 1 and everything will work fine

android:inputType="text"
android:maxLines="1"

android:singleLine is now deprecated. From the documentation:

This constant was deprecated in API level 3.

This attribute is deprecated. Use maxLines instead to change the layout of a static text, and use the textMultiLine flag in the inputType attribute instead for editable text views (if both singleLine and inputType are supplied, the inputType flags will override the value of singleLine).

So you could just set android:inputType="textEmailSubject" or any other value that matches the content of the field.

You must add this line in your EditText in xml:

android:maxLines="1"

android:maxLines="1"
android:inputType="text"

Add the above code to have a single line in EditText tag in your layout.

android:singleLine="true" is deprecated

This constant was deprecated in API level 3.

This attribute is deprecated. Use maxLines instead to change the layout of a static text, and use the textMultiLine flag in the inputType attribute instead for editable text views (if both singleLine and inputType are supplied, the inputType flags will override the value of singleLine).