Android11 热点Band值为3
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android11 热点Band值为3 ?
Android11 热点Band会出现Band=3 的情况,那么这个情况会造成什么影响呢?
本文进行源码的分析和研究!
文章目录
之前有分析热点开启流程,有兴趣可以看看:
https://blog.csdn.net/wenzhi20102321/article/details/128473734
一、造成Band=3的源码方法
frameworks\\opt\\net\\wifi\\service\\java\\com\\android\\server\\wifi\\WifiApConfigStore.java
private SoftApConfiguration sanitizePersistentApConfig(SoftApConfiguration config)
SoftApConfiguration.Builder convertedConfigBuilder = null;
// some countries are unable to support 5GHz only operation, always allow for 2GHz when
// config doesn't force channel
//channel 为0,并且band为2 ,会进入这里
if (config.getChannel() == 0 && (config.getBand() & SoftApConfiguration.BAND_2GHZ) == 0)
Log.w(TAG, "Supplied ap config band without 2.4G, add allowing for 2.4GHz");
if (convertedConfigBuilder == null)
convertedConfigBuilder = new SoftApConfiguration.Builder(config);
convertedConfigBuilder.setBand(config.getBand() | SoftApConfiguration.BAND_2GHZ);//10 | 01 --》11 (3)
return convertedConfigBuilder == null ? config : convertedConfigBuilder.build();
从上面的代码看,Band=2,并且channel=0 的情况,会重新设置Band值,这时候的Band值就是3!
可能在不同的源码版本里面(Android11或更新的源码),具体实现有差异,但是仔细研究都会发现band=3的逻辑。
无论是设置SoftApConfiguration 属性还是获取 SoftApConfiguration 属性都是会调用到 sanitizePersistentApConfig 方法。
所以出现band=3的情况,不要奇怪。
那么出现band=3,只会传递给底层是什么数据呢?
其实在framework 中,无论是Band=1 的2.4G 网络还是Band=2 的5G网络,
在未设置channel的情况,即channel=0时,都会在可用范围内随机生成一个channel值。
下面就是热点启动的重要过程,有修改热点配置的 updateApChannelConfig 方法。
二、更新热点配置和启动热点
frameworks\\opt\\net\\wifi\\service\\java\\com\\android\\server\\wifi\\SoftApManager.java
开启热点前的各种健全校验和开启成功都有相关日志,在 startSoftAp 方法!
/**
* Start a soft AP instance as configured.
*
* @return integer result code
*/
private int startSoftAp()
SoftApConfiguration config = mApConfig.getSoftApConfiguration();
if (config == null || config.getSsid() == null)
Log.e(TAG, "Unable to start soft AP without valid configuration");
return ERROR_GENERIC;
Log.d(TAG, "band " + config.getBand() + " iface "
+ mApInterfaceName + " country " + mCountryCode);
int result = setMacAddress();
if (result != SUCCESS)
return result;
result = setCountryCode();
if (result != SUCCESS)
return result;
// Make a copy of configuration for updating AP band and channel.
SoftApConfiguration.Builder localConfigBuilder = new SoftApConfiguration.Builder(config);
boolean acsEnabled = mCurrentSoftApCapability.areFeaturesSupported(
SoftApCapability.SOFTAP_FEATURE_ACS_OFFLOAD);
result = ApConfigUtil.updateApChannelConfig(
mWifiNative, mContext.getResources(), mCountryCode, localConfigBuilder, config,
acsEnabled);
if (result != SUCCESS)
Log.e(TAG, "Failed to update AP band and channel");
return result;
if (config.isHiddenSsid())
Log.d(TAG, "SoftAP is a hidden network");
if (!ApConfigUtil.checkSupportAllConfiguration(config, mCurrentSoftApCapability))
Log.d(TAG, "Unsupported Configuration detect! config = " + config);
return ERROR_UNSUPPORTED_CONFIGURATION;
if (!mWifiNative.startSoftAp(mApInterfaceName,
localConfigBuilder.build(), mSoftApListener))
Log.e(TAG, "Soft AP start failed");
return ERROR_GENERIC;
mWifiDiagnostics.startLogging(mApInterfaceName);
mStartTimestamp = FORMATTER.format(new Date(System.currentTimeMillis()));
Log.d(TAG, "Soft AP is started ");
return SUCCESS;
继续跟踪一下 updateApChannelConfig 的逻辑。
三、更新热点配置逻辑
frameworks\\opt\\net\\wifi\\service\\java\\com\\android\\server\\wifi\\util\\ApConfigUtil.java
public static int updateApChannelConfig(WifiNative wifiNative,
Resources resources,
String countryCode,
SoftApConfiguration.Builder configBuilder,
SoftApConfiguration config,
boolean acsEnabled)
/* Use default band and channel for device without HAL. */
if (!wifiNative.isHalStarted())
configBuilder.setChannel(DEFAULT_AP_CHANNEL, DEFAULT_AP_BAND);
return SUCCESS;
/* Country code is mandatory for 5GHz band. */
if (config.getBand() == SoftApConfiguration.BAND_5GHZ
&& countryCode == null)
Log.e(TAG, "5GHz band is not allowed without country code");
return ERROR_GENERIC;
/* Select a channel if it is not specified and ACS is not enabled */
//(1)channel=0 会给你适当的channel
if ((config.getChannel() == 0) && !acsEnabled)
int freq = chooseApChannel(config.getBand(), wifiNative, resources);
if (freq == -1)
/* We're not able to get channel from wificond. */
Log.e(TAG, "Failed to get available channel.");
return ERROR_NO_CHANNEL;
//(2)重点,这里会根据返回的fraq值,获取对应的channel和band,并重新设置
configBuilder.setChannel(
ScanResult.convertFrequencyMhzToChannel(freq), convertFrequencyToBand(freq));
return SUCCESS;
//从合适范围内随机获取一个channel值
public static int chooseApChannel(int apBand, WifiNative wifiNative, Resources resources)
if (!isBandValid(apBand))
Log.e(TAG, "Invalid band: " + apBand);
return -1;
List<Integer> allowedFreqList = null;
if ((apBand & SoftApConfiguration.BAND_6GHZ) != 0)
allowedFreqList = getAvailableChannelFreqsForBand(SoftApConfiguration.BAND_6GHZ,
wifiNative, resources);
if (allowedFreqList != null && allowedFreqList.size() > 0)
return allowedFreqList.get(sRandom.nextInt(allowedFreqList.size())).intValue();
//重点:Band=3,会先进这里,在5G热点范围选择适合的channel值
if ((apBand & SoftApConfiguration.BAND_5GHZ) != 0)
allowedFreqList = getAvailableChannelFreqsForBand(SoftApConfiguration.BAND_5GHZ,
wifiNative, resources);
if (allowedFreqList != null && allowedFreqList.size() > 0)
return allowedFreqList.get(sRandom.nextInt(allowedFreqList.size())).intValue();
//重点:Band=3,如果在上面未找到合适channel,也会在2.4G热点范围选择适合的channel值
if ((apBand & SoftApConfiguration.BAND_2GHZ) != 0)
allowedFreqList = getAvailableChannelFreqsForBand(SoftApConfiguration.BAND_2GHZ,
wifiNative, resources);
if (allowedFreqList != null && allowedFreqList.size() > 0)
return allowedFreqList.get(sRandom.nextInt(allowedFreqList.size())).intValue();
// If the default AP band is allowed, just use the default channel
if (containsBand(apBand, DEFAULT_AP_BAND))
Log.e(TAG, "Allowed channel list not specified, selecting default channel");
/* Use default channel. */
return convertChannelToFrequency(DEFAULT_AP_CHANNEL,
DEFAULT_AP_BAND);
Log.e(TAG, "No available channels");
return -1;
//结合底层支持和配置文件,生成可支持的chanel列表
public static List<Integer> getAvailableChannelFreqsForBand(
@BandType int band, WifiNative wifiNative, Resources resources)
if (!isBandValid(band) || isMultiband(band))
return null;
List<Integer> configuredList;
int scannerBand;
switch (band)
case SoftApConfiguration.BAND_2GHZ:
configuredList = convertStringToChannelList(resources.getString(
R.string.config_wifiSoftap2gChannelList));
scannerBand = WifiScanner.WIFI_BAND_24_GHZ;
break;
case SoftApConfiguration.BAND_5GHZ:
configuredList = convertStringToChannelList(resources.getString(
R.string.config_wifiSoftap5gChannelList));
scannerBand = WifiScanner.WIFI_BAND_5_GHZ;
break;
case SoftApConfiguration.BAND_6GHZ:
configuredList = convertStringToChannelList(resources.getString(
R.string.config_wifiSoftap6gChannelList));
scannerBand = WifiScanner.WIFI_BAND_6_GHZ;
break;
default:
return null;
// Get the allowed list of channel frequencies in MHz
int[] regulatoryArray = wifiNative.getChannelsForBand(scannerBand);
List<Integer> regulatoryList = new ArrayList<Integer>();
for (int freq : regulatoryArray)
regulatoryList.add(freq);
//可以打印查看底层支持的fraq数值,存在过底层不支持导致热点打不开的情况
Log.i(TAG, "getAvailableChannelFreqsForBand regulatoryList = " + regulatoryList );
if (configuredList == null || configuredList.isEmpty())
return regulatoryList;
List<Integer> filteredList = new ArrayList<Integer>();
// Otherwise, filter the configured list
for (int channel : configuredList)
int channelFreq = convertChannelToFrequency(channel, band);
if (regulatoryList.contains(channelFreq))
filteredList.add(channelFreq);
return filteredList;
从上面代码看,在 config.getChannel() == 0 的情况,
系统会根据底层支持的数据和配置文件的config里面对比数据获取当前设备支持的热点配置数据。
这里只是Android11 的代码分析参考,其他版本的代码可能有一定的变化,但是大概意思是相同的。
四、总结
(1)band=3,是在Band=2并且channel=0的情况出出现
(2)band=3 会在 ApConfigUtil.updateApChannelConfig 方法中重新设置band和channel值
(3)band=3 的情况,会先判断是否支持5G频段热点,如果支持会返回5G 对应的channel和band,否则判断2.4G热点配置。
所以 band=3 ,是未设置channel的情况,系统对5G热点多次检验的一个保护措施,并不影响热点使用。
因为我这边又遇到过偶现情况:wifi模组HAL异常的情况,强制设置band=2,导致热点打不开的问题。
设置band=1是没问题的,所以这个是底层不支持5G导致。打印wifiNative.getChannelsForBand返回数据就知道答案了。
所以设置band=3,有时候开启的热点是2.4G 的热点,这时候就是底层5G网络异常导致,具体是哪里问题估计要结合硬件分析。
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