簡單概況啟動過程

1.
WifiP2pService --- > WifiP2pServiceImpl

2.WifiP2pServiceImp構(gòu)造方法
    public WifiP2pServiceImpl(Context context) {
        mContext = context;

        mNetworkInfo = new NetworkInfo(ConnectivityManager.TYPE_WIFI_P2P, 0, NETWORKTYPE, "");

        mP2pSupported = mContext.getPackageManager().hasSystemFeature(
                PackageManager.FEATURE_WIFI_DIRECT);

        mThisDevice.primaryDeviceType = mContext.getResources().getString(
                com.android.internal.R.string.config_wifi_p2p_device_type);

        HandlerThread wifiP2pThread = new HandlerThread("WifiP2pService");
        wifiP2pThread.start();
        mClientHandler = new ClientHandler(wifiP2pThread.getLooper());

        mP2pStateMachine = new P2pStateMachine(TAG, wifiP2pThread.getLooper(), mP2pSupported);
        mP2pStateMachine.start();//狀態(tài)機
    }

前言

7.1 源碼
要看懂源碼旨巷，就需要深入了解狀態(tài)機(StateMachine)和雙Handler通信(AsyncChannel)

案例
WifiP2pManager.discoverPeers
客戶端：
1.看discoverPeers代碼

    public void discoverPeers(Channel c, ActionListener listener) {
        checkChannel(c);//檢測c是否存在巨缘，如果不存在，直接拋異常處理契沫。這也說明了带猴，channel首先被初始化的意義
        c.mAsyncChannel.sendMessage(DISCOVER_PEERS, 0, c.putListener(listener));
    }
    
   private static void checkChannel(Channel c) {
        if (c == null) throw new IllegalArgumentException("Channel needs to be initialized");
    }
    
    看wifi和藍(lán)牙代碼，必定涉及StateMachine懈万，同時也會涉及Handler跨進程通信(AsyncChannel)

2.c.mAsyncChannel

mAsyncChannel是Handler跨進程通信的關(guān)鍵類拴清。也就是說，三方應(yīng)用和WifiP2pService服務(wù)進行跨進程通信的實現(xiàn)方式就是采用Handler会通。了解了這些口予，則明白為什么要initialize，并且要傳入Looper對象

public Channel initialize(Context srcContext, Looper srcLooper, ChannelListener listener)

3.c.putListener(listener)

這種回調(diào)方法的處理方式涕侈，確實給人眼前一亮

        private int putListener(Object listener) {//返回值為key
            if (listener == null) return INVALID_LISTENER_KEY;
            int key;
            synchronized (mListenerMapLock) {
                do {
                    key = mListenerKey++;
                } while (key == INVALID_LISTENER_KEY);
                mListenerMap.put(key, listener);//把listener放在map中沪停。
            }
            return key;
        }
        //private HashMap<Integer, Object> mListenerMap = new HashMap<Integer, Object>();
也就是說，在Handler通信中裳涛，把listener轉(zhuǎn)化成arg2發(fā)送出去

4.sticky broadcast的使用:
系統(tǒng)發(fā)送sticky 廣播后木张，app才注冊此廣播，是否可以接收到廣播端三？
答案：能舷礼。具體原理，我們這里不分析郊闯。

    private void sendP2pStateChangedBroadcast(boolean enabled) {
        logd(Debug.getCallers(5));
        final Intent intent = new Intent(WifiP2pManager.WIFI_P2P_STATE_CHANGED_ACTION);
        intent.addFlags(Intent.FLAG_RECEIVER_REGISTERED_ONLY_BEFORE_BOOT);
        if (enabled) {
            intent.putExtra(WifiP2pManager.EXTRA_WIFI_STATE,
                    WifiP2pManager.WIFI_P2P_STATE_ENABLED);
        } else {
            intent.putExtra(WifiP2pManager.EXTRA_WIFI_STATE,
                    WifiP2pManager.WIFI_P2P_STATE_DISABLED);
        }
        mContext.sendStickyBroadcastAsUser(intent, UserHandle.ALL);
    }
    
    這也就是為什么妻献，我們注冊：WIFI_P2P_THIS_DEVICE_CHANGED_ACTION蛛株、WIFI_P2P_DISCOVERY_CHANGED_ACTION、WIFI_P2P_STATE_CHANGED_ACTION育拨、WIFI_P2P_CONNECTION_CHANGED_ACTION谨履，啟動app之后，會立馬接收到的原因

系統(tǒng)服務(wù)
1.WifiP2pServiceImpl

先要回答一個問題：WifiP2pServiceImpl中的狀態(tài)機熬丧，在客戶端調(diào)用之前笋粟，已經(jīng)處于什么狀態(tài)？
如果wifi是打開的析蝴，則處于InactiveState矗钟。
具體原因：
先說思路
1)WifiP2pServiceImpl和WifiStateMachine是有聯(lián)動的，也是通過handler通信
a.WifiStateMachine中的mWifiP2pChannel為聯(lián)動的變量
b.WifiStateMachine中的mP2pSupported為關(guān)鍵變量

2)WifiP2pServiceImpl和WifiMonitor是有聯(lián)動的嫌变，在構(gòu)造方法中
WifiP2pServiceImpl.P2pStateMachine構(gòu)造方法中使用如下：
    mWifiMonitor.registerHandler(interfaceName,
        WifiMonitor.AP_STA_CONNECTED_EVENT, getHandler());

2.回到狀態(tài)機

InactiveState沒有處理消息DISCOVER_PEERS，傳給了父狀態(tài)P2pEnabledState躬它，關(guān)注核心點：
                case WifiP2pManager.DISCOVER_PEERS:
                    if (mDiscoveryBlocked) {
                        replyToMessage(message, WifiP2pManager.DISCOVER_PEERS_FAILED,
                                WifiP2pManager.BUSY);
                        break;
                    }
                    // do not send service discovery request while normal find operation.
                    clearSupplicantServiceRequest();
                    if (mWifiNative.p2pFind(DISCOVER_TIMEOUT_S)) {//調(diào)用jni腾啥。注意：通過WifiMonitor回復(fù)WifiMonitor.P2P_DEVICE_FOUND_EVENT
                        replyToMessage(message, WifiP2pManager.DISCOVER_PEERS_SUCCEEDED);//客戶端調(diào)用的回調(diào)回復(fù)
                        sendP2pDiscoveryChangedBroadcast(true);//發(fā)送廣播，開始掃描發(fā)現(xiàn)對等設(shè)備
                    } else {
                        replyToMessage(message, WifiP2pManager.DISCOVER_PEERS_FAILED,
                                WifiP2pManager.ERROR);
                    }
                    break;


                case WifiMonitor.P2P_DEVICE_FOUND_EVENT://執(zhí)行jni層冯吓，底層給的回復(fù)
                    WifiP2pDevice device = (WifiP2pDevice) message.obj;
                    if (mThisDevice.deviceAddress.equals(device.deviceAddress)) break;
                    mPeers.updateSupplicantDetails(device);
                    sendPeersChangedBroadcast();//發(fā)送廣播倘待，帶有掃描到的設(shè)備

總結(jié)

1.discoverPeers(Channel c, ActionListener listener)的回調(diào)僅僅是判斷是否jni執(zhí)行成功
2.執(zhí)行成功，涉及需要進一步掃描設(shè)備组贺，所以通過廣播把數(shù)據(jù)報告出來凸舵，而不是通過回調(diào)
總之，回調(diào)的是執(zhí)行狀態(tài)失尖，結(jié)果通過廣播通知

案例
connect

android.net.wifi.p2p.PEERS_CHANGED
android.net.wifi.p2p.DISCOVERY_STATE_CHANGE
android.net.wifi.p2p.PEERS_CHANGED
android.net.wifi.p2p.THIS_DEVICE_CHANGED
android.net.wifi.p2p.CONNECTION_STATE_CHANGE
android.net.wifi.p2p.PEERS_CHANGED

額外發(fā)現(xiàn)

1.日志格式
        if (DBG) log("halfConnectSync srcHandler to the dstMessenger  E");

        // We are connected
        connected(srcContext, srcHandler, dstMessenger);

        if (DBG) log("halfConnectSync srcHandler to the dstMessenger X");
        
        為什么用E X
        想一下execute這個單詞
        
2.WifiP2pServiceImp和WifiStateMachine關(guān)聯(lián)啊奄？
兩者之間也通過雙handler通信

05-19 13:12:35.216   414   414 I WifiP2pService: Registering wifip2p
05-19 13:12:35.216   414   486 D WifiP2pService: P2pDisabledState
05-19 13:12:35.243   414   486 D WifiP2pService: P2pDisabledState what 69633
05-19 13:12:35.243   414   486 D WifiP2pService: DefaultState what 69633
05-19 13:12:35.243   414   486 D WifiP2pService: P2pDisabledState what 69632
05-19 13:12:35.243   414   486 D WifiP2pService: DefaultState what 69632
05-19 13:12:35.243   414   486 D WifiP2pService: Full connection with WifiStateMachine established
05-19 13:12:38.160   414   486 D WifiP2pService: P2pDisabledState what 131203 //CMD_ENABLE_P2P
05-19 13:12:38.177   414   486 E WifiP2pService: Unable to change interface settings: java.lang.IllegalStateException: command '25 interface setcfg p2p0 0.0.0.0 0 up' failed with '400 25 Failed to clear address (No such device)'
05-19 13:12:38.177   414   486 D WifiP2pService: P2pEnablingState
05-19 13:12:38.177   414   486 D WifiP2pService: P2pEnablingState what 147457  //SUP_CONNECTION_EVENT
05-19 13:12:38.177   414   486 D WifiP2pService: P2p socket connection successful

問題

1.mWifiP2pManager.listen用來做什么？

2.mWifiP2pManager.createGroup 怎么使用掀潮？

3.mWifiP2pManager.setDeviceName  是否可以默認(rèn)菇夸？ -- 可以，更改SettingsProvider即可

    private String getPersistedDeviceName() {
        String deviceName = Settings.Global.getString(mContext.getContentResolver(),
                Settings.Global.WIFI_P2P_DEVICE_NAME);
        if (deviceName == null) {
            /* We use the 4 digits of the ANDROID_ID to have a friendly
             * default that has low likelihood of collision with a peer */
            String id = Settings.Secure.getString(mContext.getContentResolver(),
                    Settings.Secure.ANDROID_ID);
            return "Android_" + id.substring(0,4);
        }
        return deviceName;
    }

    private boolean setAndPersistDeviceName(String devName) {
        if (devName == null) return false;

        if (!mWifiNative.setDeviceName(devName)) {
            loge("Failed to set device name " + devName);
            return false;
        }

        mThisDevice.deviceName = devName;
        mWifiNative.setP2pSsidPostfix("-" + mThisDevice.deviceName);

        Settings.Global.putString(mContext.getContentResolver(),
                Settings.Global.WIFI_P2P_DEVICE_NAME, devName);
        sendThisDeviceChangedBroadcast();
        return true;
    }
    
    第一次初始化
    private void initializeP2pSettings() {
        mWifiNative.setPersistentReconnect(true);
        mThisDevice.deviceName = getPersistedDeviceName();//初始化
        mWifiNative.setDeviceName(mThisDevice.deviceName);//設(shè)置1
        // DIRECT-XY-DEVICENAME (XY is randomly generated)
        mWifiNative.setP2pSsidPostfix("-" + mThisDevice.deviceName);//設(shè)置2
        mWifiNative.setDeviceType(mThisDevice.primaryDeviceType);
        // Supplicant defaults to using virtual display with display
        // which refers to a remote display. Use physical_display
        mWifiNative.setConfigMethods("virtual_push_button physical_display keypad");
        // STA has higher priority over P2P
        mWifiNative.setConcurrencyPriority("sta");

        mThisDevice.deviceAddress = mWifiNative.p2pGetDeviceAddress();
        updateThisDevice(WifiP2pDevice.AVAILABLE);//廣播更新狀態(tài)
        if (DBG) logd("DeviceAddress: " + mThisDevice.deviceAddress);

        mClientInfoList.clear();
        mWifiNative.p2pFlush();
        mWifiNative.p2pServiceFlush();
        mServiceTransactionId = 0;
        mServiceDiscReqId = null;

        updatePersistentNetworks(RELOAD);
    }