Android bluetooth介绍（蓝牙扫描(scan)设备分析） _BlueTooth

幼敏悟过人，读书辄成诵。这篇文章主要讲述Android bluetooth介绍：蓝牙扫描(scan)设备分析相关的知识，希望能为你提供帮助。
关键词：蓝牙blueZ A2DP、SINK、sink_connect、sink_disconnect、sink_suspend、sink_resume、sink_is_connected、sink_get_properties、AUDIO、DBUS
版本号：基于android4.2之前版本号 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！！

參考站点：
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、蓝牙扫描经常使用的方法：
蓝牙扫描的能够通过两种途径实现：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

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Hcitool扫描逻辑例如以下所看到的：

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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

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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。

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二、Hcitool触发逻辑分析
1、hcitool这部分代码比較简单，实现函数
idh.code\\external\\bluetooth\\bluez\\tools\\hcitool.c代码大致流程例如以下：

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通过所带的參数，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仅仅是当中一项。
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, ………… };

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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，当中hci_send_frame后面会解说，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怎样取得的。例如以下图所看到的：

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入口点hci_rx_work前面已经具体分析过了，这里就不说了。它里面会依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，还有其他几种扫描方式，比方：HCI_EV_INQUIRY_RESULT，HCI_EV_EXTENDED_INQUIRY_RESULT等。处理逻辑都几乎相同的，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；比方前面调用的inquiry_cache_dump函数就能够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
总体流程例如以下所看到的：

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（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函数的对比表
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、相应Native函数的实现
这里面有个知识点DBUS，这个后面我们单独去解说
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"//事实上DBUS_ADAPTER_IFACE 也就是 org.bluez.Adapter static 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相应。

（三）、DBUS部分

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1、DBUS相应方法的实现，这里跟JNI部分比較相似，也是用了函数结构体相应关系。
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又相应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相应结构体btd_adapter_ops中相应函数，例如以下：上面部分就相应到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 = https://www.songbingjia.com/android/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函数的运行。在这里面设置了socket的filter特性，包含包类型，包含事件类型；

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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); } ……………… }

内核这部分就比較统一的数据，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。

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【Android bluetooth介绍（蓝牙扫描(scan)设备分析）】（五）、EVENT返回状态

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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))//假设是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); else adapter_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 change emit_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); //把信号相相应的參数压进去 dbus_message_iter_append_basic(& iter, DBUS_TYPE_STRING, & name); //申请一个首地址。把前面压入的參数传入这个首地址 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 = https://www.songbingjia.com/android/(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相应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我们或许会更明确其他功能的由来：

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

（2）、以下我们重点分析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")) {//開始扫描 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); } 这样就能够通过broadcast发送ACTION_DISCOVERY_STARTED广播，注冊的receiver来响应了。

8、ACTION_DISCOVERY_STARTED\\ACTION_DISCOVERY_FINISHED的receiver分析
从代码中我们能够看到这个action一共同拥有两个receiver，一个是静态注冊的BluetoothDiscoveryReceiver,一个是动态注冊是ScanningStateChangedHandler。
（1）、BluetoothDiscoveryReceiver：这个receiver是在settings中的Androidmanifest中静态注冊的。用途：主要用于获取扫描開始和终止的时间。
idh.code\\packages\\apps\\Settings\\AndroidManifest.xml

< receiver android:name=".bluetooth.BluetoothDiscoveryReceiver"> < intent-filter> < action android:name="android.bluetooth.adapter.action.DISCOVERY_STARTED" /> < action android:name="android.bluetooth.adapter.action.DISCOVERY_FINISHED" /> < category android:name="android.intent.category.DEFAULT" /> < /intent-filter> < /receiver>

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	已完毕蓝牙搜索
ACTION_DISCOVERY_STARTED	已经開始搜索蓝牙设备
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，開始扫描
Main log中显示的log为DISCOVERY_STARTED
D BluetoothDiscoveryReceiver: Received:android.bluetooth.adapter.action.DISCOVERY_STARTED
HCI log 中：

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idh.code\\packages\\apps\\Settings\\src\\com\\android\\settings\\bluetooth\\BluetoothDiscoveryReceiver.java这个文件里就一个函数。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。扫描開始和结束的时间。 LocalBluetoothPreferences.persistDiscoveringTimestamp(context); } } }

ScanningStateChangedHandler的注冊及用途，要用于開始扫描。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动态注冊的，例如以下：

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函数实现例如以下：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)、调用注冊的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）、调用注冊的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》、假设扫描结束； removeOutOfRangeDevices(); } updateProgressUi(started); // 《2》、UI显示小圆圈扫描； }

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

private void removeOutOfRangeDevices() { Collection< CachedBluetoothDevice> 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)；例如以下图所看到的：

文章图片

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，開始扫描，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，開始扫描。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. //假设開始新的扫描，清除旧的能见设备。迭代反序由于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) {//假设扫描開始就不显示； cachedDevice.setVisible(false); } else {//对扫描的结果作出推断。假设之前扫描过，这次没有扫描到，就移除列表。 if (cachedDevice.getBondState() == BluetoothDevice.BOND_NONE & & cachedDevice.isVisible() == false) { mCachedDevices.remove(cachedDevice); } } } }