IllegalStateException: Fragment not attached to Activity

[lingling-fan]

//package name: com.casimirlab.simpleDeadlines
//version: 3.2.1
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.casimirlab.simpleDeadlines/com.casimirlab.simpleDeadlines.ui.MainActivity}: java.lang.IllegalStateException: Fragment DeadlineListFragment{ad2ef970} not attached to Activity
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2211)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261)
at android.app.ActivityThread.access$600(ActivityThread.java:141)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:5103)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:525)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.IllegalStateException: Fragment DeadlineListFragment{ad2ef970} not attached to Activity
at android.support.v4.app.Fragment.getLoaderManager(Fragment.java:881)
at com.casimirlab.simpleDeadlines.ui.DeadlineListFragment.setGroupFilter(DeadlineListFragment.java:178)
at com.casimirlab.simpleDeadlines.ui.MainActivity$2.onPageSelected(MainActivity.java:85)
at android.support.v4.view.ViewPager.setCurrentItemInternal(ViewPager.java:548)
at android.support.v4.view.ViewPager.setCurrentItemInternal(ViewPager.java:514)
at android.support.v4.view.ViewPager.onRestoreInstanceState(ViewPager.java:1287)
at android.view.View.dispatchRestoreInstanceState(View.java:12284)
at android.view.ViewGroup.dispatchRestoreInstanceState(ViewGroup.java:2620)
at android.view.ViewGroup.dispatchRestoreInstanceState(ViewGroup.java:2626)
at android.view.ViewGroup.dispatchRestoreInstanceState(ViewGroup.java:2626)
at android.view.View.restoreHierarchyState(View.java:12262)
at com.android.internal.policy.impl.PhoneWindow.restoreHierarchyState(PhoneWindow.java:1647)
at android.app.Activity.onRestoreInstanceState(Activity.java:938)
at android.app.Activity.performRestoreInstanceState(Activity.java:910)
at android.app.Instrumentation.callActivityOnRestoreInstanceState(Instrumentation.java:1138)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2189)

[lingling-fan]

package name: com.casimirlab.simpleDeadlines
version: 3.2.1
Exception: java.lang.IllegalStateException: Fragment DeadlineListFragment{ad2ef970} not attached to Activity
Category: Lifecycle
Description: When doing time-consuming operation in background thread(e.g, AsyncTask), a new Fragment has been created in the meantime, and was detached to the Activity before the background thread finished. The code in UI thread(e.g.,onPostExecute) calls upon a detached Fragment, throwing such exception.
Fix solution:
1: Cancel the background thread when pausing or stopping the Fragment
2: Use isAdded() to check whether the fragment is attached and then to getResources() from activity.

I'm looking forward to your reply.