Fix password constraint page crash in P- devices

Change-Id: Ia810fc71fcf14ff440ccf4d653b89bce9836f13d
FIX: 73987583

Author: tony-mak

app/src/main/java/com/afwsamples/testdpc/policy/keyguard/PasswordBlacklistFragment.java

@@ -41,7 +41,7 @@
 import java.util.Date;
 import java.util.List;
 
-@TargetApi(Build.VERSION_CODES.N)
+@TargetApi(28)
 public class PasswordBlacklistFragment extends BaseManageComponentFragment<Void>
         implements EditDeleteArrayAdapter.OnEditButtonClickListener<String> {
 

app/src/main/java/com/afwsamples/testdpc/policy/keyguard/PasswordConstraintsFragment.java

@@ -24,6 +24,7 @@
 import android.content.Intent;
 import android.net.Uri;
 import android.os.Bundle;
+import android.support.v4.os.BuildCompat;
 import android.support.v7.preference.EditTextPreference;
 import android.support.v7.preference.ListPreference;
 import android.support.v7.preference.Preference;
@@ -211,7 +212,9 @@ public void onResume() {
 
         // Settings that may have been changed by other users need updating.
         updateExpirationTimes();
-        refreshBlacklistPreferences();
+        if (BuildCompat.isAtLeastP()) {
+            refreshBlacklistPreferences();
+        }
     }
 
     @Override