Android之WIFI-WifiMonitor分析

概述

WifiMonitor负责监听wpa_supplicant发送的数据，并将数据分发给个监听者

详细
1.怎么监听wpa_supplicant发送过来的数据

    private class MonitorThread extends Thread {
        private final LocalLog mLocalLog;

        public MonitorThread(LocalLog localLog) {
            super("WifiMonitor");
            mLocalLog = localLog;
        }

        public void run() {
            if (DBG) {
                Log.d(TAG, "MonitorThread start with mConnected=" + mConnected);
            }
            //noinspection InfiniteLoopStatement
            for (;;) {
                if (!mConnected) {
                    if (DBG) Log.d(TAG, "MonitorThread exit because mConnected is false");
                    break;
                }
                String eventStr = mWifiNative.waitForEvent();//监听wpa_supplicant发送的数据

                // Skip logging the common but mostly uninteresting events
                if (!eventStr.contains(BSS_ADDED_STR) && !eventStr.contains(BSS_REMOVED_STR)) {
                    if (DBG) Log.d(TAG, "Event [" + eventStr + "]");
                    mLocalLog.log("Event [" + eventStr + "]");
                }

                if (dispatchEvent(eventStr)) {
                    if (DBG) Log.d(TAG, "Disconnecting from the supplicant, no more events");
                    break;
                }
            }
        }
    }

2.怎么将数据分发给监听者?
1)监听者是怎么注册进来的？

    private final Map<String, SparseArray<Set<Handler>>> mHandlerMap = new HashMap<>();
    
    public synchronized void registerHandler(String iface, int what, Handler handler) {
        SparseArray<Set<Handler>> ifaceHandlers = mHandlerMap.get(iface);
        if (ifaceHandlers == null) {
            ifaceHandlers = new SparseArray<>();
            mHandlerMap.put(iface, ifaceHandlers);
        }
        Set<Handler> ifaceWhatHandlers = ifaceHandlers.get(what);
        if (ifaceWhatHandlers == null) {
            ifaceWhatHandlers = new ArraySet<>();
            ifaceHandlers.put(what, ifaceWhatHandlers);
        }
        ifaceWhatHandlers.add(handler);
    }
    1)mHandlerMap是一个map。key\values，这个values是数组SparseArray<Set<Handler>>
    2)SparseArray<Set<Handler>>是一个数组。kyes\values，这个values是集合Set<Handler>
    
    这是三维代码。通过iface获取数组SparseArray，通过what获取handler集合。关键是监听者的handler做数据处理。也就是说，一个what不仅仅对应一个handler，而是对应多个handler

2)监听者处理数据

MonitorThread.run调用了dispatchEvent

    private synchronized boolean dispatchEvent(String eventStr) {
        ······
        if (dispatchEvent(eventStr, iface)) {
            mConnected = false;
            return true;
        }
        return false;
    }
    
    private boolean dispatchEvent(String eventStr, String iface) {
        //1.根据eventStr和iface过滤有效数据
        //2.关键点为sendMessage
    }
    
    private void sendMessage(String iface, Message message) {
        SparseArray<Set<Handler>> ifaceHandlers = mHandlerMap.get(iface);//从mHandlerMap中获取iface数组
        if (iface != null && ifaceHandlers != null) {
            if (isMonitoring(iface)) {
                boolean firstHandler = true;
                Set<Handler> ifaceWhatHandlers = ifaceHandlers.get(message.what);//数组存在，则通过what获取handler集合
                if (ifaceWhatHandlers != null) {
                    for (Handler handler : ifaceWhatHandlers) {//集中处理handler集合
                        if (firstHandler) {
                            firstHandler = false;
                            sendMessage(handler, message);
                        }
                        else {
                            sendMessage(handler, Message.obtain(message));
                        }
                    }
                }
            } else {
                if (DBG) Log.d(TAG, "Dropping event because (" + iface + ") is stopped");
            }
        } else {
            if (DBG) Log.d(TAG, "Sending to all monitors because there's no matching iface");
            boolean firstHandler = true;
            for (Map.Entry<String, SparseArray<Set<Handler>>> entry : mHandlerMap.entrySet()) {
                if (isMonitoring(entry.getKey())) {
                    Set<Handler> ifaceWhatHandlers = entry.getValue().get(message.what);
                    for (Handler handler : ifaceWhatHandlers) {
                        if (firstHandler) {
                            firstHandler = false;
                            sendMessage(handler, message);
                        }
                        else {
                            sendMessage(handler, Message.obtain(message));
                        }
                    }
                }
            }
        }
    }

    private void sendMessage(Handler handler, Message message) {
        if (handler != null) {
            message.setTarget(handler);//设置目标对象
            message.sendToTarget();//发送给目标对象
        }
    }

总结

1.我们一般设置回调时，就是调用监听者的回调方法，而这里的监听处理就显着与众不同
2.因为它回调给的是目标对象的handler