AutoCompleteTextView doesn't work when I enter first character

You will need to set the completionThreshold property of your autoCompleteView to 1.

<AutoCompleteTextView 
    android:id="@+id/someID" 
    android:layout_width="200dp"
    android:layout_height="wrap_content"
    android:completionThreshold="1" />

Or for doing it dynamically through code use

mAutoCompleteTextView.setThreshold(1)

Happy Coding :)

use i java code

autoComplete.setThreshold(1);

or in xml

android:completionThreshold="1"