Add background activity toggle in Battery settings

We will show this preference only if the app is target prior to O
(targetSdk < O)

Bug: 33454801
Test: RunSettingsRoboTests
Change-Id: Ibd6a2147b8e7b49d2b7e3176296dd9b91ee4cc6f

src/com/android/settings/fuelgauge/BackgroundActivityPreferenceController.java

@@ -0,0 +1,106 @@
+/*
+ * 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.fuelgauge;
+
+import android.app.AppOpsManager;
+import android.content.Context;
+import android.content.pm.ApplicationInfo;
+import android.content.pm.PackageManager;
+import android.os.Build;
+import android.support.annotation.VisibleForTesting;
+import android.support.v14.preference.SwitchPreference;
+import android.support.v7.preference.Preference;
+import android.util.Log;
+import com.android.settings.core.PreferenceController;
+
+/**
+ * Controller to control whether an app can run in the background
+ */
+public class BackgroundActivityPreferenceController extends PreferenceController implements
+        Preference.OnPreferenceChangeListener {
+
+    private static final String TAG = "BgActivityPrefContr";
+    private static final String KEY_BACKGROUND_ACTIVITY = "background_activity";
+
+    private final PackageManager mPackageManager;
+    private final AppOpsManager mAppOpsManager;
+    private final String[] mPackages;
+    private final int mUid;
+
+    private String mTargetPackage;
+
+    public BackgroundActivityPreferenceController(Context context, int uid) {
+        super(context);
+        mPackageManager = context.getPackageManager();
+        mAppOpsManager = (AppOpsManager) context.getSystemService(Context.APP_OPS_SERVICE);
+        mUid = uid;
+        mPackages = mPackageManager.getPackagesForUid(mUid);
+    }
+
+    @Override
+    public void updateState(Preference preference) {
+        final int mode = mAppOpsManager
+                .checkOpNoThrow(AppOpsManager.OP_RUN_IN_BACKGROUND, mUid, mTargetPackage);
+
+        if (mode == AppOpsManager.MODE_ERRORED) {
+            preference.setEnabled(false);
+        } else {
+            ((SwitchPreference) preference).setChecked(mode != AppOpsManager.MODE_IGNORED);
+        }
+    }
+
+    @Override
+    public boolean isAvailable() {
+        if (mPackages == null) {
+            return false;
+        }
+        for (final String packageName : mPackages) {
+            if (isLegacyApp(packageName)) {
+                mTargetPackage = packageName;
+                return true;
+            }
+        }
+
+        return false;
+    }
+
+    @Override
+    public String getPreferenceKey() {
+        return KEY_BACKGROUND_ACTIVITY;
+    }
+
+    @Override
+    public boolean onPreferenceChange(Preference preference, Object newValue) {
+        boolean switchOn = (Boolean) newValue;
+        mAppOpsManager.setUidMode(AppOpsManager.OP_RUN_IN_BACKGROUND, mUid,
+                switchOn ? AppOpsManager.MODE_DEFAULT : AppOpsManager.MODE_IGNORED);
+
+        return true;
+    }
+
+    @VisibleForTesting
+    boolean isLegacyApp(final String packageName) {
+        try {
+            ApplicationInfo info = mPackageManager.getApplicationInfo(packageName,
+                    PackageManager.GET_META_DATA);
+
+            return info.targetSdkVersion < Build.VERSION_CODES.O;
+        } catch (PackageManager.NameNotFoundException e) {
+            Log.e(TAG, "Cannot find package: " + packageName, e);
+        }
+
+        return false;
+    }
+}