Add preference group for saved devcies.

Currently it only contains bluetooth devices.

Bug: 3240835
Test: RunSettingsRoboTests
Change-Id: Ief102e7174a4c4610dbda6b728419b303ff928f9

src/com/android/settings/connecteddevice/SavedDeviceGroupController.java

@@ -0,0 +1,109 @@
+/*
+ * Copyright (C) 2017 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.connecteddevice;
+
+import android.support.annotation.VisibleForTesting;
+import android.support.v7.preference.Preference;
+import android.support.v7.preference.PreferenceGroup;
+import android.support.v7.preference.PreferenceScreen;
+
+import com.android.settings.bluetooth.BluetoothDeviceUpdater;
+import com.android.settings.bluetooth.SavedBluetoothDeviceUpdater;
+import com.android.settings.core.PreferenceControllerMixin;
+import com.android.settings.dashboard.DashboardFragment;
+import com.android.settingslib.core.AbstractPreferenceController;
+import com.android.settingslib.core.lifecycle.Lifecycle;
+import com.android.settingslib.core.lifecycle.LifecycleObserver;
+import com.android.settingslib.core.lifecycle.events.OnStart;
+import com.android.settingslib.core.lifecycle.events.OnStop;
+
+/**
+ * Controller to maintain the {@link PreferenceGroup} for all
+ * saved devices. It uses {@link DevicePreferenceCallback} to add/remove {@link Preference}
+ */
+public class SavedDeviceGroupController extends AbstractPreferenceController
+        implements PreferenceControllerMixin, LifecycleObserver, OnStart, OnStop,
+        DevicePreferenceCallback {
+
+    private static final String KEY = "saved_device_list";
+
+    @VisibleForTesting
+    PreferenceGroup mPreferenceGroup;
+    private BluetoothDeviceUpdater mBluetoothDeviceUpdater;
+
+    public SavedDeviceGroupController(DashboardFragment fragment, Lifecycle lifecycle) {
+        super(fragment.getContext());
+        init(lifecycle, new SavedBluetoothDeviceUpdater(fragment, SavedDeviceGroupController.this));
+    }
+
+    @VisibleForTesting
+    SavedDeviceGroupController(DashboardFragment fragment, Lifecycle lifecycle,
+            BluetoothDeviceUpdater bluetoothDeviceUpdater) {
+        super(fragment.getContext());
+        init(lifecycle, bluetoothDeviceUpdater);
+    }
+
+    @Override
+    public void onStart() {
+        mBluetoothDeviceUpdater.registerCallback();
+    }
+
+    @Override
+    public void onStop() {
+        mBluetoothDeviceUpdater.unregisterCallback();
+    }
+
+    @Override
+    public void displayPreference(PreferenceScreen screen) {
+        mPreferenceGroup = (PreferenceGroup) screen.findPreference(KEY);
+        mPreferenceGroup.setVisible(false);
+        mBluetoothDeviceUpdater.setPrefContext(screen.getContext());
+        mBluetoothDeviceUpdater.forceUpdate();
+    }
+
+    @Override
+    public boolean isAvailable() {
+        return true;
+    }
+
+    @Override
+    public String getPreferenceKey() {
+        return KEY;
+    }
+
+    @Override
+    public void onDeviceAdded(Preference preference) {
+        if (mPreferenceGroup.getPreferenceCount() == 0) {
+            mPreferenceGroup.setVisible(true);
+        }
+        mPreferenceGroup.addPreference(preference);
+    }
+
+    @Override
+    public void onDeviceRemoved(Preference preference) {
+        mPreferenceGroup.removePreference(preference);
+        if (mPreferenceGroup.getPreferenceCount() == 0) {
+            mPreferenceGroup.setVisible(false);
+        }
+    }
+
+    private void init(Lifecycle lifecycle, BluetoothDeviceUpdater bluetoothDeviceUpdater) {
+        if (lifecycle != null) {
+            lifecycle.addObserver(this);
+        }
+        mBluetoothDeviceUpdater = bluetoothDeviceUpdater;
+    }
+}