This question (and answer) duplicates this one: Butterknife does not create anything in .apt_generated directory
First you need to make sure you have an Android project and not an Android library project because Butterknife handles library projects using a different approach.
To do this click Project Properties
and go to the Android
section. For further details see the Android documentation:
Then check these settings in project/.factorypath:
<factorypath>
<factorypathentry kind="WKSPJAR" id="/PotlatchClient/libs/butterknife-5.1.2.jar" enabled="true" runInBatchMode="false"/>
</factorypath>
project/.settings/org.eclipse.jdt.apt.core.prefs:
eclipse.preferences.version=1
org.eclipse.jdt.apt.aptEnabled=true
org.eclipse.jdt.apt.genSrcDir=.apt_generated
org.eclipse.jdt.apt.reconcileEnabled=true
project/.settings/org.eclipse.jdt.core.prefs:
eclipse.preferences.version=1
org.eclipse.jdt.core.compiler.processAnnotations=enabled
Finally do a refresh in Eclipse and clean to do a full rebuild.
The problem with the other suggestion is changing the JDK to 1.7 means you can only target Kitkat (4.4) or higher.