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Android4.4.2源码分析之WiFi模块(二)

时间:2016-05-11 11:28:16      阅读:241      评论:0      收藏:0      [点我收藏+]

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接着上一篇继续对WiFi源码的分析

Android4.4.2源码分析之WiFi模块(一)

onResume方法中

6>,首先是调用WiFiEnabler的resume方法对switch进行管理

接下来注册广播

getActivity().registerReceiver(mReceiver, mFilter);

广播监听的action如下

       //wifi状态改变的action
        mFilter.addAction(WifiManager.WIFI_STATE_CHANGED_ACTION);
       
       //WiFi扫描到附近可用WiFi时的广播
        mFilter.addAction(WifiManager.SCAN_RESULTS_AVAILABLE_ACTION);
      
       //
        mFilter.addAction(WifiManager.NETWORK_IDS_CHANGED_ACTION);
        mFilter.addAction(WifiManager.SUPPLICANT_STATE_CHANGED_ACTION);
        mFilter.addAction(WifiManager.CONFIGURED_NETWORKS_CHANGED_ACTION);
        mFilter.addAction(WifiManager.LINK_CONFIGURATION_CHANGED_ACTION);
        mFilter.addAction(WifiManager.NETWORK_STATE_CHANGED_ACTION);
        mFilter.addAction(WifiManager.RSSI_CHANGED_ACTION);

查看WiFiManager发现各action定义如下,以及在监听到对应广播后各处理如下

i>

 /**
     * Broadcast intent action indicating that Wi-Fi has been enabled, disabled,
     * enabling, disabling, or unknown. One extra provides this state as an int.
     * Another extra provides the previous state, if available.
     *
     * @see #EXTRA_WIFI_STATE
     * @see #EXTRA_PREVIOUS_WIFI_STATE
     */
    @SdkConstant(SdkConstantType.BROADCAST_INTENT_ACTION)
    public static final String WIFI_STATE_CHANGED_ACTION =
        "android.net.wifi.WIFI_STATE_CHANGED";

WIFI_STATE_CHANGED_ACTION:当WiFi被打开、关闭、正在打开、正在关闭或者位置状态即wifi状态发生改变时系统会自动发送该广播,该广播会附带有两个值,一个是int型表示改变后的state,可通过字段EXTRA_WIFI_STATE获取,还有一个是int型的改变前的state(如果有的话)可通过字段EXTRA_PREVIOUS_WIFI_STATE获取

当监听到该广播后会进行如下处理:更新WiFi状态(在WiFiEnbabler中也监听了该广播,用于当WiFi状态改变时对switch进行更新)

 if (WifiManager.WIFI_STATE_CHANGED_ACTION.equals(action)) {
            updateWifiState(intent.getIntExtra(WifiManager.EXTRA_WIFI_STATE,
                    WifiManager.WIFI_STATE_UNKNOWN));

updateWifiState方法如下

private void updateWifiState(int state) {
        Activity activity = getActivity();
        if (activity != null) {
        //重新加载菜单  ,该方法会调用activity中的onCreateOptionsMenu加载actionbar
         activity.invalidateOptionsMenu();
        }

        switch (state) {
            case WifiManager.WIFI_STATE_ENABLED://打开WiFi
              mScanner.resume();//从下面的方法中可以看到,该方法是用于开启WiFi的扫描,并记录扫描次数
                return; // not break, to avoid the call to pause() below

            case WifiManager.WIFI_STATE_ENABLING://正在打开WiFi
                addMessagePreference(R.string.wifi_starting);
                break;

            case WifiManager.WIFI_STATE_DISABLED://关闭WiFi
              //用户可以在wlan-->高级选项中去设置时是否随时都可以扫描(关闭WiFi后也可以扫描),根据用户的选择,
               //设置在关闭WLAN后显示界面上的文本
              setOffMessage();
                break;
        }

        mLastInfo = null;
        mLastState = null;
        mScanner.pause();//移除message通知
    }

因为更新的方法中涉及到了Scanner,这里的Scanner是自定义的内部类,继承自handler,代码如下

private class Scanner extends Handler {
        private int mRetry = 0;

        void resume() {
            if (!hasMessages(0)) {
                sendEmptyMessage(0);
            }
        }

        void forceScan() {
            removeMessages(0);
            sendEmptyMessage(0);
        }

        void pause() {
            mRetry = 0;
            removeMessages(0);
        }

        @Override
        public void handleMessage(Message message) {
            if (mWifiManager.startScan()) {
                mRetry = 0;
            } else if (++mRetry >= 3) {
                mRetry = 0;
                Activity activity = getActivity();
                if (activity != null) {
                    Toast.makeText(activity, R.string.wifi_fail_to_scan,
                            Toast.LENGTH_LONG).show();
                }
                return;
            }
            sendEmptyMessageDelayed(0, 10*1000);//10s后再次发送message
        }
    }

可以看到,扫描附近可用WiFi的方法为mWifiManager.startScan()该方法对用户可见,可直接调用

ii>

/**
     * An access point scan has completed, and results are available from the supplicant.
     * Call {@link #getScanResults()} to obtain the results.
     */
    @SdkConstant(SdkConstantType.BROADCAST_INTENT_ACTION)
    public static final String SCAN_RESULTS_AVAILABLE_ACTION = "android.net.wifi.SCAN_RESULTS";
SCAN_RESULT_AVAILABLE_ACTION:WiFi扫描结束时系统会发送该广播,用户可以监听该广播通过调用WifiManager的getScanResults方法来获取到扫描结果

else if (WifiManager.SCAN_RESULTS_AVAILABLE_ACTION.equals(action) ||
                WifiManager.CONFIGURED_NETWORKS_CHANGED_ACTION.equals(action) ||
                WifiManager.LINK_CONFIGURATION_CHANGED_ACTION.equals(action)) {
                updateAccessPoints();

当用户扫描到WiFi或者WiFi信息发生改变时都需要去更新WiFi列表,更新WiFi列表的方法为updateAccessPoints(),扫描加载列表这块感觉相当复杂,慢慢分析

首先在扫描结束后可以通过getScanResult()获取到扫描后的WiFi列表,返回值为List<ScanResult>,所返回的每个WiFi会携带如下信息

技术分享


各字段分别代表什么含义呢?

BSSID:The address of the access point,接入点地址(String值)

SSID:The network name,WiFi名字(String值)

capabilities:Describes the authentication,key management,and encryption schemes supported by the access point,描述接入点的身份验证,密钥管理和加密方案(String值)

wifiSsid:ASCII encode SSID,This will replace SSID when we deprecate it ,SSID的ASCII码编码,当不支持它时我们可以用它来代替ssid(WifiSsid值)

timestamp:timestamp in microseconds (since boot)when this result was last seen,距离上一次的更改的微秒数

level:对于level的定义从源码中可以看到,表示信号的强度,属于int型数值,

 /**
     * The detected signal level in dBm, also known as the RSSI.
     *
     * <p>Use {@link android.net.wifi.WifiManager#calculateSignalLevel} to convert this number into
     * an absolute signal level which can be displayed to a user.
     */
    public int level;

对于信号强度的显示可以通过如下代码

mWifiLevel.setImageLevel(WifiManager.calculateSignalLevel(mList.get(position).level,4));

frequency:The primary 20 MHz frequency (in MHz) of the channel over which the client is communicating with the access point.客户端与接入点通信的频率

我们一般显示WiFi列表用到的是SSID、level和capabilities


Android源码中扫描到WiFi后就需要去加载列表,在接收到SCAN_RESULT_AVAILABLE_ACTION广播后调用updateAccessPoints方法进行更新列表,在该方法中会根据WiFi的开关状态来对UI进行更新,只有在WiFi开启时 才会去更新列表,这里不再对其他情况进行赘述,在WiFi开启时会通过如下代码加载

 private void updateAccessPoints() {
        // Safeguard from some delayed event handling
        if (getActivity() == null) return;

        if (isRestrictedAndNotPinProtected()) {
            addMessagePreference(R.string.wifi_empty_list_user_restricted);
            return;
        }
        final int wifiState = mWifiManager.getWifiState();

        switch (wifiState) {
            case WifiManager.WIFI_STATE_ENABLED:
                // AccessPoints are automatically sorted with TreeSet.
                //获取到接入点列表
               final Collection<AccessPoint> accessPoints = constructAccessPoints();
                if (!getResources().getBoolean(R.bool.set_wifi_priority)) {
                    getPreferenceScreen().removeAll();
                }
                if(accessPoints.size() == 0) {
                    addMessagePreference(R.string.wifi_empty_list_wifi_on);
                }
                if (!getResources().getBoolean(R.bool.set_wifi_priority)) {
                   for (AccessPoint accessPoint : accessPoints) {
                       <pre name="code" class="java">                  
      //WiFisettings的xml文件的根节点为preferencescreen,所以通过如下方法添加
      preferencegetPreferenceScreen().addPreference(accessPoint); } } 
if (accessPoints.isEmpty()){ addMessagePreference(R.string.wifi_empty_list_wifi_on); } 
break; case WifiManager.WIFI_STATE_ENABLING://如果WiFi处于正在打开的状态,则清除列表 。。。。。。。。。 } }



那么接入点列表的获取是如何进行的呢?

 private List<AccessPoint> constructAccessPoints() {
        ArrayList<AccessPoint> accessPoints = new ArrayList<AccessPoint>();
        /** Lookup table to more quickly update AccessPoints by only considering objects with the
         * correct SSID.  Maps SSID -> List of AccessPoints with the given SSID.  */
          //key为ssid,value为接入点ScanResult
      Multimap<String, AccessPoint> apMap = new Multimap<String, AccessPoint>();

        if (getResources().getBoolean(R.bool.set_wifi_priority)) {
            emptyCategory();
        }
      //getConfiguredNetwors可以返回一个配置列表,获取到配置好的网络连接,该列表存放了关于已经连接过的接入点WiFi的信息,
          //返回的列表中包括如下字段,当WiFi 关闭时会返回null
           <pre name="code" class="java">         /** <ul>
          * <li>networkId</li>
          * <li>SSID</li>
          * <li>BSSID</li>
          * <li>priority</li>
          * <li>allowedProtocols</li>
          * <li>allowedKeyManagement</li>
          * <li>allowedAuthAlgorithms</li>
          * <li>allowedPairwiseCiphers</li>
          * <li>allowedGroupCiphers</li>
          * </ul>
          */
final List<WifiConfiguration> configs = mWifiManager.getConfiguredNetworks();
        if (configs != null) {
            for (WifiConfiguration config : configs) {
                if (config.SSID != null) {
                    AccessPoint accessPoint = new AccessPoint(getActivity(), config);
                    accessPoint.update(mLastInfo, mLastState);
                    accessPoints.add(accessPoint);
                    apMap.put(accessPoint.ssid, accessPoint);
                    if (getResources().getBoolean(R.bool.set_wifi_priority)) {
                        SetAPCategory(accessPoint, mConfigedAP);
                    }
                }
            }
            if (getResources().getBoolean(R.bool.set_wifi_priority)) {
                if (mConfigedAP != null && mConfigedAP.getPreferenceCount() == 0) {
                    getPreferenceScreen().removePreference(mConfigedAP);
                }
            }
        }

         //获取到WiFi扫描结果,返回附近可用WiFi,包括已经连接的或者已经保存的WiFi
        final List<ScanResult> results = mWifiManager.getScanResults();
        if (results != null) {
            for (ScanResult result : results) {
                // Ignore hidden and ad-hoc networks.
                if (result.SSID == null || result.SSID.length() == 0 ||
                        result.capabilities.contains("[IBSS]")) {
                    continue;
                }

                boolean found = false;
                for (AccessPoint accessPoint : apMap.getAll(result.SSID)) {
                    if (accessPoint.update(result))
                        found = true;
                }
                if (!found) {
                    AccessPoint accessPoint = new AccessPoint(getActivity(), result);
                    accessPoints.add(accessPoint);
                    apMap.put(accessPoint.ssid, accessPoint);
                    if (getResources().getBoolean(R.bool.set_wifi_priority)) {
                        SetAPCategory(accessPoint, mUnKnownAP);
                    }
                }
            }
            if (getResources().getBoolean(R.bool.set_wifi_priority)) {
                if(mUnKnownAP !=null && mUnKnownAP.getPreferenceCount() == 0){
                    getPreferenceScreen().removePreference(mUnKnownAP);
                }
            }
        }

        // Pre-sort accessPoints to speed preference insertion
        Collections.sort(accessPoints);
        return accessPoints;
    }


调用mWifiManager.getConfigureNetworks()方法获取到的是已经配置过连接过的WiFi列表,列表包含下列值


技术分享


对于扫描到的WiFi的保护方式通过判断scanresult的capabilities字段是否包含对应的string来判断属于何种保护方式

 boolean wpa = result.capabilities.contains("WPA-PSK");
        boolean wpa2 = result.capabilities.contains("WPA2-PSK")



iii>

/**
     * The network IDs of the configured networks could have changed.
     */
    @SdkConstant(SdkConstantType.BROADCAST_INTENT_ACTION)
    public static final String NETWORK_IDS_CHANGED_ACTION = "android.net.wifi.NETWORK_IDS_CHANGED";
NETWORK_IDS_CHANGED:所配置的网络的网络ID可能已经改变


iv>

  /**
     * Broadcast intent action indicating that the state of establishing a connection to
     * an access point has changed.One extra provides the new
     * {@link SupplicantState}. Note that the supplicant state is Wi-Fi specific, and
     * is not generally the most useful thing to look at if you are just interested in
     * the overall state of connectivity.
     * @see #EXTRA_NEW_STATE
     * @see #EXTRA_SUPPLICANT_ERROR
     */
    @SdkConstant(SdkConstantType.BROADCAST_INTENT_ACTION)
    public static final String SUPPLICANT_STATE_CHANGED_ACTION =
        "android.net.wifi.supplicant.STATE_CHANGE";


SUPPLICANT_STATE_CHANGED_ACTION:正在建立的连接状态已经改变,该广播会携带两个值


v>

 /**
     * Broadcast intent action indicating that the configured networks changed.
     * This can be as a result of adding/updating/deleting a network. If
     * {@link #EXTRA_MULTIPLE_NETWORKS_CHANGED} is set to true the new configuration
     * can be retreived with the {@link #EXTRA_WIFI_CONFIGURATION} extra. If multiple
     * Wi-Fi configurations changed, {@link #EXTRA_WIFI_CONFIGURATION} will not be present.
     * @hide
     */
    public static final String CONFIGURED_NETWORKS_CHANGED_ACTION =
        "android.net.wifi.CONFIGURED_NETWORKS_CHANGE";

CONFIGURED_NETWORKS_CHANGED_ACTION:当WiFi列表中的网络添加、更新或者删除时系统会发送该广播,但是该广播对用户隐藏,无法调用


vi>

/**
     * Broadcast intent action indicating that the state of Wi-Fi connectivity
     * has changed. One extra provides the new state
     * in the form of a {@link android.net.NetworkInfo} object. If the new
     * state is CONNECTED, additional extras may provide the BSSID and WifiInfo of
     * the access point.
     * as a {@code String}.
     * @see #EXTRA_NETWORK_INFO
     * @see #EXTRA_BSSID
     * @see #EXTRA_WIFI_INFO
     */
    @SdkConstant(SdkConstantType.BROADCAST_INTENT_ACTION)
    public static final String NETWORK_STATE_CHANGED_ACTION = "android.net.wifi.STATE_CHANGE";


NETWORK_STATE_CHANGED_ACTION:WiFi连接发生改变时系统会发送该广播,通过字段EXTRA_NETWORK_INFO可以获取到WiFi连接的状态,如果是已连接的状态,则会有额外的两个字段,字段EXTRA_BSSID可以获取到所连接的WiFi的bssid,字段EXTRA_WIFI_INFO可以获取到所连接的WiFi的信息获取到wifiinfo实例


vii>

 /**
     * The RSSI (signal strength) has changed.
     * @see #EXTRA_NEW_RSSI
     */
    @SdkConstant(SdkConstantType.BROADCAST_INTENT_ACTION)
    public static final String RSSI_CHANGED_ACTION = "android.net.wifi.RSSI_CHANGED";

WIFI_RSSI_CHANGED:当WiFi信号强度发生改变时系统会发送该广播,通过字段EXTRA_NEW_RSSI可以获取到改变后的wifi信号强度,当然也需要去更新WiFi列表



Android4.4.2源码分析之WiFi模块(二)

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原文地址:http://blog.csdn.net/zrf1335348191/article/details/51351895

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