Add locknow API in TestDPC

Bug: 27490667
Change-Id: Ic1fb0141f1e0dceca8100e0a8d6ab77b55869156

Author: Ricky Wai

app/src/main/java/com/afwsamples/testdpc/policy/PolicyManagementFragment.java

@@ -235,6 +235,7 @@ public class PolicyManagementFragment extends PreferenceFragment implements
     private static final String REQUEST_BUGREPORT_KEY = "request_bugreport";
     private static final String REQUEST_PROCESS_LOGS = "request_process_logs";
     private static final String RESET_PASSWORD_KEY = "reset_password";
+    private static final String LOCK_NOW_KEY = "lock_now";
     private static final String SET_ACCESSIBILITY_SERVICES_KEY = "set_accessibility_services";
     private static final String SET_ALWAYS_ON_VPN_KEY = "set_always_on_vpn";
     private static final String SET_AUTO_TIME_REQUIRED_KEY = "set_auto_time_required";
@@ -371,6 +372,7 @@ public void onCreate(Bundle savedInstanceState) {
         findPreference(LOCK_SCREEN_POLICY_KEY).setOnPreferenceClickListener(this);
         findPreference(PASSWORD_CONSTRAINTS_KEY).setOnPreferenceClickListener(this);
         findPreference(RESET_PASSWORD_KEY).setOnPreferenceClickListener(this);
+        findPreference(LOCK_NOW_KEY).setOnPreferenceClickListener(this);
         findPreference(SYSTEM_UPDATE_POLICY_KEY).setOnPreferenceClickListener(this);
         findPreference(SET_ALWAYS_ON_VPN_KEY).setOnPreferenceClickListener(this);
         findPreference(NETWORK_STATS_KEY).setOnPreferenceClickListener(this);
@@ -478,6 +480,9 @@ public void onPositiveButtonClicked(String[] lockTaskArray) {
             case RESET_PASSWORD_KEY:
                 showResetPasswordPrompt();
                 return false;
+            case LOCK_NOW_KEY:
+                mDevicePolicyManager.lockNow();
+                return true;
             case START_LOCK_TASK:
                 getActivity().startLockTask();
                 return true;

app/src/main/res/values/strings.xml

@@ -570,6 +570,8 @@
     <string name="password_reset_success">Password has been reset</string>
     <string name="password_reset_failed">Failed to reset password</string>
 
+    <string name="lock_now">Lock now</string>
+
     <!-- Strings for managing Settings -->
     <string name="settings_management_title">Settings management</string>
     <string name="stay_on_while_plugged_in">Keep the device on while plugged in</string>

app/src/main/res/xml/device_policy_header.xml

@@ -159,6 +159,9 @@
                 android:title="@string/reset_password"
                 android:dialogTitle="@string/reset_password"
                 android:inputType="textPassword" />
+        <Preference
+            android:key="lock_now"
+            android:title="@string/lock_now"/>
     </PreferenceCategory>
 
     <PreferenceCategory