getContext should not be used as it is introduced in API 23

Override getContext function to return activtiy context to avoid similar
crash in the future. It works in our case as our fragments are always
added into an activtiy.

The proper fix should be using support v4 PreferenceFragment, but given
that we are going to release the testdpc soon, I prefer to have this temp
fix first.

Bug: 27491077
Change-Id: Ifebdd7217282d8c55207cd719dc1a970c374d41f

Author: tony-mak

app/src/main/java/com/afwsamples/testdpc/common/ProfileOrParentFragment.java

@@ -141,6 +141,11 @@ protected final boolean isManagedProfileInstance() {
         return mProfileOwner && !isParentProfileInstance();
     }
 
+    @Override
+    public Context getContext() {
+        return (Context) getActivity();
+    }
+
     @Override
     public void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);

app/src/main/java/com/afwsamples/testdpc/policy/PolicyManagementFragment.java

@@ -2071,4 +2071,9 @@ private void reboot() {
      abstract class ManageLockTaskListCallback {
         public abstract void onPositiveButtonClicked(String[] lockTaskArray);
     }
+
+    @Override
+    public Context getContext() {
+        return (Context) getActivity();
+    }
 }

app/src/main/java/com/afwsamples/testdpc/profilepolicy/ProfilePolicyManagementFragment.java

@@ -401,4 +401,9 @@ private void disableIncompatibleManagementOptionsByApiLevel() {
             }
         }
     }
+
+    @Override
+    public Context getContext() {
+        return (Context) getActivity();
+    }
 }