android 4.2 多用户

packages/apps/Settings/res/xml/settings_headers.xml
    <!-- Manage users -->
    <header
        android:fragment="com.android.settings.users.UserSettings"
        android:icon="@drawable/ic_settings_multiuser"
        android:title="@string/user_settings_title"
        android:id="@+id/user_settings" />
 显示或隐藏由JAVA源码控制:
packages/apps/Settings/src/com/android/settings/Settings.java
 private void updateHeaderList(List<Header> target) {
        final boolean showDev = true;/*mDevelopmentPreferences.getBoolean(
                DevelopmentSettings.PREF_SHOW,
                android.os.Build.TYPE.equals("eng"));*/
        int i = 0;
        mHeaderIndexMap.clear();
        while (i < target.size()) {
            Header header = target.get(i);
            // Ids are integers, so downcasting
            int id = (int) header.id;
            if (id == R.id.operator_settings || id == R.id.manufacturer_settings) {
                Utils.updateHeaderToSpecificActivityFromMetaDataOrRemove(this, target, header);
            } else if (id == R.id.wifi_settings) {
                // Remove WiFi Settings if WiFi service is not available.
                if (!getPackageManager().hasSystemFeature(PackageManager.FEATURE_WIFI)) {
                    target.remove(i);
                }
            } else if (id == R.id.bluetooth_settings) {
                // Remove Bluetooth Settings if Bluetooth service is not available.
                //if (!getPackageManager().hasSystemFeature(PackageManager.FEATURE_BLUETOOTH)) {
                if (SystemProperties.get("ro.rk.bt_enable", "true").equals("false")) {
                    target.remove(header);
                }
            } else if (id == R.id.hdmi_settings) {
    if("true".equals(SystemProperties.get("ro.zed.noHdmi"))){
    target.remove(header);
    }
            }else if (id == R.id.data_usage_settings) {
                // Remove data usage when kernel module not enabled
                final INetworkManagementService netManager = INetworkManagementService.Stub
                        .asInterface(ServiceManager.getService(Context.NETWORKMANAGEMENT_SERVICE));
                try {
                    if (!netManager.isBandwidthControlEnabled()) {
                        target.remove(i);
                    }
                } catch (RemoteException e) {
                    // ignored
                }
            } else if (id == R.id.account_settings) {
                int headerIndex = i + 1;
                i = insertAccountsHeaders(target, headerIndex);
            }/** 重点看下这个地方 *****/
 else if (id == R.id.user_settings) {
                if (!UserHandle.MU_ENABLED
                        || !UserManager.supportsMultipleUsers()
                        || Utils.isMonkeyRunning()) {
                    target.remove(i);
                }
            } else if (id == R.id.development_settings) {
                if (!showDev) {
                    target.remove(i);
                }
            } else if(id == R.id.hdmi_settings){
                if(!hasHdmiFeature()){
                       target.remove(header);
                }
            }
            if (target.get(i) == header
                    && UserHandle.MU_ENABLED && UserHandle.myUserId() != 0
                    && !ArrayUtils.contains(SETTINGS_FOR_RESTRICTED, id)) {
                target.remove(i);
            }
            // Increment if the current one wasn't removed by the Utils code.
            if (target.get(i) == header) {
                // Hold on to the first header, when we need to reset to the top-level
                if (mFirstHeader == null &&
                        HeaderAdapter.getHeaderType(header) != HeaderAdapter.HEADER_TYPE_CATEGORY) {
                    mFirstHeader = header;
                }
                mHeaderIndexMap.put(id, i);
                i++;
            }
        }
    }

!UserHandle.MU_ENABLED:
public static final boolean MU_ENABLED = true;
!UserManager.supportsMultipleUsers()
 /**
     * Returns whether the system supports multiple users.
     * @return true if multiple users can be created, false if it is a single user device.
     * @hide
     */
    public static boolean supportsMultipleUsers() {
        return getMaxSupportedUsers() > 1;
    }
    /**
     * Returns the maximum number of users that can be created on this device. A return value
     * of 1 means that it is a single user device.
     * @hide
     * @return a value greater than or equal to 1 
     */
    public static int getMaxSupportedUsers() {
        // Don't allow multiple users on certain builds
        if (android.os.Build.ID.startsWith("JVP")) return 1;
        return SystemProperties.getInt("fw.max_users",
                Resources.getSystem().getInteger(R.integer.config_multiuserMaximumUsers));
    }

if (android.os.Build.ID.startsWith("JVP")) return 1;
return SystemProperties.getInt("fw.max_users",
                Resources.getSystem().getInteger(R.integer.config_multiuserMaximumUsers));