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最新推荐文章于 2025-04-16 20:42:40 发布

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分类专栏： Android 文章标签：网络 android mobile network action service

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系统中对网络的判断和选在是在Connectivityervice这个服务中来处理的，在系统启动的时候会启动这个系统服务：

系统启动完毕后，ConnectivityService在系统启动的时候就启动了。

在android内部，用framework/base/core/res/res/values/config.xml中定义了网络的类型：

<string-array translatable="false"name="networkAttributes">

<item>"default,wifi,0"</item>

<item>"default,mobile,0"</item>

<item>"mms,mobile,1"</item>

<item>"supl,mobile,1"</item>

<item>"dun,mobile,1"</item>

<item>"hipri,mobile,2"</item>

</string-array>

<string-array translatable="false"name="radioAttributes">

<item>"mobile,0,1"</item>

</string-array>

ConnectivityManager定义了向对应的字符串常量：

public static final intTYPE_MOBILE = 0;

/**

* The Default WIFI data connection. Whenactive, all data traffic

* will use this connection by default. Should not coexist with other

* default connections.

public static final intTYPE_WIFI = 1;

/**

* An MMS-specific Mobiledata connection. This connection may be the

* same as {@link #TYPEMOBILE} but itmay be different. This is used

* by applications needing to talk to thecarrier's Multimedia Messaging

* Service servers. It may coexist withdefault data connections.

* {@hide}

public static final int TYPE_MOBILE_MMS = 2;

/**

* A SUPL-specific Mobiledata connection. This connection may be the

* same as {@link #TYPEMOBILE} but itmay be different. This is used

* by applications needing to talk to thecarrier's Secure User Plane

* Location servers for help locating thedevice. It may coexist with

* default data connections.

* {@hide}

public static final int TYPE_MOBILE_SUPL = 3;

/**

* A DUN-specific Mobiledata connection. This connection may be the

* same as {@link #TYPEMOBILE} but itmay be different. This is used

* by applicaitons performing a Dial UpNetworking bridge so that

* the carrier is aware of DUN traffic. Itmay coexist with default data

* connections.

* {@hide}

public static final int TYPE_MOBILE_DUN = 4;

/**

* A High Priority Mobiledata connection. This connection is typically

* the same as {@link #TYPEMOBILE} butthe routing setup is different.

* Only requesting processes will have access tothe Mobile DNS servers

* and only IP's explicitly requested via {@link #requestRouteToHost}

* will route over this interface.

*{@hide}

public static final int TYPE_MOBILE_HIPRI = 5;

/** {@hide}*/

public static final int MAX_RADIO_TYPE =TYPE_WIFI;

/** {@hide}*/

public static final int MAX_NETWORK_TYPE =TYPE_MOBILE_HIPRI;

public static final int DEFAULT_NETWORK_PREFERENCE =TYPE_WIFI;

并设置了默认的网络连接是TYPE_WIFI.

ConnectivityManager的方法是通过AIDL的使用，调用ConnectivityService中的方法来实现的。ConnectivityService继承了IConnectivityManage.stub.

在ConnectivityService内部，定义了两个类来解析xml中的网络类型，类的代码如下：

private class NetworkAttributes {

/**

* Class for holdingsettings read from resources.

public String mName;

public int mType;

public int mRadio;

public int mPriority;

public NetworkInfo.StatemLastState;

publicNetworkAttributes(String init) {

String fragments[] = init.split(",");

mName= fragments[0].toLowerCase();

if(fragments[1].toLowerCase().equals("wifi")) {

mRadio = ConnectivityManager.TYPE_WIFI;

}else {

mRadio = ConnectivityManager.TYPE_MOBILE;

}

if(mName.equals("default")) {

mType = mRadio;

}else if (mName.equals("mms")) {

mType = ConnectivityManager.TYPE_MOBILE_MMS;

}else if (mName.equals("supl")) {

mType = ConnectivityManager.TYPE_MOBILE_SUPL;

}else if (mName.equals("dun")) {

mType = ConnectivityManager.TYPE_MOBILE_DUN;

}else if (mName.equals("hipri")) {

mType = ConnectivityManager.TYPE_MOBILE_HIPRI;

}

mPriority = Integer.parseInt(fragments[2]);

mLastState = NetworkInfo.State.UNKNOWN;

}

public boolean isDefault() {

return (mType == mRadio);

}

private class RadioAttributes {

public String mName;

public int mPriority;

public int mSimultaneity;

public int mType;

public RadioAttributes(Stringinit) {

String fragments[] = init.split(",");

mName= fragments[0].toLowerCase();

mPriority = Integer.parseInt(fragments[1]);

mSimultaneity = Integer.parseInt(fragments[2]);

if(mName.equals("wifi")) {

mType = ConnectivityManager.TYPE_WIFI;

}else {

mType = ConnectivityManager.TYPE_MOBILE;

}

并通过一下代码，来给网络分配优先级，

mPriorityList = new int[naStrings.length];

{

intpriority = 0; //lowest

intnextPos = naStrings.length-1;

while(nextPos>-1) {

for (int i = 0; i < mNetAttributes.length; i++) {

if(mNetAttributes[i].mPriority == priority) {

mPriorityList[nextPos--] = i;

}

priority++;

}

mNetRequestersPids =

new ArrayList[ConnectivityManager.MAX_NETWORK_TYPE+1];

for (int i=0;i<=ConnectivityManager.MAX_NETWORK_TYPE; i++) {

mNetRequestersPids[i]= new ArrayList();

}

其中，TYPE_MOBILE_HIPRI的优先级最高，其次为TYPE_MOBILE_MMS，TYPE_MOBILE_SUPL，TYPE_MOBILE_DUN，

优先级最低的为TYPE_WIFI，TYPE_MOBILE。TYPE_WIFI，TYPE_MOBILE两个网络类型中，TYPE_WIFI大于TYPE_MOBILE的优先级，

在打开wifi的连接后，mobile网络会被关闭。wifi网络连接关闭后，mobile网络会重新连接。在处理网络连接的Handler的代码中有处理：

private void handleConnect(NetworkInfo info) {

int type = info.getType();

Log.d(TAG, "Got NetworkConnection Succ from Driver nwtype="+type);

// snapshot isFailover,because sendConnectedBroadcast() resets it

boolean isFailover =info.isFailover();

NetworkStateTracker thisNet =mNetTrackers[type];

// if this is a default netand other default is running

// kill the one not preferred

if(mNetAttributes[type].isDefault()) {

if(mActiveDefaultNetwork != -1 && mActiveDefaultNetwork != type) {

if ((type != mNetworkPreference &&

mNetAttributes[mActiveDefaultNetwork].mPriority >

mNetAttributes[type].mPriority) ||

mNetworkPreference == mActiveDefaultNetwork) {

if(!((SystemProperties.get(CNE.UseCne,"false").equals("true")||

SystemProperties.get(CNE.UseCne,"false").equals("TRUE"))&&

CNE.isCndUp)) {

// don't accept this one

if (DBG) Log.v(TAG, "Not broadcasting CONNECT_ACTION " +

"to torn down network " + info.getTypeName());

teardown(thisNet);

}

return;

} else {

// tear down the other

NetworkStateTracker otherNet =

mNetTrackers[mActiveDefaultNetwork];

if (DBG) Log.v(TAG, "Policy requires " +

otherNet.getNetworkInfo().getTypeName() +

" teardown");

if(!((SystemProperties.get(CNE.UseCne,"false").equals("true")||

SystemProperties.get(CNE.UseCne,"false").equals("TRUE"))&&

CNE.isCndUp)) {

if (DBG) Log.i(TAG, "CNE To support Simultaneous Nws we"+

" will not tear down other nw");

if (!teardown(otherNet)) {

Log.e(TAG, "Network declined teardown request");

return;

}

if (isFailover) {

otherNet.releaseWakeLock();

}

mActiveDefaultNetwork= type;

}

thisNet.setTeardownRequested(false);

thisNet.updateNetworkSettings();

handleConnectivityChange();

sendConnectedBroadcast(info);

}

SystemServer启动ConnectivityService，ConnectivityService启动对网络的监视器。

在SystemServer的run()函数中，启动ConnectivityService的代码：

try {

Log.i(TAG, "Connectivity Service");

connectivity = ConnectivityService.getInstance(context);

ServiceManager.addService(Context.CONNECTIVITY_SERVICE, connectivity);

connectivity.startCne();

}catch (Throwable e) {

Log.e(TAG, "Failure starting Connectivity Service", e);

}

在ConnectivityService的构造函数中启动网络监视器的代码：

if (DBG) Log.v(TAG, "Starting Wifi Service.");

WifiStateTracker wst = newWifiStateTracker(context, mHandler);

WifiService wifiService = newWifiService(context, wst);

ServiceManager.addService(Context.WIFI_SERVICE,wifiService);

mNetTrackers[ConnectivityManager.TYPE_WIFI] = wst;

mNetTrackers[ConnectivityManager.TYPE_MOBILE] =

new MobileDataStateTracker(context, mHandler,

ConnectivityManager.TYPE_MOBILE, Phone.APN_TYPE_DEFAULT,

"MOBILE");

mNetTrackers[ConnectivityManager.TYPE_MOBILE_MMS] =

new MobileDataStateTracker(context, mHandler,

ConnectivityManager.TYPE_MOBILE_MMS, Phone.APN_TYPE_MMS,

"MOBILE_MMS");

mNetTrackers[ConnectivityManager.TYPE_MOBILE_SUPL] =

new MobileDataStateTracker(context, mHandler,

ConnectivityManager.TYPE_MOBILE_SUPL, Phone.APN_TYPE_SUPL,

"MOBILE_SUPL");

mNetTrackers[ConnectivityManager.TYPE_MOBILE_DUN] =

new MobileDataStateTracker(context, mHandler,

ConnectivityManager.TYPE_MOBILE_DUN, Phone.APN_TYPE_DUN,

"MOBILE_DUN");

mNetTrackers[ConnectivityManager.TYPE_MOBILE_HIPRI] =

new MobileDataStateTracker(context, mHandler,

ConnectivityManager.TYPE_MOBILE_HIPRI, Phone.APN_TYPE_HIPRI,

"MOBILE_HIPRI");

mNumDnsEntries = 0;

mTestMode =SystemProperties.get("cm.test.mode").equals("true")

&&SystemProperties.get("ro.build.type").equals("eng");

for (NetworkStateTracker t :mNetTrackers)

t.startMonitoring();

// Constructing this startsit too

mWifiWatchdogService = newWifiWatchdogService(context, wst);

在settings中可以设置网络连接，比如打开wifi，打开bluetooth,设置apn的连接等等，在设置完成后，设置的消息会存在一个数据库中保存，并发送系统消息来广播网络设置的变化。

在网络监视器中捕捉了settings中发出的相应的网络广播信息，

网络监视器中注册了settings中网络变化的信息，有变化会做相应的处理，并将处理的结果存储在NetworkInfo类的一个对象中，在ConnectivityService中通过

public NetworkInfogetNetworkInfo(int networkType)方法可以得知当前networkType类型网络的连接情况。

在app中，我们可以通过ConnectivityManager来获取当前的网络信息，并能指定当前程序需要的网络类型：

ConnectivityManager mCnn =context.getSystemService(context.NONNECTIVITY_SERVICE);

NetworkInfo mNetinfo =mCnn.getActiveNetworkInfo();

mCnn.setNetworkPreference(int preference);//设定首选网络类型。

假如没有设定，网络类型为系统默认。在wifi，3G网络同时存在的情况下，系统会默认的调用wifi网络，加载wifi的驱动，走wifi网络。

wifi子系统的分析：

初始化

在 SystemServer 启动的时候,会生成一个 ConnectivityService 的实例,

try {

Log.i(TAG, "Starting Connectivity Service.");

ServiceManager.addService(Context.CONNECTIVITY_SERVICE, new

ConnectivityService(context));

} catch (Throwable e) {

Log.e(TAG, "Failure starting Connectivity Service", e);

}

ConnectivityService 的构造函数会创建 WifiService,

if (DBG)Log.v(TAG, "Starting Wifi Service.");

mWifiStateTracker= new WifiStateTracker(context, handler);

WifiServicewifiService = new WifiService(context, mWifiStateTracker);

ServiceManager.addService(Context.WIFI_SERVICE, wifiService);

WifiStateTracker 会创建 WifiMonitor 接收来自底层的事件,WifiService 和 WifiMonitor 是整

个模块的核心。WifiService 负责启动关闭 wpa_supplicant、启动关闭 WifiMonitor 监视线程

和把命令下发给 wpa_supplicant,而 WifiMonitor 则负责从 wpa_supplicant 接收事件通知。

连接 AP

1. 使能 WIFI

WirelessSettings 在初始化的时候配置了由 WifiEnabler 来处理 Wifi 按钮,

private void initToggles() {

mWifiEnabler =new WifiEnabler(

this,

(WifiManager) getSystemService(WIFI_SERVICE),

(CheckBoxPreference) findPreference(KEY_TOGGLE_WIFI));

当用户按下 Wifi 按钮后, Android 会调用 WifiEnabler 的 onPreferenceChange,

再由 WifiEnabler

调用 WifiManager 的 setWifiEnabled 接口函数,通过 AIDL,实际调用的是 WifiService 的

setWifiEnabled 函数,WifiService 接着向自身发送一条 MESSAGE_ENABLE_WIFI 消息,在

处理该消息的代码中做真正的使能工作:首先装载 WIFI 内核模块(该模块的位置硬编码为

"/system/lib/modules/wlan.ko" ), 然后启动 wpa_supplicant ( 配置文件硬编码为

"/data/misc/wifi/wpa_supplicant.conf") 再通过 WifiStateTracker 来启动 WifiMonitor 中的监视

线程。

private boolean setWifiEnabledBlocking(booleanenable) {

final int eventualWifiState = enable ? WIFI_STATE_ENABLED :

WIFI_STATE_DISABLED;

updateWifiState(enable ? WIFI_STATE_ENABLING : WIFI_STATE_DISABLING);

if (enable) {

if (!WifiNative.loadDriver()) {

Log.e(TAG, "Failed to load Wi-Fi driver.");

updateWifiState(WIFI_STATE_UNKNOWN);

return false;

}

if (!WifiNative.startSupplicant()) {

WifiNative.unloadDriver();

Log.e(TAG, "Failed to start supplicant daemon.");

updateWifiState(WIFI_STATE_UNKNOWN);

return false;

}

mWifiStateTracker.startEventLoop();

}

// Success!

persistWifiEnabled(enable);

updateWifiState(eventualWifiState);

return true;

}

当使能成功后,会广播发送 WIFI_STATE_CHANGED_ACTION 这个 Intent 通知外界 WIFI

已经成功使能了。 WifiEnabler 创建的时候就会向 Android 注册接收

WIFI_STATE_CHANGED_ACTION,因此它会收到该 Intent,从而开始扫描。

private voidhandleWifiStateChanged(int wifiState) {

if (wifiState == WIFI_STATE_ENABLED) {

loadConfiguredAccessPoints();

attemptScan();

}

2. 查找 AP

扫描的入口函数是 WifiService 的 startScan,它其实也就是往 wpa_supplicant 发送 SCAN 命

令。

static jboolean android_net_wifi_scanCommand(JNIEnv* env, jobject clazz)

{

jboolean result;

// Ignore any error from setting the scanmode.

// The scan will still work.

(void)doBooleanCommand("DRIVERSCAN-ACTIVE", "OK");

result =doBooleanCommand("SCAN", "OK");

(void)doBooleanCommand("DRIVERSCAN-PASSIVE", "OK");

return result;

}

当 wpa_supplicant 处理完 SCAN 命令后,它会向控制通道发送事件通知扫描完成,从而

wifi_wait_for_event 函数会接收到该事件,由此 WifiMonitor 中的 MonitorThread 会被执行来

出来这个事件,

void handleEvent(int event, String remainder) {

case SCAN_RESULTS:

mWifiStateTracker.notifyScanResultsAvailable();

break;

WifiStateTracker 则接着广播发送 SCAN_RESULTS_AVAILABLE_ACTION 这个 Intent

case EVENT_SCAN_RESULTS_AVAILABLE:

mContext.sendBroadcast(new

Intent(WifiManager.SCAN_RESULTS_AVAILABLE_ACTION));

WifiLayer 注册了接收SCAN_RESULTS_AVAILABLE_ACTION 这个 Intent,所以它的相关

处理函数handleScanResultsAvailable 会被调用,在该函数中,先会去拿到 SCAN 的结果(最

终是往 wpa_supplicant 发送 SCAN_RESULT 命令并读取返回值来实现的) ,

List<ScanResult> list = mWifiManager.getScanResults();

对每一个扫描返回的 AP,WifiLayer 会调用 WifiSettings 的 onAccessPointSetChanged 函数,

从而最终把该 AP 加到 GUI 显示列表中。

public voidonAccessPointSetChanged(AccessPointState ap, boolean added) {

AccessPointPreference pref = mAps.get(ap);

if (added) {

if (pref == null) {

pref = new AccessPointPreference(this, ap);

mAps.put(ap, pref);

} else {

pref.setEnabled(true);

}

mApCategory.addPreference(pref);

}

3. 配置 AP 参数

当用户在 WifiSettings 界面上选择了一个 AP 后,会显示配置 AP 参数的一个对话框,

public booleanonPreferenceTreeClick(PreferenceScreen preferenceScreen, Preference

preference) {

if (preferenceinstanceof AccessPointPreference) {

AccessPointState state = ((AccessPointPreference)

preference).getAccessPointState();

showAccessPointDialog(state, AccessPointDialog.MODE_INFO);

}

4. 连接

当用户在AcessPointDialog 中选择好加密方式和输入密钥之后,再点击连接按钮,Android

就会去连接这个 AP。

private void handleConnect() {

String password =getEnteredPassword();

if(!TextUtils.isEmpty(password)) {

mState.setPassword(password);

}

mWifiLayer.connectToNetwork(mState);

}

WifiLayer 会先检测这个 AP 是不是之前被配置过,这个是通过向 wpa_supplicant 发送

LIST_NETWORK 命令并且比较返回值来实现的,

// NeedWifiConfiguration for the AP

WifiConfigurationconfig = findConfiguredNetwork(state);

如果 wpa_supplicant 没有这个 AP 的配置信息, 则会向 wpa_supplicant 发送 ADD_NETWORK

命令来添加该 AP,

if (config ==null) {

// Connecting for the first time, need to create it

config = addConfiguration(state,

ADD_CONFIGURATION_ENABLE|ADD_CONFIGURATION_SAVE);

}

ADD_NETWORK 命令会返回一个 ID , WifiLayer 再用这个返回的 ID 作为参数向

wpa_supplicant 发送 ENABLE_NETWORK 命令,从而让 wpa_supplicant 去连接该 AP。

// Make sure thatnetwork is enabled, and disable others

mReenableApsOnNetworkStateChange = true;

if(!mWifiManager.enableNetwork(state.networkId, true)) {

Log.e(TAG, "Could not enable network ID " + state.networkId);

error(R.string.error_connecting);

return false;

}

5. 配置 IP 地址

当 wpa_supplicant 成功连接上 AP 之后,它会向控制通道发送事件通知连接上 AP 了,从而

wifi_wait_for_event 函数会接收到该事件,由此 WifiMonitor 中的 MonitorThread 会被执行来

出来这个事件,

voidhandleEvent(int event, String remainder) {

case CONNECTED:

handleNetworkStateChange(NetworkInfo.DetailedState.CONNECTED,

remainder);

break;

WifiMonitor 再调用WifiStateTracker 的notifyStateChange,WifiStateTracker 则接着会往自身

发送 EVENT_DHCP_START消息来启动 DHCP 去获取 IP 地址,

private void handleConnectedState() {

setPollTimer();

mLastSignalLevel= -1;

if(!mHaveIPAddress && !mObtainingIPAddress) {

mObtainingIPAddress = true;

mDhcpTarget.obtainMessage(EVENT_DHCP_START).sendToTarget();

}

然后再广播发送NETWORK_STATE_CHANGED_ACTION 这个 Intent

case EVENT_NETWORK_STATE_CHANGED:

if (result.state != DetailedState.DISCONNECTED || !mDisconnectPending) {

intent = new

Intent(WifiManager.NETWORK_STATE_CHANGED_ACTION);

intent.putExtra(WifiManager.EXTRA_NETWORK_INFO,

mNetworkInfo);

if (result.BSSID != null)

intent.putExtra(WifiManager.EXTRA_BSSID, result.BSSID);

mContext.sendStickyBroadcast(intent);

}

break;

WifiLayer 注册了接收NETWORK_STATE_CHANGED_ACTION 这个 Intent,所以它的相关

处理函数handleNetworkStateChanged 会被调用,

当 DHCP 拿到 IP 地址之后,会再发送EVENT_DHCP_SUCCEEDED 消息,

private class DhcpHandler extends Handler {

public voidhandleMessage(Message msg) {

switch (msg.what) {

case EVENT_DHCP_START:

if (NetworkUtils.runDhcp(mInterfaceName, mDhcpInfo)) {

event = EVENT_DHCP_SUCCEEDED;

}

WifiLayer 处理 EVENT_DHCP_SUCCEEDED 消息 , 会再次广播发送

NETWORK_STATE_CHANGED_ACTION 这个 Intent,这次带上完整的 IP 地址信息。

case EVENT_DHCP_SUCCEEDED:

mWifiInfo.setIpAddress(mDhcpInfo.ipAddress);

setDetailedState(DetailedState.CONNECTED);

intent =new Intent(WifiManager.NETWORK_STATE_CHANGED_ACTION);

intent.putExtra(WifiManager.EXTRA_NETWORK_INFO, mNetworkInfo);

mContext.sendStickyBroadcast(intent);

break;

至此为止,整个连接过程完成。

系统中对网络的判断和选在是在Connectivityervice这个服务中来处理的，在系统启动的时候会启动这个系统服务：

系统启动完毕后，ConnectivityService在系统启动的时候就启动了。

在android内部，用framework/base/core/res/res/values/config.xml中定义了网络的类型：

<string-array translatable="false"name="networkAttributes">

<item>"default,wifi,0"</item>

<item>"default,mobile,0"</item>

<item>"mms,mobile,1"</item>

<item>"supl,mobile,1"</item>

<item>"dun,mobile,1"</item>

<item>"hipri,mobile,2"</item>

</string-array>

<string-array translatable="false"name="radioAttributes">

<item>"mobile,0,1"</item>

</string-array>

ConnectivityManager定义了向对应的字符串常量：

public static final int TYPE_MOBILE = 0;

/**

* The Default WIFI data connection. Whenactive, all data traffic

* will use this connection by default. Should not coexist with other

* default connections.

public static final intTYPE_WIFI = 1;

/**

* An MMS-specific Mobile data connection. This connection may be the

* same as {@link #TYPEMOBILE} but itmay be different. This is used

* by applications needing to talk to thecarrier's Multimedia Messaging

* Service servers. It may coexist withdefault data connections.

* {@hide}

public static final int TYPE_MOBILE_MMS = 2;

/**

* A SUPL-specific Mobile data connection. This connection may be the

* same as {@link #TYPEMOBILE} but itmay be different. This is used

* by applications needing to talk to thecarrier's Secure User Plane

* Location servers for help locating thedevice. It may coexist with

* default data connections.

* {@hide}

public static final int TYPE_MOBILE_SUPL = 3;

/**

* A DUN-specific Mobile data connection. This connection may be the

* same as {@link #TYPEMOBILE} but itmay be different. This is used

* by applicaitons performing a Dial UpNetworking bridge so that

* the carrier is aware of DUN traffic. Itmay coexist with default data

* connections.

* {@hide}

public static final int TYPE_MOBILE_DUN = 4;

/**

* A High Priority Mobile data connection. This connection is typically

* the same as {@link #TYPEMOBILE} butthe routing setup is different.

* Only requesting processes will have access tothe Mobile DNS servers

* and only IP's explicitly requested via {@link #requestRouteToHost}

* will route over this interface.

*{@hide}

public static final int TYPE_MOBILE_HIPRI = 5;

/** {@hide}*/

public static final int MAX_RADIO_TYPE =TYPE_WIFI;

/** {@hide}*/

public static final int MAX_NETWORK_TYPE =TYPE_MOBILE_HIPRI;

public static final int DEFAULT_NETWORK_PREFERENCE =TYPE_WIFI;

并设置了默认的网络连接是TYPE_WIFI.

ConnectivityManager的方法是通过AIDL的使用，调用ConnectivityService中的方法来实现的。ConnectivityService继承了IConnectivityManage.stub.

在ConnectivityService内部，定义了两个类来解析xml中的网络类型，类的代码如下：

private class NetworkAttributes {

/**

* Class for holdingsettings read from resources.

public String mName;

public int mType;

public int mRadio;

public int mPriority;

public NetworkInfo.StatemLastState;

publicNetworkAttributes(String init) {

String fragments[] = init.split(",");

mName= fragments[0].toLowerCase();

if(fragments[1].toLowerCase().equals("wifi")) {

mRadio = ConnectivityManager.TYPE_WIFI;

}else {

mRadio = ConnectivityManager.TYPE_MOBILE;

}

if(mName.equals("default")) {

mType = mRadio;

}else if (mName.equals("mms")) {

mType = ConnectivityManager.TYPE_MOBILE_MMS;

}else if (mName.equals("supl")) {

mType = ConnectivityManager.TYPE_MOBILE_SUPL;

}else if (mName.equals("dun")) {

mType = ConnectivityManager.TYPE_MOBILE_DUN;

}else if (mName.equals("hipri")) {

mType = ConnectivityManager.TYPE_MOBILE_HIPRI;

}

mPriority = Integer.parseInt(fragments[2]);

mLastState = NetworkInfo.State.UNKNOWN;

}

public boolean isDefault() {

return(mType == mRadio);

}

private class RadioAttributes {

public String mName;

public int mPriority;

public int mSimultaneity;

public int mType;

public RadioAttributes(Stringinit) {

Stringfragments[] = init.split(",");

mName= fragments[0].toLowerCase();

mPriority = Integer.parseInt(fragments[1]);

mSimultaneity = Integer.parseInt(fragments[2]);

if(mName.equals("wifi")) {

mType = ConnectivityManager.TYPE_WIFI;

}else {

mType = ConnectivityManager.TYPE_MOBILE;

}

并通过一下代码，来给网络分配优先级，

mPriorityList = new int[naStrings.length];

{

int priority= 0; //lowest

intnextPos = naStrings.length-1;

while(nextPos>-1) {

for (int i = 0; i < mNetAttributes.length; i++) {

if(mNetAttributes[i].mPriority == priority) {

mPriorityList[nextPos--] = i;

}

priority++;

}

mNetRequestersPids =

new ArrayList[ConnectivityManager.MAX_NETWORK_TYPE+1];

for (int i=0; i<=ConnectivityManager.MAX_NETWORK_TYPE;i++) {

mNetRequestersPids[i] = new ArrayList();

}

其中，TYPE_MOBILE_HIPRI的优先级最高，其次为TYPE_MOBILE_MMS，TYPE_MOBILE_SUPL，TYPE_MOBILE_DUN，

优先级最低的为TYPE_WIFI，TYPE_MOBILE。TYPE_WIFI，TYPE_MOBILE两个网络类型中，TYPE_WIFI大于TYPE_MOBILE的优先级，

在打开wifi的连接后，mobile网络会被关闭。wifi网络连接关闭后，mobile网络会重新连接。在处理网络连接的Handler的代码中有处理：

private void handleConnect(NetworkInfo info) {

int type = info.getType();

Log.d(TAG, "Got NetworkConnection Succ from Driver nwtype="+type);

// snapshot isFailover,because sendConnectedBroadcast() resets it

boolean isFailover =info.isFailover();

NetworkStateTracker thisNet =mNetTrackers[type];

// if this is a default netand other default is running

// kill the one not preferred

if(mNetAttributes[type].isDefault()) {

if(mActiveDefaultNetwork != -1 && mActiveDefaultNetwork != type) {

if ((type != mNetworkPreference &&

mNetAttributes[mActiveDefaultNetwork].mPriority >

mNetAttributes[type].mPriority) ||

mNetworkPreference == mActiveDefaultNetwork) {

if(!((SystemProperties.get(CNE.UseCne,"false").equals("true")||

SystemProperties.get(CNE.UseCne,"false").equals("TRUE"))&&

CNE.isCndUp)) {

// don't accept this one

if (DBG) Log.v(TAG, "Not broadcasting CONNECT_ACTION " +

"to torn down network " + info.getTypeName());

teardown(thisNet);

}

return;

} else {

// tear down the other

NetworkStateTracker otherNet =

mNetTrackers[mActiveDefaultNetwork];

if (DBG) Log.v(TAG, "Policy requires " +

otherNet.getNetworkInfo().getTypeName() +

" teardown");

if(!((SystemProperties.get(CNE.UseCne,"false").equals("true")||

SystemProperties.get(CNE.UseCne,"false").equals("TRUE"))&&

CNE.isCndUp)) {

if (DBG) Log.i(TAG, "CNE To support Simultaneous Nws we"+

" will not tear down other nw");

if (!teardown(otherNet)) {

Log.e(TAG, "Network declined teardown request");

return;

}

if (isFailover) {

otherNet.releaseWakeLock();

}

mActiveDefaultNetwork = type;

}

thisNet.setTeardownRequested(false);

thisNet.updateNetworkSettings();

handleConnectivityChange();

sendConnectedBroadcast(info);

}

SystemServer启动ConnectivityService，ConnectivityService启动对网络的监视器。

在SystemServer的run()函数中，启动ConnectivityService的代码：

try {

Log.i(TAG, "Connectivity Service");

connectivity = ConnectivityService.getInstance(context);

ServiceManager.addService(Context.CONNECTIVITY_SERVICE, connectivity);

connectivity.startCne();

}catch (Throwable e) {

Log.e(TAG, "Failure starting Connectivity Service", e);

}

在ConnectivityService的构造函数中启动网络监视器的代码：

if (DBG) Log.v(TAG, "Starting Wifi Service.");

WifiStateTracker wst = newWifiStateTracker(context, mHandler);

WifiService wifiService = newWifiService(context, wst);

ServiceManager.addService(Context.WIFI_SERVICE, wifiService);

mNetTrackers[ConnectivityManager.TYPE_WIFI] = wst;

mNetTrackers[ConnectivityManager.TYPE_MOBILE] =

new MobileDataStateTracker(context, mHandler,

ConnectivityManager.TYPE_MOBILE, Phone.APN_TYPE_DEFAULT,

"MOBILE");

mNetTrackers[ConnectivityManager.TYPE_MOBILE_MMS] =

new MobileDataStateTracker(context, mHandler,

ConnectivityManager.TYPE_MOBILE_MMS, Phone.APN_TYPE_MMS,

"MOBILE_MMS");

mNetTrackers[ConnectivityManager.TYPE_MOBILE_SUPL] =

new MobileDataStateTracker(context, mHandler,

ConnectivityManager.TYPE_MOBILE_SUPL, Phone.APN_TYPE_SUPL,

"MOBILE_SUPL");

mNetTrackers[ConnectivityManager.TYPE_MOBILE_DUN] =

new MobileDataStateTracker(context, mHandler,

ConnectivityManager.TYPE_MOBILE_DUN, Phone.APN_TYPE_DUN,

"MOBILE_DUN");

mNetTrackers[ConnectivityManager.TYPE_MOBILE_HIPRI] =

new MobileDataStateTracker(context, mHandler,

ConnectivityManager.TYPE_MOBILE_HIPRI, Phone.APN_TYPE_HIPRI,

"MOBILE_HIPRI");

mNumDnsEntries = 0;

mTestMode =SystemProperties.get("cm.test.mode").equals("true")

&& SystemProperties.get("ro.build.type").equals("eng");

for (NetworkStateTracker t :mNetTrackers)

t.startMonitoring();

// Constructing this startsit too

mWifiWatchdogService = newWifiWatchdogService(context, wst);

在网络监视器中捕捉了settings中发出的相应的网络广播信息，

网络监视器中注册了settings中网络变化的信息，有变化会做相应的处理，并将处理的结果存储在NetworkInfo类的一个对象中，在ConnectivityService中通过

public NetworkInfogetNetworkInfo(int networkType)方法可以得知当前networkType类型网络的连接情况。

在app中，我们可以通过ConnectivityManager来获取当前的网络信息，并能指定当前程序需要的网络类型：

ConnectivityManager mCnn =context.getSystemService(context.NONNECTIVITY_SERVICE);

NetworkInfo mNetinfo =mCnn.getActiveNetworkInfo();

mCnn.setNetworkPreference(int preference);//设定首选网络类型。

假如没有设定，网络类型为系统默认。在wifi，3G网络同时存在的情况下，系统会默认的调用wifi网络，加载wifi的驱动，走wifi网络。

wifi子系统的分析：

初始化

在 SystemServer 启动的时候,会生成一个 ConnectivityService 的实例,

try {

Log.i(TAG, "Starting Connectivity Service.");

ServiceManager.addService(Context.CONNECTIVITY_SERVICE, new

ConnectivityService(context));

} catch (Throwable e) {

Log.e(TAG, "Failure starting Connectivity Service", e);

}

ConnectivityService 的构造函数会创建 WifiService,

if (DBG)Log.v(TAG, "Starting Wifi Service.");

mWifiStateTracker= new WifiStateTracker(context, handler);

WifiServicewifiService = new WifiService(context, mWifiStateTracker);

ServiceManager.addService(Context.WIFI_SERVICE, wifiService);

WifiStateTracker 会创建 WifiMonitor 接收来自底层的事件,WifiService 和 WifiMonitor 是整

个模块的核心。WifiService 负责启动关闭 wpa_supplicant、启动关闭 WifiMonitor 监视线程

和把命令下发给 wpa_supplicant,而 WifiMonitor 则负责从 wpa_supplicant 接收事件通知。

连接 AP

1. 使能 WIFI

WirelessSettings 在初始化的时候配置了由 WifiEnabler 来处理 Wifi 按钮,

private void initToggles() {

mWifiEnabler =new WifiEnabler(

this,

(WifiManager) getSystemService(WIFI_SERVICE),

(CheckBoxPreference) findPreference(KEY_TOGGLE_WIFI));

当用户按下 Wifi 按钮后, Android 会调用 WifiEnabler 的 onPreferenceChange,

再由 WifiEnabler

调用 WifiManager 的 setWifiEnabled 接口函数,通过 AIDL,实际调用的是 WifiService 的

setWifiEnabled 函数,WifiService 接着向自身发送一条 MESSAGE_ENABLE_WIFI 消息,在

处理该消息的代码中做真正的使能工作:首先装载 WIFI 内核模块(该模块的位置硬编码为

"/system/lib/modules/wlan.ko" ), 然后启动 wpa_supplicant ( 配置文件硬编码为

"/data/misc/wifi/wpa_supplicant.conf") 再通过 WifiStateTracker 来启动 WifiMonitor 中的监视

线程。

private boolean setWifiEnabledBlocking(booleanenable) {

final int eventualWifiState = enable ? WIFI_STATE_ENABLED :

WIFI_STATE_DISABLED;

updateWifiState(enable ? WIFI_STATE_ENABLING : WIFI_STATE_DISABLING);

if (enable) {

if (!WifiNative.loadDriver()) {

Log.e(TAG, "Failed to load Wi-Fi driver.");

updateWifiState(WIFI_STATE_UNKNOWN);

return false;

}

if (!WifiNative.startSupplicant()) {

WifiNative.unloadDriver();

Log.e(TAG, "Failed to start supplicant daemon.");

updateWifiState(WIFI_STATE_UNKNOWN);

return false;

}

mWifiStateTracker.startEventLoop();

}

// Success!

persistWifiEnabled(enable);

updateWifiState(eventualWifiState);

return true;

}

当使能成功后,会广播发送 WIFI_STATE_CHANGED_ACTION 这个 Intent 通知外界 WIFI

已经成功使能了。 WifiEnabler 创建的时候就会向 Android 注册接收

WIFI_STATE_CHANGED_ACTION,因此它会收到该 Intent,从而开始扫描。

private voidhandleWifiStateChanged(int wifiState) {

if (wifiState == WIFI_STATE_ENABLED) {

loadConfiguredAccessPoints();

attemptScan();

}

2. 查找 AP

扫描的入口函数是 WifiService 的 startScan,它其实也就是往 wpa_supplicant 发送 SCAN 命

令。

static jboolean android_net_wifi_scanCommand(JNIEnv* env, jobject clazz)

{

jboolean result;

// Ignore any error from setting the scanmode.

// The scan will still work.

(void)doBooleanCommand("DRIVERSCAN-ACTIVE", "OK");

result =doBooleanCommand("SCAN", "OK");

(void)doBooleanCommand("DRIVERSCAN-PASSIVE", "OK");

return result;

}

当 wpa_supplicant 处理完 SCAN 命令后,它会向控制通道发送事件通知扫描完成,从而

wifi_wait_for_event 函数会接收到该事件,由此 WifiMonitor 中的 MonitorThread 会被执行来

出来这个事件,

void handleEvent(int event, String remainder) {

case SCAN_RESULTS:

mWifiStateTracker.notifyScanResultsAvailable();

break;

WifiStateTracker 则接着广播发送 SCAN_RESULTS_AVAILABLE_ACTION 这个 Intent

case EVENT_SCAN_RESULTS_AVAILABLE:

mContext.sendBroadcast(new

Intent(WifiManager.SCAN_RESULTS_AVAILABLE_ACTION));

WifiLayer 注册了接收 SCAN_RESULTS_AVAILABLE_ACTION这个 Intent,所以它的相关

处理函数handleScanResultsAvailable 会被调用,在该函数中,先会去拿到 SCAN 的结果(最

终是往 wpa_supplicant 发送 SCAN_RESULT 命令并读取返回值来实现的) ,

List<ScanResult> list = mWifiManager.getScanResults();

对每一个扫描返回的 AP,WifiLayer 会调用 WifiSettings 的 onAccessPointSetChanged 函数,

从而最终把该 AP 加到 GUI 显示列表中。

public voidonAccessPointSetChanged(AccessPointState ap, boolean added) {

AccessPointPreference pref = mAps.get(ap);

if (added) {

if (pref == null) {

pref = new AccessPointPreference(this, ap);

mAps.put(ap, pref);

} else {

pref.setEnabled(true);

}

mApCategory.addPreference(pref);

}

3. 配置 AP 参数

当用户在 WifiSettings 界面上选择了一个 AP 后,会显示配置 AP 参数的一个对话框,

public booleanonPreferenceTreeClick(PreferenceScreen preferenceScreen, Preference

preference) {

if (preferenceinstanceof AccessPointPreference) {

AccessPointState state = ((AccessPointPreference)

preference).getAccessPointState();

showAccessPointDialog(state, AccessPointDialog.MODE_INFO);

}

4. 连接

当用户在 AcessPointDialog中选择好加密方式和输入密钥之后,再点击连接按钮,Android

就会去连接这个 AP。

private void handleConnect() {

String password =getEnteredPassword();

if(!TextUtils.isEmpty(password)) {

mState.setPassword(password);

}

mWifiLayer.connectToNetwork(mState);

}

WifiLayer 会先检测这个 AP 是不是之前被配置过,这个是通过向 wpa_supplicant 发送

LIST_NETWORK 命令并且比较返回值来实现的,

// NeedWifiConfiguration for the AP

WifiConfigurationconfig = findConfiguredNetwork(state);

如果 wpa_supplicant 没有这个 AP 的配置信息, 则会向 wpa_supplicant 发送 ADD_NETWORK

命令来添加该 AP,

if (config ==null) {

// Connecting for the first time, need to create it

config = addConfiguration(state,

ADD_CONFIGURATION_ENABLE|ADD_CONFIGURATION_SAVE);

}

ADD_NETWORK 命令会返回一个 ID , WifiLayer 再用这个返回的 ID 作为参数向

wpa_supplicant 发送 ENABLE_NETWORK 命令,从而让 wpa_supplicant 去连接该 AP。

// Make sure thatnetwork is enabled, and disable others

mReenableApsOnNetworkStateChange = true;

if(!mWifiManager.enableNetwork(state.networkId, true)) {

Log.e(TAG, "Could not enable network ID " + state.networkId);

error(R.string.error_connecting);

return false;

}

5. 配置 IP 地址

当 wpa_supplicant 成功连接上 AP 之后,它会向控制通道发送事件通知连接上 AP 了,从而

wifi_wait_for_event 函数会接收到该事件,由此 WifiMonitor 中的 MonitorThread 会被执行来

出来这个事件,

voidhandleEvent(int event, String remainder) {

case CONNECTED:

handleNetworkStateChange(NetworkInfo.DetailedState.CONNECTED,

remainder);

break;

WifiMonitor 再调用 WifiStateTracker的notifyStateChange,WifiStateTracker 则接着会往自身

发送EVENT_DHCP_START 消息来启动 DHCP 去获取 IP 地址,

private void handleConnectedState() {

setPollTimer();

mLastSignalLevel= -1;

if(!mHaveIPAddress && !mObtainingIPAddress) {

mObtainingIPAddress = true;

mDhcpTarget.obtainMessage(EVENT_DHCP_START).sendToTarget();

}

然后再广播发送NETWORK_STATE_CHANGED_ACTION 这个 Intent

case EVENT_NETWORK_STATE_CHANGED:

if (result.state != DetailedState.DISCONNECTED || !mDisconnectPending) {

intent = new

Intent(WifiManager.NETWORK_STATE_CHANGED_ACTION);

intent.putExtra(WifiManager.EXTRA_NETWORK_INFO,

mNetworkInfo);

if (result.BSSID != null)

intent.putExtra(WifiManager.EXTRA_BSSID, result.BSSID);

mContext.sendStickyBroadcast(intent);

}

break;

WifiLayer 注册了接收NETWORK_STATE_CHANGED_ACTION 这个 Intent,所以它的相关

处理函数handleNetworkStateChanged 会被调用,

当 DHCP 拿到 IP 地址之后,会再发送EVENT_DHCP_SUCCEEDED 消息,

private class DhcpHandler extends Handler {

public voidhandleMessage(Message msg) {

switch (msg.what) {

case EVENT_DHCP_START:

if (NetworkUtils.runDhcp(mInterfaceName, mDhcpInfo)) {

event = EVENT_DHCP_SUCCEEDED;

}

WifiLayer 处理 EVENT_DHCP_SUCCEEDED 消息 , 会再次广播发送

NETWORK_STATE_CHANGED_ACTION 这个 Intent,这次带上完整的 IP 地址信息。

case EVENT_DHCP_SUCCEEDED:

mWifiInfo.setIpAddress(mDhcpInfo.ipAddress);

setDetailedState(DetailedState.CONNECTED);

intent =new Intent(WifiManager.NETWORK_STATE_CHANGED_ACTION);

intent.putExtra(WifiManager.EXTRA_NETWORK_INFO, mNetworkInfo);

mContext.sendStickyBroadcast(intent);

break;

至此为止,整个连接过程完成。

(源自： http://blog.youkuaiyun.com/fengguowuhen7871/article/details/5849214)