Add recent apps in app & notification

- Introduce a RecentAppsPreferenceControler, which queries
  UsageStatsManager and displays a list of recently used apps.

- Add a control flag for this feature, intially set to false.

- Make ManageApplications a static pref item instead of dynamic one.
  This makes the RecentAppController easier to control "See all"
  preference, which is backed by ManageApplications.

- Also adjust app_items.xml layout to make app item UI consistent with
  preference item.

Change-Id: I0b9e1784faed32b3055ebf96ef98b6a5e422de50
Fix: 33265548
Test: robotests

AndroidManifest.xml

@@ -958,11 +958,6 @@
                 <category android:name="android.intent.category.VOICE_LAUNCH" />
                 <category android:name="com.android.settings.SHORTCUT" />
             </intent-filter>
-            <intent-filter android:priority="200">
-                <action android:name="com.android.settings.action.SETTINGS" />
-            </intent-filter>
-            <meta-data android:name="com.android.settings.category"
-                android:value="com.android.settings.category.ia.apps" />
             <meta-data android:name="com.android.settings.FRAGMENT_CLASS"
                 android:value="com.android.settings.applications.ManageApplications" />
             <meta-data android:name="com.android.settings.PRIMARY_PROFILE_CONTROLLED"

res/drawable/ic_chevron_right_24dp.xml

@@ -0,0 +1,27 @@
+<!--
+  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.
+  -->
+
+<vector
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    android:autoMirrored="true"
+    android:height="24dp"
+    android:width="24dp"
+    android:viewportHeight="24.0"
+    android:viewportWidth="24.0"
+    android:tint="?android:attr/colorControlNormal">
+    <path android:fillColor="#FF000000"
+          android:pathData="M10,6L8.59,7.41 13.17,12l-4.58,4.59L10,18l6,-6z" />
+</vector>

res/layout/app_item.xml

@@ -18,16 +18,16 @@
     android:layout_width="match_parent"
     android:layout_height="wrap_content"
     android:minHeight="72dp"
-    android:paddingTop="16dp"
+    android:paddingTop="12dp"
-    android:paddingBottom="16dp"
+    android:paddingBottom="12dp"
     android:gravity="top"
     android:columnCount="3"
     android:duplicateParentState="true">
 
     <ImageView
         android:id="@android:id/icon"
-        android:layout_width="40dp"
+        android:layout_width="48dp"
-        android:layout_height="40dp"
+        android:layout_height="48dp"
         android:layout_gravity="center"
         android:scaleType="fitXY"
         android:layout_marginEnd="16dip"

res/values/config.xml

@@ -105,4 +105,7 @@
     <!-- Whether or not we should tint the icon color on setting pages. -->
     <bool name="config_tintSettingIcon">true</bool>
 
+    <!-- Whether or not App & Notification screen should display recently used apps -->
+    <bool name="config_display_recent_apps">false</bool>
+
 </resources>

res/values/strings.xml

@@ -3470,6 +3470,10 @@
     <string name="install_applications">Unknown sources</string>
     <!-- Applications settings screen, setting check box title. If checked, the system allows installation of applications that are downloaded from random places, such as web sites.  [CHAR LIMIT=30] -->
     <string name="install_applications_title">Allow all app sources</string>
+    <!-- Category title listing recently used apps [CHAR_LIMIT=50]-->
+    <string name="recent_app_category_title">Recently used apps</string>
+    <!-- Preference title for showing all apps on device [CHAR_LIMIT=50]-->
+    <string name="see_all_apps_title">See all apps</string>
 
     <!-- Warning that appears below the unknown sources switch in settings -->
     <string name="install_all_warning" product="tablet">

res/xml/app_and_notification.xml

@@ -20,6 +20,27 @@
     xmlns:settings="http://schemas.android.com/apk/res/com.android.settings"
     android:title="@string/app_and_notification_dashboard_title">
 
+    <PreferenceCategory
+        android:key="recent_apps_category"
+        android:title="@string/recent_app_category_title"
+        android:order="-200">
+        <!-- Placeholder for a list of recent apps -->
+
+        <!-- See all apps button -->
+        <Preference
+            android:title="@string/applications_settings"
+            android:key="all_app_info"
+            android:summary="@string/summary_placeholder"
+            android:order="20">
+            <intent
+                android:action="android.intent.action.MAIN"
+                android:targetPackage="com.android.settings"
+                android:targetClass="com.android.settings.Settings$ManageApplicationsActivity">
+                <extra android:name="show_drawer_menu" android:value="true" />
+            </intent>
+        </Preference>
+    </PreferenceCategory>
+
     <Preference
         android:key="manage_perms"
         android:title="@string/app_permissions"

src/com/android/settings/applications/AppAndNotificationDashboardFragment.java

@@ -16,6 +16,9 @@
 
 package com.android.settings.applications;
 
+import android.app.Activity;
+import android.app.Application;
+import android.app.Fragment;
 import android.content.Context;
 import android.provider.SearchIndexableResource;
 
@@ -56,13 +59,22 @@ public class AppAndNotificationDashboardFragment extends DashboardFragment {
 
     @Override
     protected List<PreferenceController> getPreferenceControllers(Context context) {
-        return buildPreferenceControllers(context);
+        final Activity activity = getActivity();
+        final Application app;
+        if (activity != null) {
+            app = activity.getApplication();
+        } else {
+            app = null;
+        }
+        return buildPreferenceControllers(context, app, this);
     }
 
-    private static List<PreferenceController> buildPreferenceControllers(Context context) {
+    private static List<PreferenceController> buildPreferenceControllers(Context context,
+            Application app, Fragment host) {
         final List<PreferenceController> controllers = new ArrayList<>();
         controllers.add(new SpecialAppAccessPreferenceController(context));
         controllers.add(new AppPermissionsPreferenceController(context));
+        controllers.add(new RecentAppsPreferenceController(context, app, host));
         return controllers;
     }
 
@@ -78,7 +90,7 @@ public class AppAndNotificationDashboardFragment extends DashboardFragment {
 
                 @Override
                 public List<PreferenceController> getPreferenceControllers(Context context) {
-                    return buildPreferenceControllers(context);
+                    return buildPreferenceControllers(context, null, null /* host */);
                 }
             };
 }

src/com/android/settings/applications/AppCounter.java

@@ -14,7 +14,6 @@
 
 package com.android.settings.applications;
 
-import android.app.AppGlobals;
 import android.content.Context;
 import android.content.pm.ApplicationInfo;
 import android.content.pm.PackageManager;
@@ -32,7 +31,7 @@ public abstract class AppCounter extends AsyncTask<Void, Void, Integer> {
 
     public AppCounter(Context context, PackageManagerWrapper packageManager) {
         mPm = packageManager;
-        mUm = UserManager.get(context);
+        mUm = (UserManager) context.getSystemService(Context.USER_SERVICE);
     }
 
     @Override

src/com/android/settings/applications/RecentAppsPreferenceController.java

@@ -0,0 +1,312 @@
+/*
+ * 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.applications;
+
+import android.app.Application;
+import android.app.Fragment;
+import android.app.usage.UsageStats;
+import android.app.usage.UsageStatsManager;
+import android.content.Context;
+import android.content.Intent;
+import android.content.pm.PackageManager;
+import android.os.UserHandle;
+import android.support.annotation.VisibleForTesting;
+import android.support.v7.preference.Preference;
+import android.support.v7.preference.PreferenceCategory;
+import android.support.v7.preference.PreferenceScreen;
+import android.text.TextUtils;
+import android.text.format.DateUtils;
+import android.util.ArrayMap;
+import android.util.ArraySet;
+import android.util.IconDrawableFactory;
+import android.util.Log;
+
+import com.android.settings.R;
+import com.android.settings.core.PreferenceController;
+import com.android.settingslib.applications.ApplicationsState;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Calendar;
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+
+import static com.android.internal.logging.nano.MetricsProto.MetricsEvent
+        .SETTINGS_APP_NOTIF_CATEGORY;
+
+/**
+ * This controller displays a list of recently used apps and a "See all" button. If there is
+ * no recently used app, "See all" will be displayed as "App info".
+ */
+public class RecentAppsPreferenceController extends PreferenceController
+        implements Comparator<UsageStats> {
+
+    private static final String TAG = "RecentAppsCtrl";
+    private static final String KEY_PREF_CATEGORY = "recent_apps_category";
+    @VisibleForTesting
+    static final String KEY_SEE_ALL = "all_app_info";
+    private static final int SHOW_RECENT_APP_COUNT = 5;
+    private static final Set<String> SKIP_SYSTEM_PACKAGES = new ArraySet<>();
+
+    private final Fragment mHost;
+    private final PackageManager mPm;
+    private final UsageStatsManager mUsageStatsManager;
+    private final ApplicationsState mApplicationsState;
+    private final int mUserId;
+    private final IconDrawableFactory mIconDrawableFactory;
+
+    private Calendar mCal;
+    private List<UsageStats> mStats;
+
+    private PreferenceCategory mCategory;
+    private Preference mSeeAllPref;
+
+    static {
+        SKIP_SYSTEM_PACKAGES.addAll(Arrays.asList(
+                "android",
+                "com.android.phone",
+                "com.android.settings",
+                "com.android.systemui",
+                "com.android.providers.calendar",
+                "com.android.providers.media"
+        ));
+    }
+
+    public RecentAppsPreferenceController(Context context, Application app, Fragment host) {
+        this(context, app == null ? null : ApplicationsState.getInstance(app), host);
+    }
+
+    @VisibleForTesting(otherwise = VisibleForTesting.NONE)
+    RecentAppsPreferenceController(Context context, ApplicationsState appState, Fragment host) {
+        super(context);
+        mIconDrawableFactory = IconDrawableFactory.newInstance(context);
+        mUserId = UserHandle.myUserId();
+        mPm = context.getPackageManager();
+        mHost = host;
+        mUsageStatsManager =
+                (UsageStatsManager) context.getSystemService(Context.USAGE_STATS_SERVICE);
+        mApplicationsState = appState;
+    }
+
+    @Override
+    public boolean isAvailable() {
+        return true;
+    }
+
+    @Override
+    public String getPreferenceKey() {
+        return KEY_PREF_CATEGORY;
+    }
+
+    @Override
+    public void updateNonIndexableKeys(List<String> keys) {
+        super.updateNonIndexableKeys(keys);
+        // Don't index category name into search. It's not actionable.
+        keys.add(KEY_PREF_CATEGORY);
+    }
+
+    @Override
+    public void displayPreference(PreferenceScreen screen) {
+        mCategory = (PreferenceCategory) screen.findPreference(getPreferenceKey());
+        mSeeAllPref = screen.findPreference(KEY_SEE_ALL);
+        super.displayPreference(screen);
+        refreshUi(mCategory.getContext());
+    }
+
+    @Override
+    public void updateState(Preference preference) {
+        super.updateState(preference);
+        // Show total number of installed apps as See all's summary.
+        new InstalledAppCounter(mContext, InstalledAppCounter.IGNORE_INSTALL_REASON,
+                new PackageManagerWrapperImpl(mContext.getPackageManager())) {
+            @Override
+            protected void onCountComplete(int num) {
+                mSeeAllPref.setSummary(mContext.getString(R.string.apps_summary, num));
+            }
+        }.execute();
+        refreshUi(mCategory.getContext());
+    }
+
+    @Override
+    public final int compare(UsageStats a, UsageStats b) {
+        // return by descending order
+        return Long.compare(b.getLastTimeUsed(), a.getLastTimeUsed());
+    }
+
+    @VisibleForTesting
+    void refreshUi(Context prefContext) {
+        reloadData();
+        if (shouldDisplayRecentApps()) {
+            displayRecentApps(prefContext);
+        } else {
+            displayOnlyAppInfo();
+        }
+    }
+
+    @VisibleForTesting
+    void reloadData() {
+        mCal = Calendar.getInstance();
+        mCal.add(Calendar.DAY_OF_YEAR, -1);
+        mStats = mUsageStatsManager.queryUsageStats(
+                UsageStatsManager.INTERVAL_BEST, mCal.getTimeInMillis(),
+                System.currentTimeMillis());
+    }
+
+    private void displayOnlyAppInfo() {
+        mCategory.setTitle(null);
+        mSeeAllPref.setTitle(R.string.applications_settings);
+        mSeeAllPref.setIcon(null);
+        int prefCount = mCategory.getPreferenceCount();
+        for (int i = prefCount - 1; i >= 0; i--) {
+            final Preference pref = mCategory.getPreference(i);
+            if (!TextUtils.equals(pref.getKey(), KEY_SEE_ALL)) {
+                mCategory.removePreference(pref);
+            }
+        }
+    }
+
+    private void displayRecentApps(Context prefContext) {
+        mCategory.setTitle(R.string.recent_app_category_title);
+        mSeeAllPref.setTitle(R.string.see_all_apps_title);
+        mSeeAllPref.setIcon(R.drawable.ic_chevron_right_24dp);
+        final List<UsageStats> recentApps = getDisplayableRecentAppList();
+
+        // Rebind prefs/avoid adding new prefs if possible. Adding/removing prefs causes jank.
+        // Build a cached preference pool
+        final Map<String, Preference> appPreferences = new ArrayMap<>();
+        int prefCount = mCategory.getPreferenceCount();
+        for (int i = 0; i < prefCount; i++) {
+            final Preference pref = mCategory.getPreference(i);
+            final String key = pref.getKey();
+            if (!TextUtils.equals(key, KEY_SEE_ALL)) {
+                appPreferences.put(key, pref);
+            }
+        }
+        final int recentAppsCount = recentApps.size();
+        for (int i = 0; i < recentAppsCount; i++) {
+            final UsageStats stat = recentApps.get(i);
+            // Bind recent apps to existing prefs if possible, or create a new pref.
+            final String pkgName = stat.getPackageName();
+            final ApplicationsState.AppEntry appEntry =
+                    mApplicationsState.getEntry(pkgName, mUserId);
+            if (appEntry == null) {
+                continue;
+            }
+
+            boolean rebindPref = true;
+            Preference pref = appPreferences.remove(pkgName);
+            if (pref == null) {
+                pref = new Preference(prefContext);
+                rebindPref = false;
+            }
+            pref.setKey(pkgName);
+            pref.setTitle(appEntry.label);
+            pref.setIcon(mIconDrawableFactory.getBadgedIcon(appEntry.info));
+            pref.setSummary(DateUtils.getRelativeTimeSpanString(stat.getLastTimeUsed(),
+                    System.currentTimeMillis(),
+                    DateUtils.MINUTE_IN_MILLIS,
+                    DateUtils.FORMAT_ABBREV_RELATIVE));
+            pref.setOrder(i);
+            pref.setOnPreferenceClickListener(preference -> {
+                AppInfoBase.startAppInfoFragment(InstalledAppDetails.class,
+                        R.string.application_info_label, pkgName, appEntry.info.uid, mHost,
+                        1001 /*RequestCode*/, SETTINGS_APP_NOTIF_CATEGORY);
+                return true;
+            });
+            if (!rebindPref) {
+                mCategory.addPreference(pref);
+            }
+        }
+        // Remove unused prefs from pref cache pool
+        for (Preference unusedPrefs : appPreferences.values()) {
+            mCategory.removePreference(unusedPrefs);
+        }
+    }
+
+    private List<UsageStats> getDisplayableRecentAppList() {
+        final List<UsageStats> recentApps = new ArrayList<>();
+        final Map<String, UsageStats> map = new ArrayMap<>();
+        final int statCount = mStats.size();
+        for (int i = 0; i < statCount; i++) {
+            final UsageStats pkgStats = mStats.get(i);
+            if (!shouldIncludePkgInRecents(pkgStats)) {
+                continue;
+            }
+            final String pkgName = pkgStats.getPackageName();
+            final UsageStats existingStats = map.get(pkgName);
+            if (existingStats == null) {
+                map.put(pkgName, pkgStats);
+            } else {
+                existingStats.add(pkgStats);
+            }
+        }
+        final List<UsageStats> packageStats = new ArrayList<>();
+        packageStats.addAll(map.values());
+        Collections.sort(packageStats, this /* comparator */);
+        int count = 0;
+        for (UsageStats stat : packageStats) {
+            final ApplicationsState.AppEntry appEntry = mApplicationsState.getEntry(
+                    stat.getPackageName(), mUserId);
+            if (appEntry == null) {
+                continue;
+            }
+            recentApps.add(stat);
+            count++;
+            if (count >= SHOW_RECENT_APP_COUNT) {
+                break;
+            }
+        }
+        return recentApps;
+    }
+
+    /**
+     * Whether or not we should show a list of recent apps, and a see all link.
+     */
+    @VisibleForTesting
+    boolean shouldDisplayRecentApps() {
+        return mContext.getResources().getBoolean(R.bool.config_display_recent_apps)
+                && mApplicationsState != null && mStats != null && !mStats.isEmpty();
+    }
+
+    /**
+     * Whether or not the app should be included in recent list.
+     */
+    private boolean shouldIncludePkgInRecents(UsageStats stat) {
+        final String pkgName = stat.getPackageName();
+        if (stat.getLastTimeUsed() < mCal.getTimeInMillis()) {
+            Log.d(TAG, "Invalid timestamp, skipping " + pkgName);
+            return false;
+        }
+
+        if (SKIP_SYSTEM_PACKAGES.contains(pkgName)) {
+            Log.d(TAG, "System package, skipping " + pkgName);
+            return false;
+        }
+        final Intent launchIntent = new Intent().addCategory(Intent.CATEGORY_LAUNCHER)
+                .setPackage(pkgName);
+
+        if (mPm.resolveActivity(launchIntent, 0) == null) {
+            // Not visible on launcher -> likely not a user visible app, skip
+            Log.d(TAG, "Not a user visible app, skipping " + pkgName);
+            return false;
+        }
+        return true;
+    }
+}

tests/robotests/src/com/android/settings/applications/RecentAppsPreferenceControllerTest.java

@@ -0,0 +1,209 @@
+/*
+ * 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.applications;
+
+import android.app.Application;
+import android.app.usage.UsageStats;
+import android.app.usage.UsageStatsManager;
+import android.content.Context;
+import android.content.Intent;
+import android.content.pm.ResolveInfo;
+import android.os.UserHandle;
+import android.os.UserManager;
+import android.support.v7.preference.Preference;
+import android.support.v7.preference.PreferenceCategory;
+import android.support.v7.preference.PreferenceScreen;
+
+import com.android.settings.R;
+import com.android.settings.SettingsRobolectricTestRunner;
+import com.android.settings.TestConfig;
+import com.android.settingslib.applications.ApplicationsState;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.Answers;
+import org.mockito.Mock;
+import org.mockito.MockitoAnnotations;
+import org.robolectric.RuntimeEnvironment;
+import org.robolectric.annotation.Config;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import static com.google.common.truth.Truth.assertThat;
+import static org.mockito.Matchers.any;
+import static org.mockito.Matchers.anyInt;
+import static org.mockito.Matchers.anyLong;
+import static org.mockito.Matchers.anyString;
+import static org.mockito.Mockito.doNothing;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.spy;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+@RunWith(SettingsRobolectricTestRunner.class)
+@Config(manifest = TestConfig.MANIFEST_PATH, sdk = TestConfig.SDK_VERSION)
+public class RecentAppsPreferenceControllerTest {
+
+    @Mock
+    private PreferenceScreen mScreen;
+    @Mock
+    private PreferenceCategory mCategory;
+    @Mock
+    private Preference mSeeAllPref;
+    @Mock(answer = Answers.RETURNS_DEEP_STUBS)
+    private Context mMockContext;
+    @Mock
+    private UsageStatsManager mUsageStatsManager;
+    @Mock
+    private UserManager mUserManager;
+    @Mock
+    private ApplicationsState mAppState;
+
+    private Context mContext;
+    private RecentAppsPreferenceController mController;
+
+    @Before
+    public void setUp() {
+        MockitoAnnotations.initMocks(this);
+        when(mMockContext.getSystemService(Context.USAGE_STATS_SERVICE))
+                .thenReturn(mUsageStatsManager);
+        when(mMockContext.getSystemService(Context.USER_SERVICE))
+                .thenReturn(mUserManager);
+
+        mContext = RuntimeEnvironment.application;
+        mController = new RecentAppsPreferenceController(mContext, mAppState, null);
+        when(mScreen.findPreference(anyString())).thenReturn(mCategory);
+
+        when(mScreen.findPreference(RecentAppsPreferenceController.KEY_SEE_ALL))
+                .thenReturn(mSeeAllPref);
+        when(mCategory.getContext()).thenReturn(mContext);
+    }
+
+    @Test
+    public void isAlwaysAvailable() {
+        assertThat(mController.isAvailable()).isTrue();
+    }
+
+    @Test
+    public void doNotIndexCategory() {
+        final List<String> nonIndexable = new ArrayList<>();
+
+        mController.updateNonIndexableKeys(nonIndexable);
+
+        assertThat(nonIndexable).containsExactly(mController.getPreferenceKey());
+    }
+
+    @Test
+    public void onDisplayAndUpdateState_shouldRefreshUi() {
+        mController = spy(
+                new RecentAppsPreferenceController(mMockContext, (Application) null, null));
+
+        doNothing().when(mController).refreshUi(mContext);
+
+        mController.displayPreference(mScreen);
+        mController.updateState(mCategory);
+
+        verify(mController, times(2)).refreshUi(mContext);
+    }
+
+    @Test
+    public void configOff_shouldNotDisplayRecentApps() {
+        mController = new RecentAppsPreferenceController(mMockContext, (Application) null, null);
+        when(mMockContext.getResources().getBoolean(R.bool.config_display_recent_apps))
+                .thenReturn(false);
+
+        assertThat(mController.shouldDisplayRecentApps()).isFalse();
+    }
+
+    @Test
+    public void configOn_shouldDisplayRecentAppsWhenHaveData() {
+        final List<UsageStats> stats = new ArrayList<>();
+        stats.add(mock(UsageStats.class));
+        when(mMockContext.getResources().getBoolean(R.bool.config_display_recent_apps))
+                .thenReturn(true);
+        when(mUsageStatsManager.queryUsageStats(anyInt(), anyLong(), anyLong()))
+                .thenReturn(stats);
+
+        mController = new RecentAppsPreferenceController(mMockContext, mAppState, null);
+
+        mController.reloadData();
+        assertThat(mController.shouldDisplayRecentApps()).isTrue();
+    }
+
+    @Test
+    public void display_shouldNotShowRecents_showAppInfoPreference() {
+        mController = new RecentAppsPreferenceController(mMockContext, mAppState, null);
+        when(mMockContext.getResources().getBoolean(R.bool.config_display_recent_apps))
+                .thenReturn(false);
+
+        mController.displayPreference(mScreen);
+
+        verify(mCategory, never()).addPreference(any(Preference.class));
+        verify(mCategory).setTitle(null);
+        verify(mSeeAllPref).setTitle(R.string.applications_settings);
+        verify(mSeeAllPref).setIcon(null);
+    }
+
+    @Test
+    public void display_showRecents() {
+        when(mMockContext.getResources().getBoolean(R.bool.config_display_recent_apps))
+                .thenReturn(true);
+        final List<UsageStats> stats = new ArrayList<>();
+        final UsageStats stat1 = new UsageStats();
+        final UsageStats stat2 = new UsageStats();
+        final UsageStats stat3 = new UsageStats();
+        stat1.mLastTimeUsed = System.currentTimeMillis();
+        stat1.mPackageName = "pkg.class";
+        stats.add(stat1);
+
+        stat2.mLastTimeUsed = System.currentTimeMillis();
+        stat2.mPackageName = "com.android.settings";
+        stats.add(stat2);
+
+        stat3.mLastTimeUsed = System.currentTimeMillis();
+        stat3.mPackageName = "pkg.class2";
+        stats.add(stat3);
+
+        // stat1, stat2 are valid apps. stat3 is invalid.
+        when(mAppState.getEntry(stat1.mPackageName, UserHandle.myUserId()))
+                .thenReturn(mock(ApplicationsState.AppEntry.class));
+        when(mAppState.getEntry(stat2.mPackageName, UserHandle.myUserId()))
+                .thenReturn(mock(ApplicationsState.AppEntry.class));
+        when(mAppState.getEntry(stat3.mPackageName, UserHandle.myUserId()))
+                .thenReturn(null);
+        when(mMockContext.getPackageManager().resolveActivity(any(Intent.class), anyInt()))
+                .thenReturn(new ResolveInfo());
+        when(mUsageStatsManager.queryUsageStats(anyInt(), anyLong(), anyLong()))
+                .thenReturn(stats);
+
+        mController = new RecentAppsPreferenceController(mMockContext, mAppState, null);
+        mController.displayPreference(mScreen);
+
+        verify(mCategory).setTitle(R.string.recent_app_category_title);
+        // Only add stat1. stat2 is skipped because of the package name, stat3 skipped because
+        // it's invalid app.
+        verify(mCategory, times(1)).addPreference(any(Preference.class));
+
+        verify(mSeeAllPref).setTitle(R.string.see_all_apps_title);
+        verify(mSeeAllPref).setIcon(R.drawable.ic_chevron_right_24dp);
+    }
+
+}