Android(安卓)bluetooth介绍（三）：蓝牙扫描(scan)设备分析

关键词：蓝牙blueZ A2DP、SINK、sink_connect、sink_disconnect、sink_suspend、sink_resume、sink_is_connected、sink_get_properties、AUDIO、DBUS
版本：基于android4.2之前版本 bluez
内核：linux/linux3.08
系统：android/android4.1.3.4
作者：xubin341719(欢迎转载，请注明作者，请尊重版权谢谢)
欢迎指正错误，共同学习、共同进步！！
参考网站：
http://blog.csdn.net/u011960402/article/details/17216563
http://www.cnblogs.com/fityme/archive/2013/04/13/3019471.html socket相关
http://hi.baidu.com/wwwkljoel/item/a35e5745d14e02e6bcf45170 setsockopt

Android bluetooth介绍（一）：基本概念及硬件接口
Android bluetooth介绍（二）： android 蓝牙代码架构及其uart 到rfcomm流程
Android bluetooth介绍（三）：蓝牙扫描(scan)设备分析
Android bluetooth介绍（四）： a2dp connect流程分析

一、蓝牙扫描常用的方法：
蓝牙扫描的可以通过两种途径实现：命令行hciitool扫描；Android界面触发，通过JNI、DUBS下发命令。
1、 命令行hciitool扫描（这部分通过Linux命令操作，跟android没有关系）
通过bluez的tool发送扫描命令，如：hcitoool scan
adb shell 下#hcitool scan扫描结果

Hcitool扫描逻辑如下所示：

2、Android界面触发，通过JNI、DUBS下发命令：通过android界面点击搜索设备

应用扫描触发逻辑流程：自上而下三种颜色，分别代表应用部分、JNI部分、linux blueZ部分。
二、Hcitool触发逻辑分析
1、hcitool这部分代码比较简单，实现函数
idh.code\external\bluetooth\bluez\tools\hcitool.c代码大致流程如下：

通过所带的参数，找到cmd_scan,进入hci_inquriy。这个函数中创建一个BTPROTO_HCI的socket,通过ioctlHCINQUIRY向内核读取数据，保存返回信息。

2、内核层逻辑：
当然IOCTL只是其中一项。
idh.code\kernel\net\bluetooth\ hci_sock.c

static const struct proto_ops hci_sock_ops = {………….ioctl= hci_sock_ioctl,.poll= datagram_poll,.listen= sock_no_listen,…………};

它的流程就是构造查询命令，放入命令队列，调度队列来发送命令，其中hci_send_frame后面会讲解，这里关键是命令的发送和数据的收集是分开的，所以它在里面会放弃2s的调度，以此来等待数据的收集，收集的数据放在hdev->inq_cache里面，我们来看看这个数据是如何取得的，如下图所示：

入口点hci_rx_work前面已经详细分析过了，这里就不说了，它里面会根据不同的事件类型做不同的处理，通常情况下，扫描都是带信号强度的扫描，所以走的hci_inquiry_result_with_rssi_evt路线，还有其它几种扫描方式，比如：HCI_EV_INQUIRY_RESULT，HCI_EV_EXTENDED_INQUIRY_RESULT等，处理逻辑都差不多的，里面会hci_inquiry_cache_update来把结果放到hdev->discovery链表里面去，供后面的查询；比如前面调用的inquiry_cache_dump函数就可以从这个链表里面把数据取出来，然后copy到用户层；
三、Android界面触发，通过JNI、DUBS下发命令
整体流程如下所示：

（一）、应用部分：
1、 idh.code\packages\apps\Settings\src\com\android\settings\bluetooth\DeviceListPreferenceFragment.java

  @Override    public boolean onPreferenceTreeClick(PreferenceScreen preferenceScreen,        Preference preference) {     …………        mLocalAdapter.startScanning(true);        return true;      }

2、 idh.code\packages\apps\Settings\src\com\android\settings\bluetooth\LocalBluetoothAdapter.java

 private final BluetoothAdapter mAdapter; void startScanning(boolean force) {        // Only start if we're not already scanning        if (!mAdapter.isDiscovering()) {            if (!force) {                // Don't scan more than frequently than SCAN_EXPIRATION_MS,                // unless forced                if (mLastScan + SCAN_EXPIRATION_MS > System.currentTimeMillis()) {                    return;                }                // If we are playing music, don't scan unless forced.                A2dpProfile a2dp = mProfileManager.getA2dpProfile();                if (a2dp != null && a2dp.isA2dpPlaying()) {                    return;                }            }            if (mAdapter.startDiscovery()) {                mLastScan = System.currentTimeMillis();            }        }}

3、idh.code\frameworks\base\core\java\android\bluetooth\BluetoothAdapter.java

    public boolean startDiscovery() {        if (getState() != STATE_ON) return false;        try {            return mService.startDiscovery();        } catch (RemoteException e) {Log.e(TAG, "", e);}        return false;    }

4、JNI函数的调用idh.code\frameworks\base\core\java\android\server\BluetoothService.java

private native boolean startDiscoveryNative();//Native函数声明public class BluetoothService extends IBluetooth.Stub {    private static final String TAG = "BluetoothService";    private static final boolean DBG = true;…………public synchronized boolean startDiscovery() {mContext.enforceCallingOrSelfPermission(BLUETOOTH_ADMIN_PERM,        "Need BLUETOOTH_ADMIN permission");        if (!isEnabledInternal()) return false;        return startDiscoveryNative();}………………}

（二）、JNI部分：
1、android_server_BluetoothService.cpp中JNI函数的对照表
idh.code\frameworks\base\core\jni\android_server_BluetoothService.cpp

static JNINativeMethod sMethods[] = {     /* name, signature, funcPtr */   ………………    {"startDiscoveryNative", "()Z", (void*)startDiscoveryNative},{"stopDiscoveryNative", "()Z", (void *)stopDiscoveryNative}, …………}

2、对应Native函数的实现
这里面有个知识点DBUS，这个后面我们单独去讲解
idh.code\frameworks\base\core\jni\android_server_BluetoothService.cpp

#define BLUEZ_DBUS_BASE_IFC       "org.bluez"#define DBUS_ADAPTER_IFACE BLUEZ_DBUS_BASE_IFC ".Adapter"//其实DBUS_ADAPTER_IFACE 也就是 org.bluez.Adapterstatic jboolean startDiscoveryNative(JNIEnv *env, jobject object) {………………    /* Compose the command */    msg = dbus_message_new_method_call(BLUEZ_DBUS_BASE_IFC,                                       get_adapter_path(env, object),                                       DBUS_ADAPTER_IFACE, "StartDiscovery");…………}Native函数startDiscoveryNative和字符串StartDiscovery对应。

（三）、DBUS部分

1、DBUS对应方法的实现，这里跟JNI部分比较类似，也是用了函数结构体对应关系。
idh.code\external\bluetooth\bluez\src\adapter.c

#define ADAPTER_INTERFACE"org.bluez.Adapter"static GDBusMethodTable adapter_methods[] = {………………{ "ReleaseSession","","",release_session},{ "StartDiscovery","","",adapter_start_discovery },{ "StopDiscovery","","",adapter_stop_discovery,G_DBUS_METHOD_FLAG_ASYNC},………………}

字符StartDiscovery又对应C中的实现函数adapter_start_discovery。
2、adapter_start_discovery的实现
idh.code\external\bluetooth\bluez\src\adapter.c

static DBusMessage *adapter_start_discovery(DBusConnection *conn,DBusMessage *msg, void *data){…………err = start_discovery(adapter);if (err < 0 && err != -EINPROGRESS)return btd_error_failed(msg, strerror(-err));done:req = create_session(adapter, conn, msg, 0,session_owner_exit);adapter->disc_sessions = g_slist_append(adapter->disc_sessions, req);return dbus_message_new_method_return(msg);}

3、 start_discovery调用
idh.code\external\bluetooth\bluez\src\adapter.c

const struct btd_adapter_ops *adapter_ops = NULL;static int start_discovery(struct btd_adapter *adapter){…………pending_remote_name_cancel(adapter);return adapter_ops->start_discovery(adapter->dev_id);}

adapter_ops对应结构体btd_adapter_ops中对应函数，如下：上面部分就对应到btd_adapter_ops中的hci_ops结构体。
4、btd_adapter_ops中的hci_ops结构体
idh.code\external\bluetooth\bluez\plugins\hciops.c

static struct btd_adapter_ops hci_ops = {………….set_powered = hciops_set_powered,.set_discoverable = hciops_set_discoverable,.set_pairable = hciops_set_pairable,.set_limited_discoverable = hciops_set_limited_discoverable,.start_discovery = hciops_start_discovery,.stop_discovery = hciops_stop_discovery,……………….create_bonding = hciops_create_bonding,.cancel_bonding = hciops_cancel_bonding,.read_local_oob_data = hciops_read_local_oob_data,.add_remote_oob_data = hciops_add_remote_oob_data,.remove_remote_oob_data = hciops_remove_remote_oob_data,.set_link_timeout = hciops_set_link_timeout,.retry_authentication = hciops_retry_authentication,};

5、hciops_start_discovery函数的实现
idh.code\external\bluetooth\bluez\plugins\hciops.c

static int hciops_start_discovery(int index){int adapter_type = get_adapter_type(index);switch (adapter_type) {case BR_EDR_LE:return hciops_start_inquiry(index, LENGTH_BR_LE_INQ);case BR_EDR: //蓝牙芯片为2.1+EDR的return hciops_start_inquiry(index, LENGTH_BR_INQ);case LE_ONLY:return hciops_start_scanning(index, TIMEOUT_LE_SCAN);default:return -EINVAL;}}

6、hciops_start_inquiry
idh.code\external\bluetooth\bluez\plugins\hciops.c

static int hciops_start_inquiry(int index, uint8_t length){struct dev_info *dev = &devs[index];uint8_t lap[3] = { 0x33, 0x8b, 0x9e };inquiry_cp inq_cp;DBG("hci%d length %u", index, length);memset(&inq_cp, 0, sizeof(inq_cp));memcpy(&inq_cp.lap, lap, 3);inq_cp.length = length;inq_cp.num_rsp = 0x00;if (hci_send_cmd(dev->sk, OGF_LINK_CTL,OCF_INQUIRY, INQUIRY_CP_SIZE, &inq_cp) < 0)return -errno;return 0;}

7、idh.code\external\bluetooth\bluez\lib\hci.c

/* HCI functions that require open device * dd - Device descriptor returned by hci_open_dev. */dd = socket(AF_BLUETOOTH, SOCK_RAW, BTPROTO_HCI);int hci_send_cmd(int dd, uint16_t ogf, uint16_t ocf, uint8_t plen, void *param){………………if (plen) {iv[2].iov_base = param;iv[2].iov_len  = plen;ivn = 3;}while (writev(dd, iv, ivn) < 0) {//writev这里把数据写到socket里面。if (errno == EAGAIN || errno == EINTR)continue;return -1;}return 0;}

（四）、内核部分：
1、HCI FILTER的设置
HCIsocket的类型为BTPROTO_HCI。上层调用setsockopt的时候，触发了内核的hci_sock_setsockopt函数的执行，在这里面设置了socket的filter特性，包括包类型，包括事件类型；

当上层调用setsockopt(sock, SOL_HCI, HCI_FILTER,&flt, sizeof(flt))时，触发相应的内核路径。
idh.code\kernel\net\bluetooth\hci_sock.c

static const struct proto_ops hci_sock_ops = {.family= PF_BLUETOOTH,.owner= THIS_MODULE,………….shutdown= sock_no_shutdown,.setsockopt= hci_sock_setsockopt,.getsockopt= hci_sock_getsockopt,.connect= sock_no_connect,…………};

idh.code\kernel\net\bluetooth\hci_sock.c

static int hci_sock_setsockopt(struct socket *sock, int level, int optname, char __user *optval, unsigned int len){………………case HCI_FILTER:{struct hci_filter *f = &hci_pi(sk)->filter;uf.type_mask = f->type_mask;uf.opcode    = f->opcode;uf.event_mask[0] = *((u32 *) f->event_mask + 0);uf.event_mask[1] = *((u32 *) f->event_mask + 1);}………………}

内核这部分就比较统一的数据，通过hci_send_cmd把命令发出去，HCI_FILTER这个地方的处理还没理解，后面补充。
Writev函数通过socket把数据写下去，经过VFS层，调用到内核空间的sendmsg函数。

（五）、EVENT返回状态

Controller收到查询命令后，返回一个命令状态
1、cmd_status
idh.code\external\bluetooth\bluez\plugins\hciops.c

switch (eh->evt) {case EVT_CMD_STATUS:cmd_status(index, ptr);break;static inline void cmd_status(int index, void *ptr){evt_cmd_status *evt = ptr;uint16_t opcode = btohs(evt->opcode);if (opcode == cmd_opcode_pack(OGF_LINK_CTL, OCF_INQUIRY))//如果是inquriy做特殊处理；cs_inquiry_evt(index, evt->status);}

2、cs_inquiry_evt的实现 idh.code\external\bluetooth\bluez\plugins\hciops.c

static inline void cs_inquiry_evt(int index, uint8_t status){if (status) {//错误信息error("Inquiry Failed with status 0x%02x", status);return;}set_state(index, DISCOV_INQ);//设置状态为INQ，向上层回复discoverying的property change}

3、设置不同的DISCOV 状态 idh.code\external\bluetooth\bluez\plugins\hciops.c

static void set_state(int index, int state){………………switch (dev->discov_state) {case DISCOV_HALTED://停止发现;if (adapter_get_state(adapter) == STATE_SUSPENDED)return;if (is_resolvname_enabled() &&adapter_has_discov_sessions(adapter))adapter_set_state(adapter, STATE_RESOLVNAME);elseadapter_set_state(adapter, STATE_IDLE);break;case DISCOV_INQ:case DISCOV_SCAN://扫描发现；adapter_set_state(adapter, STATE_DISCOV);break;}}

4、设置adapter的状态 idh.code\external\bluetooth\bluez\src\adapter.c

idh.code\external\bluetooth\bluez\src\adapter.c#define ADAPTER_INTERFACE"org.bluez.Adapter"void adapter_set_state(struct btd_adapter *adapter, int state){…………case STATE_DISCOV:discov_active = TRUE;//向上层回复discovering的property changeemit_property_changed(connection, path,ADAPTER_INTERFACE, "Discovering",DBUS_TYPE_BOOLEAN, &discov_active);break;…………}

emit_property_changed发送PropertyChanged的消息，消息内容为Discovering。通知上层BluetoothEventLoop进行Discovering。
5、emit_property_changed发送Discovering消息的实现 idh.code\external\bluetooth\bluez\src\dbus-common.c
这部分涉及到DBUS内容

dbus_bool_t emit_property_changed(DBusConnection *conn,const char *path,const char *interface,const char *name,int type, void *value){DBusMessage *signal;DBusMessageIter iter;signal = dbus_message_new_signal(path, interface, "PropertyChanged"); // 创建消息对象并标识路径 if (!signal) {error("Unable to allocate new %s.PropertyChanged signal",interface);return FALSE;}dbus_message_iter_init_append(signal, &iter);//把信号相对应的参数压进去dbus_message_iter_append_basic(&iter, DBUS_TYPE_STRING, &name);//申请一个首地址，把前面压入的参数传入这个首地址append_variant(&iter, type, value);//return g_dbus_send_message(conn, signal);//启动发送调用，并释放发送相关消息信息}

6、DBUS消息接收的实现 idh.code\frameworks\base\core\jni\android_server_BluetoothEventLoop.cpp

// Called by dbus during WaitForAndDispatchEventNative()static DBusHandlerResult event_filter(DBusConnection *conn, DBusMessage *msg,                                      void *data) {…………else if (dbus_message_is_signal(msg, "org.bluez.Adapter", "PropertyChanged")) {        jobjectArray str_array = parse_adapter_property_change(env, msg);//（1）、对收到消息的解析        if (str_array != NULL) {            /* Check if bluetoothd has (re)started, if so update the path. */            jstring property =(jstring) env->GetObjectArrayElement(str_array, 0);            const char *c_property = env->GetStringUTFChars(property, NULL);            if (!strncmp(c_property, "Powered", strlen("Powered"))) {                jstring value =                    (jstring) env->GetObjectArrayElement(str_array, 1);                const char *c_value = env->GetStringUTFChars(value, NULL);                if (!strncmp(c_value, "true", strlen("true")))                    nat->adapter = get_adapter_path(nat->conn);                env->ReleaseStringUTFChars(value, c_value);            }            env->ReleaseStringUTFChars(property, c_property);            env->CallVoidMethod(nat->me,                              method_onPropertyChanged,//（2）、method_onPropertyChanged NATVIE函数的实现                              str_array);        } else LOG_AND_FREE_DBUS_ERROR_WITH_MSG(&err, msg);        goto success;}

（1）、对收到消息的解析 idh.code\frameworks\base\core\jni\android_bluetooth_common.cpp

jobjectArray parse_adapter_property_change(JNIEnv *env, DBusMessage *msg) {    return parse_property_change(env, msg, (Properties *) &adapter_properties,                    sizeof(adapter_properties) / sizeof(Properties));}

针对org.bluez.Adapter不同的消息类型
idh.code\frameworks\base\core\jni\android_bluetooth_common.cpp

static Properties adapter_properties[] = {    {"Address", DBUS_TYPE_STRING},    {"Name", DBUS_TYPE_STRING},    {"Class", DBUS_TYPE_UINT32},    {"Powered", DBUS_TYPE_BOOLEAN},    {"Discoverable", DBUS_TYPE_BOOLEAN},    {"DiscoverableTimeout", DBUS_TYPE_UINT32},    {"Pairable", DBUS_TYPE_BOOLEAN},    {"PairableTimeout", DBUS_TYPE_UINT32},    {"Discovering", DBUS_TYPE_BOOLEAN},    {"Devices", DBUS_TYPE_ARRAY},    {"UUIDs", DBUS_TYPE_ARRAY},};

（2）、method_onPropertyChanged NATVIE函数的实现 idh.code\frameworks\base\core\jni\android_server_BluetoothEventLoop.cpp

static void classInitNative(JNIEnv* env, jclass clazz) {    ALOGV("%s", __FUNCTION__);#ifdef HAVE_BLUETOOTH    method_onPropertyChanged = env->GetMethodID(clazz, "onPropertyChanged",                                                "([Ljava/lang/String;)V");method_onDevicePropertyChanged = env->GetMethodID(clazz, "onDevicePropertyChanged","(Ljava/lang/String;[Ljava/lang/String;)V");…………}

7、JNI调用onPropertyChanged对应JAVA的实现，在BluetoothEventLoop.java
idh.code\frameworks\base\core\java\android\server\BluetoothEventLoop.java中

   private static native void classInitNative();/*package*/ void onPropertyChanged(String[] propValues) { ………………        log("Property Changed: " + propValues[0] + " : " + propValues[1]);        String name = propValues[0];        if (name.equals("Name")) {//获取蓝牙名字；   …………        } else if (name.equals("Pairable") || name.equals("Discoverable")) {//配对；           ………………        } else if (name.equals("Discovering")) {//扫描查询；            Intent intent;            adapterProperties.setProperty(name, propValues[1]);            if (propValues[1].equals("true")) {                intent = new Intent(BluetoothAdapter.ACTION_DISCOVERY_STARTED);            } else {                // Stop the discovery.                mBluetoothService.cancelDiscovery();                intent = new Intent(BluetoothAdapter.ACTION_DISCOVERY_FINISHED);            }            mContext.sendBroadcast(intent, BLUETOOTH_PERM);        } else if (name.equals("Devices") || name.equals("UUIDs")) {//Devices、UUID的获取；     ………………        } else if (name.equals("Powered")) {//蓝牙打开、关闭；            mBluetoothState.sendMessage(BluetoothAdapterStateMachine.POWER_STATE_CHANGED,                propValues[1].equals("true") ? new Boolean(true) : new Boolean(false));        } else if (name.equals("DiscoverableTimeout")) {            adapterProperties.setProperty(name, propValues[1]);        }    }

（1）、看到这份log我们也许会更明白其他功能的由来：

D BluetoothEventLoop: Property Changed: Powered : trueD BluetoothEventLoop: Property Changed: Pairable : trueD BluetoothEventLoop: Property Changed: Class : 5898764D BluetoothEventLoop: Property Changed: Pairable : trueD BluetoothEventLoop: Property Changed: Discoverable : falseD BluetoothEventLoop: Property Changed: Discovering : trueD BluetoothEventLoop: Property Changed: Discovering : falseD BluetoothEventLoop: Property Changed: Devices : 1D BluetoothEventLoop: Device property changed: 94:20:53:01:15:90 property: Connected value: trueD BluetoothEventLoop: Device property changed: 94:20:53:01:15:90 property: Paired value: trueD BluetoothEventLoop: Device property changed: 94:20:53:01:15:90 property: UUIDs value: 4

（2）、下面我们重点分析Discovering这部分：
idh.code\frameworks\base\core\java\android\server\BluetoothEventLoop.java

else if (name.equals("Discovering")) {            Intent intent;            adapterProperties.setProperty(name, propValues[1]);            if (propValues[1].equals("true")) {//开始扫描                intent = new Intent(BluetoothAdapter.ACTION_DISCOVERY_STARTED);//            } else {                // Stop the discovery. //停止扫描                mBluetoothService.cancelDiscovery();                intent = new Intent(BluetoothAdapter.ACTION_DISCOVERY_FINISHED);            }            mContext.sendBroadcast(intent, BLUETOOTH_PERM);        }这样就可以通过broadcast发送ACTION_DISCOVERY_STARTED广播，注册的receiver来响应了。

8、ACTION_DISCOVERY_STARTED\ACTION_DISCOVERY_FINISHED的receiver分析
从代码中我们可以看到这个action一共有两个receiver，一个是静态注册的BluetoothDiscoveryReceiver,一个是动态注册是ScanningStateChangedHandler。
（1）、BluetoothDiscoveryReceiver：这个receiver是在settings中的Androidmanifest中静态注册的。用途：主要用于获取扫描开始和终止的时间。
idh.code\packages\apps\Settings\AndroidManifest.xml

1）、ACTION_DISCOVERY_STARTED、ACTION_DISCOVERY_FINISHED和AndroidManifest.xml文件的联系
idh.code\frameworks\base\core\java\android\bluetooth\BluetoothAdapter.java

public final class BluetoothAdapter {    private static final String TAG = "BluetoothAdapter";private static final boolean DBG = false;…………    public static final String ACTION_DISCOVERY_STARTED =            "android.bluetooth.adapter.action.DISCOVERY_STARTED";    public static final String ACTION_DISCOVERY_FINISHED =            "android.bluetooth.adapter.action.DISCOVERY_FINISHED";…………}

2）、BluetoothAdapter，蓝牙适配器，直到我们建立bluetoothSocket连接之前，都要不断操作它。
BluetoothAdapter中的动作常量

ACTION_DISCOVERY_FINISHED	已完成蓝牙搜索
ACTION_DISCOVERY_STARTED	已经开始搜索蓝牙设备
ACTION_LOCAL_NAME_CHANGED	更改蓝牙的名字
ACTION_REQUEST_DISCOVERABLE	请求能够被搜索
ACTION_REQUEST_ENABLE	请求启动蓝牙
ACTION_SCAN_MODE_CHANGED	扫描模式已经改变
ACTION_STATE_CHANGED	状态已改变
ACTION_CONNECTION_STATE_CHANGED

3）、收到广播后函数实现，开始扫描
Main log中显示的log为DISCOVERY_STARTED
D BluetoothDiscoveryReceiver: Received:android.bluetooth.adapter.action.DISCOVERY_STARTED
HCI log 中：

idh.code\packages\apps\Settings\src\com\android\settings\bluetooth\BluetoothDiscoveryReceiver.java这个文件中就一个函数，还是比简单

public final class BluetoothDiscoveryReceiver extends BroadcastReceiver {    private static final String TAG = "BluetoothDiscoveryReceiver";    private static final boolean DEBUG = Debug.isDebug();    @Override    public void onReceive(Context context, Intent intent) {        String action = intent.getAction();        if (DEBUG) Log.d(TAG, "Received: " + action);        if (action.equals(BluetoothAdapter.ACTION_DISCOVERY_STARTED) ||                action.equals(BluetoothAdapter.ACTION_DISCOVERY_FINISHED)) {    //共享时间戳，扫描开始和结束的时间。    LocalBluetoothPreferences.persistDiscoveringTimestamp(context);        }    }}

ScanningStateChangedHandler的注册及用途，要用于开始扫描，和扫描显示界面的控制。
这个receiver是在idh.code\packages\apps\Settings\src\com\android\settings\bluetooth\BluetoothEventManager.java动态注册的，如下：

BluetoothEventManager(LocalBluetoothAdapter adapter,            CachedBluetoothDeviceManager deviceManager, Context context) {mLocalAdapter = adapter;…………// Bluetooth on/off broadcasts addHandler(BluetoothAdapter.ACTION_STATE_CHANGED, new AdapterStateChangedHandler());// Discovery broadcastsaddHandler(BluetoothAdapter.ACTION_DISCOVERY_STARTED, new ScanningStateChangedHandler(true));        addHandler(BluetoothAdapter.ACTION_DISCOVERY_FINISHED, new ScanningStateChangedHandler(false));…………}

（1）、ScanningStateChangedHandler函数实现如下：idh.code\packages\apps\Settings\src\com\android\settings\bluetooth\BluetoothEventManager.java

 private class ScanningStateChangedHandler implements Handler {        private final boolean mStarted;        ScanningStateChangedHandler(boolean started) {            mStarted = started;        }        public void onReceive(Context context, Intent intent,                BluetoothDevice device) {            synchronized (mCallbacks) {//1)、调用注册的callback中的onScanningStateChanged函数。                for (BluetoothCallback callback : mCallbacks) {                    callback.onScanningStateChanged(mStarted);                }            }//2）、这个函数就是把上次扫描到设备、和之前的设备做相应处理；            mDeviceManager.onScanningStateChanged(mStarted);            LocalBluetoothPreferences.persistDiscoveringTimestamp(context);        }}

1）、调用注册的callback中的callback.onScanningStateChanged(mStarted)函数。
idh.code\packages\apps\Settings\src\com\android\settings\bluetooth\DeviceListPreferenceFragment.java

    public void onScanningStateChanged(boolean started) {        if (started == false) {//《1》、如果扫描结束；            removeOutOfRangeDevices();        }        updateProgressUi(started);// 《2》、UI显示小圆圈扫描；}

《1》、如果扫描结束；removeOutOfRangeDevices();
idh.code\packages\apps\Settings\src\com\android\settings\bluetooth\DeviceListPreferenceFragment.java

private void removeOutOfRangeDevices() {    Collection cachedDevices =            mLocalManager.getCachedDeviceManager().getCachedDevicesCopy();    for (CachedBluetoothDevice cachedDevice : cachedDevices) {         if (cachedDevice.getBondState() == BluetoothDevice.BOND_NONE &&             cachedDevice.isVisible() == false) {             BluetoothDevicePreference preference = mDevicePreferenceMap.get(cachedDevice);             if (preference != null) {                 mDeviceListGroup.removePreference(preference);             }             mDevicePreferenceMap.remove(cachedDevice);          }     }}

《2》、UI显示小圆圈扫描，updateProgressUi(started)；如下图所示：

idh.code\packages\apps\Settings\src\com\android\settings\bluetooth\DeviceListPreferenceFragment.java

private void updateProgressUi(boolean start) {    if (mDeviceListGroup instanceof ProgressCategory) {        ((ProgressCategory) mDeviceListGroup).setProgress(start);    }}

2）、这部分的作用，开始扫描，不显示列表中内容，或把之前列表中没扫描到的设备清除
mDeviceManager.onScanningStateChanged(mStarted);
idh.code\packages\apps\Settings\src\com\android\settings\bluetooth\CachedBluetoothDevice.java

private void updateProgressUi(boolean start) {    if (mDeviceListGroup instanceof ProgressCategory) {        ((ProgressCategory) mDeviceListGroup).setProgress(start);    }}2）、这部分的作用，开始扫描，不显示列表中内容，或把之前列表中没扫描到的设备清除mDeviceManager.onScanningStateChanged(mStarted);idh.code\packages\apps\Settings\src\com\android\settings\bluetooth\ CachedBluetoothDevice.java    public synchronized void onScanningStateChanged(boolean started) {        // If starting a new scan, clear old visibility        // Iterate in reverse order since devices may be removed.        //如果开始新的扫描，清除旧的能见设备，迭代反序因为有的设备可能被删除        for (int i = mCachedDevices.size() - 1; i >= 0; i--) {            CachedBluetoothDevice cachedDevice = mCachedDevices.get(i);            if (started) {//如果扫描开始就不显示；                cachedDevice.setVisible(false);            } else {//对扫描的结果作出判断，如果之前扫描过，这次没有扫描到，就移除列表。                if (cachedDevice.getBondState() == BluetoothDevice.BOND_NONE &&                        cachedDevice.isVisible() == false) {                    mCachedDevices.remove(cachedDevice);                }            }        }    }

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