Hint user that fingerprint cannot unlock FBE keys

Show a hint text to user noting that pattern/PIN/password is
required when decrypting the credential based storage when file
based encryption is turned on.

The hint text is the same as that of the device unlock screen after
device reboot.

Bug: 27964055
Change-Id: I0d5a493bab69eae5ce4742bd07d4851387863cac

src/com/android/settings/ConfirmLockPassword.java

@@ -124,6 +124,18 @@ public class ConfirmLockPassword extends ConfirmDeviceCredentialBaseActivity {
                     || DevicePolicyManager.PASSWORD_QUALITY_COMPLEX == storedQuality
                     || DevicePolicyManager.PASSWORD_QUALITY_MANAGED == storedQuality;
 
+            // Strong auth is required when the user is locked.
+            // Currently a user does not get locked again until the device restarts. Show the
+            // hint text as "device has just been restarted".
+            mStrongAuthRequiredTextView = (TextView) view.findViewById(R.id.strongAuthRequiredText);
+            if (mIsAlpha) {
+                mStrongAuthRequiredTextView.setText(
+                        R.string.lockpassword_strong_auth_required_reason_restart_password);
+            } else {
+                mStrongAuthRequiredTextView.setText(
+                        R.string.lockpassword_strong_auth_required_reason_restart_pin);
+            }
+
             mImm = (InputMethodManager) getActivity().getSystemService(
                     Context.INPUT_METHOD_SERVICE);