Fix visibility and editability of importance fields

- Block field should always be visible
- Locked by OEM: cannot block or change importance
- Locked by default app: cannot block, can change importance
- Locked by system app: cannot block, can change importance
- system app but blockable: can block, can change importance

Test: robotests
Fixes: 131248127
Change-Id: Ifa718c84573dd5125aefa4f672a79dc4f267d515

src/com/android/settings/notification/BlockPreferenceController.java

@@ -54,13 +54,7 @@ public class BlockPreferenceController extends NotificationPreferenceController
         if (mAppRow == null) {
             return false;
         }
-        if (mChannel != null) {
-            return isChannelBlockable();
-        } else if (mChannelGroup != null) {
-            return isChannelGroupBlockable();
-        } else {
-            return !mAppRow.systemApp || (mAppRow.systemApp && mAppRow.banned);
-        }
+        return true;
     }
 
     public void updateState(Preference preference) {
@@ -78,6 +72,19 @@ public class BlockPreferenceController extends NotificationPreferenceController
             }
             bar.setDisabledByAdmin(mAdmin);
 
+            if (mChannel != null && !isChannelBlockable()) {
+                bar.setEnabled(false);
+            }
+
+            if (mChannelGroup != null && !isChannelGroupBlockable()) {
+                bar.setEnabled(false);
+            }
+
+            if (mChannel == null && mAppRow.systemApp
+                    && (!mAppRow.banned || mAppRow.lockedImportance)) {
+                bar.setEnabled(false);
+            }
+
             if (mChannel != null) {
                 bar.setChecked(!mAppRow.banned
                         && mChannel.getImportance() != NotificationManager.IMPORTANCE_NONE);