Add more preference controllers to network page.

- To support Mobile plan preference controller, extended
  LifecycleObserver pattern to also observe onCreate and onSaveInstance.

Bug: 31799836
Test: RunSettingsRoboTests
Change-Id: Ie98db7efa91f0a8b4c8a06a784d3351237e59fe0

src/com/android/settings/network/ProxyPreferenceController.java

@@ -0,0 +1,60 @@
+/*
+ * Copyright (C) 2016 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.network;
+
+import android.app.admin.DevicePolicyManager;
+import android.content.Context;
+import android.support.v7.preference.Preference;
+import android.support.v7.preference.PreferenceScreen;
+
+import com.android.settings.core.PreferenceController;
+
+public class ProxyPreferenceController extends PreferenceController {
+
+    private static final String KEY_PROXY_SETTINGS = "proxy_settings";
+
+    public ProxyPreferenceController(Context context) {
+        super(context);
+    }
+
+    @Override
+    public boolean handlePreferenceTreeClick(Preference preference) {
+        return false;
+    }
+
+    @Override
+    protected boolean isAvailable() {
+        // proxy UI disabled until we have better app support
+        return false;
+    }
+
+    @Override
+    public void displayPreference(PreferenceScreen screen) {
+        super.displayPreference(screen);
+        // Enable Proxy selector settings if allowed.
+        final Preference pref = screen.findPreference(KEY_PROXY_SETTINGS);
+        if (pref != null) {
+            final DevicePolicyManager dpm = (DevicePolicyManager)
+                    mContext.getSystemService(Context.DEVICE_POLICY_SERVICE);
+            pref.setEnabled(dpm.getGlobalProxyAdmin() == null);
+        }
+    }
+
+    @Override
+    protected String getPreferenceKey() {
+        return KEY_PROXY_SETTINGS;
+    }
+}