Fix Display settings summary when there is no wallpaper.

Change-Id: I715cef9dc42de1231491b5a7184f0f151d94af11
Fixes: 69905032
Test: robotests

src/com/android/settings/display/TopLevelDisplayPreferenceController.java

@@ -0,0 +1,44 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.settings.display;
+
+import android.content.Context;
+
+import com.android.settings.R;
+import com.android.settings.core.BasePreferenceController;
+
+public class TopLevelDisplayPreferenceController extends BasePreferenceController {
+
+    public TopLevelDisplayPreferenceController(Context context, String preferenceKey) {
+        super(context, preferenceKey);
+    }
+
+    @Override
+    public int getAvailabilityStatus() {
+        return AVAILABLE;
+    }
+
+    @Override
+    public CharSequence getSummary() {
+        if (new WallpaperPreferenceController(mContext, "dummy_key").isAvailable()) {
+            return mContext.getText(R.string.display_dashboard_summary);
+        } else {
+            return mContext.getText(R.string.display_dashboard_nowallpaper_summary);
+        }
+    }
+
+}