Introduce KeepActivitiesPreferenceController

- Create new KeepActivitiesPreferenceController
 - Create controller inside the DashboardFragment
 - Port logic from DevelopmentSettings into the controller

Bug: 34203528
Test: make RunSettingsRoboTests -j40
Change-Id: I9e15d285eee51164dd5c3a07c4f2069bf4d73383

src/com/android/settings/development/KeepActivitiesPreferenceController.java

@@ -0,0 +1,96 @@
+/*
+ * 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.development;
+
+import android.app.ActivityManager;
+import android.app.IActivityManager;
+import android.content.Context;
+import android.os.RemoteException;
+import android.provider.Settings;
+import android.support.annotation.VisibleForTesting;
+import android.support.v14.preference.SwitchPreference;
+import android.support.v7.preference.Preference;
+import android.support.v7.preference.PreferenceScreen;
+
+public class KeepActivitiesPreferenceController extends DeveloperOptionsPreferenceController
+        implements Preference.OnPreferenceChangeListener {
+
+    private static final String IMMEDIATELY_DESTROY_ACTIVITIES_KEY =
+            "immediately_destroy_activities";
+
+    @VisibleForTesting
+    static final int SETTING_VALUE_OFF = 0;
+
+    private IActivityManager mActivityManager;
+    private SwitchPreference mPreference;
+
+    public KeepActivitiesPreferenceController(Context context) {
+        super(context);
+    }
+
+    @Override
+    public String getPreferenceKey() {
+        return IMMEDIATELY_DESTROY_ACTIVITIES_KEY;
+    }
+
+    @Override
+    public void displayPreference(PreferenceScreen screen) {
+        super.displayPreference(screen);
+
+        mPreference = (SwitchPreference) screen.findPreference(getPreferenceKey());
+        mActivityManager = getActivityManager();
+    }
+
+    @Override
+    public boolean onPreferenceChange(Preference preference, Object newValue) {
+        final boolean isEnabled = (Boolean) newValue;
+        writeImmediatelyDestroyActivitiesOptions(isEnabled);
+        return true;
+    }
+
+    @Override
+    public void updateState(Preference preference) {
+        final int mode = Settings.Global.getInt(mContext.getContentResolver(),
+                Settings.Global.ALWAYS_FINISH_ACTIVITIES, SETTING_VALUE_OFF);
+        mPreference.setChecked(mode != SETTING_VALUE_OFF);
+    }
+
+    @Override
+    protected void onDeveloperOptionsSwitchEnabled() {
+        mPreference.setEnabled(true);
+    }
+
+    @Override
+    protected void onDeveloperOptionsSwitchDisabled() {
+        writeImmediatelyDestroyActivitiesOptions(false);
+        mPreference.setEnabled(false);
+        mPreference.setChecked(false);
+    }
+
+    private void writeImmediatelyDestroyActivitiesOptions(boolean isEnabled) {
+        try {
+            mActivityManager.setAlwaysFinish(isEnabled);
+        } catch (RemoteException ex) {
+            // intentional no-op
+        }
+    }
+
+    @VisibleForTesting
+    IActivityManager getActivityManager() {
+        return ActivityManager.getService();
+    }
+}