. I have a question related to the activity lifecycle My understanding from prior chats is that a reasonable approach in a lot of cases is to set things up in onResume() and shut things down in onPause(). For instance, onResume() is often a good place to register BroadcastReceivers and onPause() to unregister them. However, I've seen examples where things like canceling  Bluetooth discovery, unregistering BroadcastReceivers, and canceling downloads is done in onDestroy(). (For instance, the BluetoothChat example in the samples in the Android SDK cancels Bluetooth discovery and unregisters a BroadcastReceiver in onDestroy().) 

My understanding is that onDestroy(), unlike onPause(), is not always called. So I'm wondering why these examples shut things down in onDestroy(). Is it correct to do so?

Error:Execution failed for task ':app:transformResourcesWithMergeJavaResForDebug'.
> com.android.build.api.transform.TransformException: com.android.builder.packaging.DuplicateFileException: Duplicate files copied in APK META-INF/services/javax.annotation.processing.Processor
  	File1: /Applications/Android Studio.app/Contents/gradle/m2repository/com/tunnelvisionlabs/antlr4-annotations/4.5/antlr4-annotations-4.5.jar
  	File2: /Applications/Android Studio.app/Contents/gradle/m2repository/com/tunnelvisionlabs/antlr4-runtime/4.5/antlr4-runtime-4.5.jar

Information:Gradle tasks [:app:clean, :app:generateDebugSources, :app:generateDebugAndroidTestSources, :app:prepareDebugUnitTestDependencies, :app:mockableAndroidJar, :app:assembleDebug]
Warning:Dependency org.apache.httpcomponents:httpclient:4.1.1 is ignored for debug as it may be conflicting with the internal version provided by Android.
         In case of problem, please repackage it with jarjar to change the class packages
Warning:Dependency commons-logging:commons-logging:1.1.1 is ignored for debug as it may be conflicting with the internal version provided by Android.
         In case of problem, please repackage it with jarjar to change the class packages
Warning:Dependency org.apache.httpcomponents:httpclient:4.1.1 is ignored for release as it may be conflicting with the internal version provided by Android.
         In case of problem, please repackage it with jarjar to change the class packages
Warning:Dependency commons-logging:commons-logging:1.1.1 is ignored for release as it may be conflicting with the internal version provided by Android.
         In case of problem, please repackage it with jarjar to change the class packages
:app:clean
:app:preBuild UP-TO-DATE
:ap
...

apply plugin: 'realm-android'

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    testCompile 'junit:junit:4.12'
    compile 'com.android.support:appcompat-v7:23.1.1'
    compile 'com.android.support:support-v4:23.1.1'
    compile 'com.android.support:recyclerview-v7:23.1.1'
    compile 'com.android.support:design:23.1.1'
    compile 'com.squareup.retrofit2:converter-gson:2.0.0-beta4'
    compile 'com.squareup.picasso:picasso:2.5.2'
    compile 'com.android.support:cardview-v7:23.1.1'
    compile "io.realm:realm-gradle-plugin:0.88.2"
}

I have another question regarding what kind of cleanup needs to be after setting an adapter for a ListView. I've seen some code that uses a ListFragment for which an adapter is set in onViewCreated(). Then, in onDestroyView(), setListAdapter(null) is called. The adapter is a member variable of the fragment.

 Is setListAdapter(null) called to avoid memory leaks since the adapter holds a reference to the activity and is a member variable of the fragment? If the adapter were a local variable instead, would setListAdapter(null) still need to be called in onDestroyView()? Would this need to be done if the class were an activity rather than a fragment?