安卓蓝牙扫描流程

目录

系统广播

流程图

源码跟踪

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系统广播

扫描开启广播：BluetoothAdapter.ACTION_DISCOVERY_STARTED = "android.bluetooth.adapter.action.DISCOVERY_STARTED";扫描关闭广播：BluetoothAdapter.ACTION_DISCOVERY_FINISHED = "android.bluetooth.adapter.action.DISCOVERY_FINISHED";扫描结果广播：BluetoothAdapter.ACTION_FOUND = "android.bluetooth.device.action.FOUND";

流程图

安卓系统中应用Application通过蓝牙适配器接口BluetoothAdapter.startDiscovery()的调用触发搜索流程的开始，从这里开始流程分析。

源码跟踪

frameworks\base\core\java\android\bluetooth\BluetoothAdapter.java中调用 startDiscovery

    public boolean startDiscovery() {if (getState() != STATE_ON) {return false;}try {mServiceLock.readLock().lock();if (mService != null) {return mService.startDiscovery(getOpPackageName(), getAttributionTag());}} catch (RemoteException e) {Log.e(TAG, "", e);} finally {mServiceLock.readLock().unlock();}return false;}

这里的Service.startDiscovery属于aidl跨进程通信，通过IBluetooth.aidl调用远程服务中packages\apps\Bluetooth\src\com\android\bluetooth\btservice\AdapterService.java中的startDiscovery

    boolean startDiscovery(String callingPackage, @Nullable String callingFeatureId) {UserHandle callingUser = UserHandle.of(UserHandle.getCallingUserId());debugLog("startDiscovery");mAppOps.checkPackage(Binder.getCallingUid(), callingPackage);boolean isQApp = Utils.isQApp(this, callingPackage);String permission = null;if (Utils.checkCallerHasNetworkSettingsPermission(this)) {permission = android.Manifest.permission.NETWORK_SETTINGS;} else if (Utils.checkCallerHasNetworkSetupWizardPermission(this)) {permission = android.Manifest.permission.NETWORK_SETUP_WIZARD;} else if (isQApp) {if (!Utils.checkCallerHasFineLocation(this, mAppOps, callingPackage, callingFeatureId,callingUser)) {return false;}permission = android.Manifest.permission.ACCESS_FINE_LOCATION;} else {if (!Utils.checkCallerHasCoarseLocation(this, mAppOps, callingPackage, callingFeatureId,callingUser)) {return false;}permission = android.Manifest.permission.ACCESS_COARSE_LOCATION;}synchronized (mDiscoveringPackages) {mDiscoveringPackages.add(new DiscoveringPackage(callingPackage, permission));}return startDiscoveryNative();}

调用packages\apps\Bluetooth\jni\com_android_bluetooth_btservice_AdapterService.cpp中的startDiscoveryNative

static jboolean startDiscoveryNative(JNIEnv* env, jobject obj) {ALOGV("%s", __func__);if (!sBluetoothInterface) return JNI_FALSE;int ret = sBluetoothInterface->start_discovery();return (ret == BT_STATUS_SUCCESS) ? JNI_TRUE : JNI_FALSE;
}

调到system\bt\btif\src\bluetooth.cc中的start_discovery

static int start_discovery(void) {/* sanity check */完整性检查if (!interface_ready()) return BT_STATUS_NOT_READY;return btif_dm_start_discovery();
}

start_discovery调到system\bt\btif\src\btif_dm.cc中的btif_dm_start_discovery；btif_dm.cc用于设备管理相关功能

/********************************************************************************* Function         btif_dm_start_discovery** Description      Start device discovery/inquiry** Returns          bt_status_t*******************************************************************************/
bt_status_t btif_dm_start_discovery(void) {tBTA_DM_INQ inq_params;tBTA_SERVICE_MASK services = 0;BTIF_TRACE_EVENT("%s", __func__);/* Cleanup anything remaining on index 0 */do_in_main_thread(FROM_HERE,base::Bind(&BTM_BleAdvFilterParamSetup, BTM_BLE_SCAN_COND_DELETE, 0,nullptr, base::Bind(&bte_scan_filt_param_cfg_evt, 0)));auto adv_filt_param = std::make_unique<btgatt_filt_param_setup_t>();/* Add an allow-all filter on index 0*/adv_filt_param->dely_mode = IMMEDIATE_DELY_MODE;adv_filt_param->feat_seln = ALLOW_ALL_FILTER;adv_filt_param->filt_logic_type = BTA_DM_BLE_PF_FILT_LOGIC_OR;adv_filt_param->list_logic_type = BTA_DM_BLE_PF_LIST_LOGIC_OR;adv_filt_param->rssi_low_thres = LOWEST_RSSI_VALUE;adv_filt_param->rssi_high_thres = LOWEST_RSSI_VALUE;do_in_main_thread(FROM_HERE, base::Bind(&BTM_BleAdvFilterParamSetup, BTM_BLE_SCAN_COND_ADD,0, base::Passed(&adv_filt_param),base::Bind(&bte_scan_filt_param_cfg_evt, 0)));/* TODO: Do we need to handle multiple inquiries at the same time? *//* Set inquiry params and call API */inq_params.mode = BTA_DM_GENERAL_INQUIRY | BTA_BLE_GENERAL_INQUIRY;inq_params.duration = BTIF_DM_DEFAULT_INQ_MAX_DURATION;inq_params.max_resps = BTIF_DM_DEFAULT_INQ_MAX_RESULTS;inq_params.report_dup = true;inq_params.filter_type = BTA_DM_INQ_CLR;/* TODO: Filter device by BDA needs to be implemented here *//* Will be enabled to true once inquiry busy level has been received */btif_dm_inquiry_in_progress = false;/* find nearby devices */BTA_DmSearch(&inq_params, services, bte_search_devices_evt);return BT_STATUS_SUCCESS;
}

再调到system\bt\bta\dm\bta_dm_api.cc中的BTA_DmSearch

/********************************************************************************* Function         BTA_DmSearch** Description      This function searches for peer Bluetooth devices. It*                  performs an inquiry and gets the remote name for devices.*                  Service discovery is done if services is non zero*** Returns          void*******************************************************************************/
void BTA_DmSearch(tBTA_DM_INQ* p_dm_inq, tBTA_SERVICE_MASK services,tBTA_DM_SEARCH_CBACK* p_cback) {tBTA_DM_API_SEARCH* p_msg =(tBTA_DM_API_SEARCH*)osi_calloc(sizeof(tBTA_DM_API_SEARCH));p_msg->hdr.event = BTA_DM_API_SEARCH_EVT;memcpy(&p_msg->inq_params, p_dm_inq, sizeof(tBTA_DM_INQ));p_msg->services = services;p_msg->p_cback = p_cback;p_msg->rs_res = BTA_DM_RS_NONE;bta_sys_sendmsg(p_msg);//发送到另一个线程
}

调用bta_sys_sendmsg向BTA发送扫描任务消息。bta_sys_sendmsg是蓝牙协议栈的进程间收发消息机制，比较复杂。通过搜索event标记BTA_DM_API_SEARCH_EVT可以找到system\bt\bta\dm\bta_dm_act.cc中bta_dm_rs_cback

/********************************************************************************* Function         bta_dm_rs_cback** Description      Receives the role switch complete event** Returns*******************************************************************************/
static void bta_dm_rs_cback(UNUSED_ATTR void* p1) {APPL_TRACE_WARNING("bta_dm_rs_cback:%d", bta_dm_cb.rs_event);if (bta_dm_cb.rs_event == BTA_DM_API_SEARCH_EVT) {bta_dm_cb.search_msg.rs_res =BTA_DM_RS_OK; /* do not care about the result for now */bta_dm_cb.rs_event = 0;bta_dm_search_start((tBTA_DM_MSG*)&bta_dm_cb.search_msg);//调用内部的开启扫描方法}
}

这里判断如果event是BTA_DM_API_SEARCH_EVT就调用bta本身的bta_dm_search_start方法

/********************************************************************************* Function         bta_dm_search_start** Description      Starts an inquiry*** Returns          void*******************************************************************************/
void bta_dm_search_start(tBTA_DM_MSG* p_data) {tBTM_INQUIRY_CMPL result = {};size_t len = sizeof(Uuid) * p_data->search.num_uuid;bta_dm_gattc_register();APPL_TRACE_DEBUG("%s avoid_scatter=%d", __func__,p_bta_dm_cfg->avoid_scatter);if (p_bta_dm_cfg->avoid_scatter &&(p_data->search.rs_res == BTA_DM_RS_NONE) &&bta_dm_check_av(BTA_DM_API_SEARCH_EVT)) {LOG(INFO) << __func__ << ": delay search to avoid scatter";memcpy(&bta_dm_cb.search_msg, &p_data->search, sizeof(tBTA_DM_API_SEARCH));return;}BTM_ClearInqDb(nullptr); //清楚BTM中之前保存的搜索数据/* save search params */bta_dm_search_cb.p_search_cback = p_data->search.p_cback;bta_dm_search_cb.services = p_data->search.services;osi_free_and_reset((void**)&bta_dm_search_cb.p_srvc_uuid);if ((bta_dm_search_cb.num_uuid = p_data->search.num_uuid) != 0 &&p_data->search.p_uuid != nullptr) {bta_dm_search_cb.p_srvc_uuid = (Uuid*)osi_malloc(len);*bta_dm_search_cb.p_srvc_uuid = *p_data->search.p_uuid;}result.status = BTM_StartInquiry((tBTM_INQ_PARMS*)&p_data->search.inq_params,bta_dm_inq_results_cb, bta_dm_inq_cmpl_cb);//调用btm中的启动扫描APPL_TRACE_EVENT("%s status=%d", __func__, result.status);if (result.status != BTM_CMD_STARTED) {LOG(ERROR) << __func__ << ": BTM_StartInquiry returned "<< std::to_string(result.status);result.num_resp = 0;bta_dm_inq_cmpl_cb((void*)&result);}
}

这里主要就是先清楚BTM中之前的搜索数据，然后保存搜索的参数，调用btm中BTM_StartInquiry方法进行扫描。btm中的扫描在system\bt\stack\btm\btm_inq.cc里

/********************************************************************************* Function         BTM_StartInquiry** Description      This function is called to start an inquiry.** Parameters:      p_inqparms - pointer to the inquiry information*                      mode - GENERAL or LIMITED inquiry, BR/LE bit mask*                             seperately*                      duration - length in 1.28 sec intervals (If '0', the*                                 inquiry is CANCELLED)*                      max_resps - maximum amount of devices to search for*                                  before ending the inquiry*                      filter_cond_type - BTM_CLR_INQUIRY_FILTER,*                                         BTM_FILTER_COND_DEVICE_CLASS, or*                                         BTM_FILTER_COND_BD_ADDR*                      filter_cond - value for the filter (based on*                                                          filter_cond_type)**                  p_results_cb   - Pointer to the callback routine which gets*                                called upon receipt of an inquiry result. If*                                this field is NULL, the application is not*                                notified.**                  p_cmpl_cb   - Pointer to the callback routine which gets*                                called upon completion.  If this field is*                                NULL, the application is not notified when*                                completed.* Returns          tBTM_STATUS*                  BTM_CMD_STARTED if successfully initiated*                  BTM_BUSY if already in progress*                  BTM_ILLEGAL_VALUE if parameter(s) are out of range*                  BTM_NO_RESOURCES if could not allocate resources to start*                                   the command*                  BTM_WRONG_MODE if the device is not up.*******************************************************************************/
tBTM_STATUS BTM_StartInquiry(tBTM_INQ_PARMS* p_inqparms,tBTM_INQ_RESULTS_CB* p_results_cb,tBTM_CMPL_CB* p_cmpl_cb) {tBTM_INQUIRY_VAR_ST* p_inq = &btm_cb.btm_inq_vars;if (bluetooth::shim::is_gd_shim_enabled()) {return bluetooth::shim::BTM_StartInquiry(p_inqparms, p_results_cb,p_cmpl_cb);}BTM_TRACE_API("BTM_StartInquiry: mode: %d, dur: %d, rsps: %d, flt: %d",p_inqparms->mode, p_inqparms->duration, p_inqparms->max_resps,p_inqparms->filter_cond_type);/* Only one active inquiry is allowed in this implementation.Also do not allow an inquiry if the inquiry filter is being updated */if (p_inq->inq_active || p_inq->inqfilt_active) {LOG(ERROR) << __func__ << ": BTM_BUSY";return (BTM_BUSY);} else {p_inq->scan_type = INQ_GENERAL;}/*** Make sure the device is ready ***/if (!BTM_IsDeviceUp()) {LOG(ERROR) << __func__ << ": adapter is not up";return BTM_WRONG_MODE;}if ((p_inqparms->mode & BTM_BR_INQUIRY_MASK) != BTM_GENERAL_INQUIRY &&(p_inqparms->mode & BTM_BR_INQUIRY_MASK) != BTM_LIMITED_INQUIRY &&(p_inqparms->mode & BTM_BLE_INQUIRY_MASK) != BTM_BLE_GENERAL_INQUIRY &&(p_inqparms->mode & BTM_BLE_INQUIRY_MASK) != BTM_BLE_LIMITED_INQUIRY) {LOG(ERROR) << __func__ << ": illegal inquiry mode "<< std::to_string(p_inqparms->mode);return (BTM_ILLEGAL_VALUE);}/* Save the inquiry parameters to be used upon the completion of* setting/clearing the inquiry filter */p_inq->inqparms = *p_inqparms;/* Initialize the inquiry variables */p_inq->state = BTM_INQ_ACTIVE_STATE;p_inq->p_inq_cmpl_cb = p_cmpl_cb;p_inq->p_inq_results_cb = p_results_cb;p_inq->inq_cmpl_info.num_resp = 0; /* Clear the results counter */p_inq->inq_active = p_inqparms->mode;BTM_TRACE_DEBUG("BTM_StartInquiry: p_inq->inq_active = 0x%02x",p_inq->inq_active);tBTM_STATUS status = BTM_CMD_STARTED;/* start LE inquiry here if requested */if ((p_inqparms->mode & BTM_BLE_INQUIRY_MASK)) {if (!controller_get_interface()->supports_ble()) {LOG(ERROR) << __func__ << ": trying to do LE scan on a non-LE adapter";p_inq->inqparms.mode &= ~BTM_BLE_INQUIRY_MASK;status = BTM_ILLEGAL_VALUE;} else {/* BLE for now does not support filter condition for inquiry */status = btm_ble_start_inquiry((uint8_t)(p_inqparms->mode & BTM_BLE_INQUIRY_MASK),p_inqparms->duration);if (status != BTM_CMD_STARTED) {LOG(ERROR) << __func__ << ": Error Starting LE Inquiry";p_inq->inqparms.mode &= ~BTM_BLE_INQUIRY_MASK;}}p_inqparms->mode &= ~BTM_BLE_INQUIRY_MASK;BTM_TRACE_DEBUG("BTM_StartInquiry: mode = %02x", p_inqparms->mode);}/* we're done with this routine if BR/EDR inquiry is not desired. */if ((p_inqparms->mode & BTM_BR_INQUIRY_MASK) == BTM_INQUIRY_NONE) {return status;}/* BR/EDR inquiry portion *//* If a filter is specified, then save it for later and clear the currentfilter.The setting of the filter is done upon completion of clearing of thepreviousfilter.*/switch (p_inqparms->filter_cond_type) {case BTM_CLR_INQUIRY_FILTER:p_inq->state = BTM_INQ_SET_FILT_STATE;break;case BTM_FILTER_COND_DEVICE_CLASS:case BTM_FILTER_COND_BD_ADDR:/* The filter is not being used so simply clear it;the inquiry can start after this operation */p_inq->state = BTM_INQ_CLR_FILT_STATE;p_inqparms->filter_cond_type = BTM_CLR_INQUIRY_FILTER;/* =============>>>> adding LE filtering here ????? */break;default:LOG(ERROR) << __func__ << ": invalid filter condition type "<< std::to_string(p_inqparms->filter_cond_type);return (BTM_ILLEGAL_VALUE);}/* Before beginning the inquiry the current filter must be cleared, so* initiate the command */status = btm_set_inq_event_filter(p_inqparms->filter_cond_type,&p_inqparms->filter_cond);if (status != BTM_CMD_STARTED) {LOG(ERROR) << __func__ << ": failed to set inquiry event filter";p_inq->state = BTM_INQ_INACTIVE_STATE;}return (status);
}

调用system\bt\stack\btm\btm_ble_gap.cc 中的btm_ble_start_inquiry

/********************************************************************************* Function         btm_ble_start_inquiry** Description      This function is called to start BLE inquiry procedure.*                  If the duration is zero, the periodic inquiry mode is*                  cancelled.** Parameters:      mode - GENERAL or LIMITED inquiry*                  p_inq_params - pointer to the BLE inquiry parameter.*                  p_results_cb - callback returning pointer to results*                                 (tBTM_INQ_RESULTS)*                  p_cmpl_cb - callback indicating the end of an inquiry**** Returns          BTM_CMD_STARTED if successfully started*                  BTM_NO_RESOURCES if could not allocate a message buffer*                  BTM_BUSY - if an inquiry is already active*******************************************************************************/
tBTM_STATUS btm_ble_start_inquiry(uint8_t mode, uint8_t duration) {tBTM_STATUS status = BTM_CMD_STARTED;tBTM_BLE_CB* p_ble_cb = &btm_cb.ble_ctr_cb;tBTM_INQUIRY_VAR_ST* p_inq = &btm_cb.btm_inq_vars;BTM_TRACE_DEBUG("btm_ble_start_inquiry: mode = %02x inq_active = 0x%02x",mode, btm_cb.btm_inq_vars.inq_active);/* if selective connection is active, or inquiry is already active, reject it*/if (BTM_BLE_IS_INQ_ACTIVE(p_ble_cb->scan_activity)) {BTM_TRACE_ERROR("LE Inquiry is active, can not start inquiry");return (BTM_BUSY);}if (!BTM_BLE_IS_SCAN_ACTIVE(p_ble_cb->scan_activity)) {btm_send_hci_set_scan_params(BTM_BLE_SCAN_MODE_ACTI, BTM_BLE_LOW_LATENCY_SCAN_INT,BTM_BLE_LOW_LATENCY_SCAN_WIN,btm_cb.ble_ctr_cb.addr_mgnt_cb.own_addr_type, SP_ADV_ALL);
#if (BLE_PRIVACY_SPT == TRUE)/* enable IRK list */btm_ble_enable_resolving_list_for_platform(BTM_BLE_RL_SCAN);
#endifp_ble_cb->inq_var.scan_type = BTM_BLE_SCAN_MODE_ACTI;p_ble_cb->inq_var.scan_duplicate_filter = BTM_BLE_DUPLICATE_DISABLE;status = btm_ble_start_scan();} else if ((p_ble_cb->inq_var.scan_interval !=BTM_BLE_LOW_LATENCY_SCAN_INT) ||(p_ble_cb->inq_var.scan_window != BTM_BLE_LOW_LATENCY_SCAN_WIN)) {BTM_TRACE_DEBUG("%s, restart LE scan with low latency scan params",__func__);btm_send_hci_scan_enable(BTM_BLE_SCAN_DISABLE, BTM_BLE_DUPLICATE_ENABLE);btm_send_hci_set_scan_params(BTM_BLE_SCAN_MODE_ACTI, BTM_BLE_LOW_LATENCY_SCAN_INT,BTM_BLE_LOW_LATENCY_SCAN_WIN,btm_cb.ble_ctr_cb.addr_mgnt_cb.own_addr_type, SP_ADV_ALL);btm_send_hci_scan_enable(BTM_BLE_SCAN_ENABLE, BTM_BLE_DUPLICATE_DISABLE);}if (status == BTM_CMD_STARTED) {p_inq->inq_active |= mode;p_ble_cb->scan_activity |= mode;BTM_TRACE_DEBUG("btm_ble_start_inquiry inq_active = 0x%02x",p_inq->inq_active);if (duration != 0) {/* start inquiry timer */uint64_t duration_ms = duration * 1000;alarm_set_on_mloop(p_ble_cb->inq_var.inquiry_timer, duration_ms,btm_ble_inquiry_timer_timeout, NULL);}}return status;
}

再调用btm_send_hci_scan_enable向HCI发送扫描通知

void btm_send_hci_scan_enable(uint8_t enable, uint8_t filter_duplicates) {if (controller_get_interface()->supports_ble_extended_advertising()) {btsnd_hcic_ble_set_extended_scan_enable(enable, filter_duplicates, 0x0000,0x0000);} else {btsnd_hcic_ble_set_scan_enable(enable, filter_duplicates);//真正与HCI打交道}
}

这里判断是否支持ble扩展，则调用system\bt\stack\hcic\hciblecmds.cc中的btsnd_hcic_ble_set_scan_enable

void btsnd_hcic_ble_set_scan_enable(uint8_t scan_enable, uint8_t duplicate) {BT_HDR* p = (BT_HDR*)osi_malloc(HCI_CMD_BUF_SIZE);uint8_t* pp = (uint8_t*)(p + 1);p->len = HCIC_PREAMBLE_SIZE + HCIC_PARAM_SIZE_BLE_WRITE_SCAN_ENABLE;p->offset = 0;UINT16_TO_STREAM(pp, HCI_BLE_WRITE_SCAN_ENABLE);UINT8_TO_STREAM(pp, HCIC_PARAM_SIZE_BLE_WRITE_SCAN_ENABLE);UINT8_TO_STREAM(pp, scan_enable);UINT8_TO_STREAM(pp, duplicate);btu_hcif_send_cmd(LOCAL_BR_EDR_CONTROLLER_ID, p);//这里向hci层发命令
}

这里通过和HCI层的通信，host告诉controlor蓝牙地址、数据、命令等，从而控制底层硬件发起配对操作。btu如何与hci通信也比较复杂...

扫描结果返回

主要看下扫描到的设备信息返回。开始扫描和结束扫描的流程见图

之前在调用了system\bt\bta\dm\bta_dm_act.cc中bta_dm_search_start时，传了三个参数，第一个是启动扫描所需传下去的参数，第二个bta_dm_inq_results_cb是扫描结果返回的回调，第三个是扫描完成的回调。

  result.status = BTM_StartInquiry((tBTM_INQ_PARMS*)&p_data->search.inq_params,bta_dm_inq_results_cb, bta_dm_inq_cmpl_cb);//调用btm中的启动扫描

static void bta_dm_inq_results_cb(tBTM_INQ_RESULTS* p_inq, uint8_t* p_eir,uint16_t eir_len) {tBTA_DM_SEARCH result;tBTM_INQ_INFO* p_inq_info;uint16_t service_class;result.inq_res.bd_addr = p_inq->remote_bd_addr;memcpy(result.inq_res.dev_class, p_inq->dev_class, DEV_CLASS_LEN);BTM_COD_SERVICE_CLASS(service_class, p_inq->dev_class);result.inq_res.is_limited =(service_class & BTM_COD_SERVICE_LMTD_DISCOVER) ? true : false;result.inq_res.rssi = p_inq->rssi;result.inq_res.ble_addr_type = p_inq->ble_addr_type;result.inq_res.inq_result_type = p_inq->inq_result_type;result.inq_res.device_type = p_inq->device_type;result.inq_res.flag = p_inq->flag;/* application will parse EIR to find out remote device name */result.inq_res.p_eir = p_eir;result.inq_res.eir_len = eir_len;p_inq_info = BTM_InqDbRead(p_inq->remote_bd_addr);if (p_inq_info != NULL) {/* initialize remt_name_not_required to false so that we get the name by* default */result.inq_res.remt_name_not_required = false;}if (bta_dm_search_cb.p_search_cback)bta_dm_search_cb.p_search_cback(BTA_DM_INQ_RES_EVT, &result);if (p_inq_info) {/* application indicates if it knows the remote name, inside the callbackcopy that to the inquiry data base*/if (result.inq_res.remt_name_not_required)p_inq_info->appl_knows_rem_name = true;}
}

在这里把扫描的devices数据放到result里通过bta_dm_search_cb.p_search_cback(BTA_DM_INQ_RES_EVT, &result);回传。event是BTA_DM_INQ_RES_EVT，通过搜索BTA_DM_INQ_RES_EVT发现在system\bt\btif\src\btif_dm.cc中有一个bte_search_devices_evt方法

static void bte_search_devices_evt(tBTA_DM_SEARCH_EVT event,tBTA_DM_SEARCH* p_data) {uint16_t param_len = 0;if (p_data) param_len += sizeof(tBTA_DM_SEARCH);/* Allocate buffer to hold the pointers (deep copy). The pointers will point* to the end of the tBTA_DM_SEARCH */switch (event) {case BTA_DM_INQ_RES_EVT: {if (p_data->inq_res.p_eir) param_len += p_data->inq_res.eir_len;} break;case BTA_DM_DISC_RES_EVT: {if (p_data->disc_res.raw_data_size && p_data->disc_res.p_raw_data)param_len += p_data->disc_res.raw_data_size;} break;}BTIF_TRACE_DEBUG("%s event=%s param_len=%d", __func__,dump_dm_search_event(event), param_len);/* if remote name is available in EIR, set teh flag so that stack doesnt* trigger RNR */if (event == BTA_DM_INQ_RES_EVT)p_data->inq_res.remt_name_not_required =check_eir_remote_name(p_data, NULL, NULL);btif_transfer_context(btif_dm_search_devices_evt, (uint16_t)event, (char*)p_data, param_len,(param_len > sizeof(tBTA_DM_SEARCH)) ? search_devices_copy_cb : NULL);
}

这里当扫描到设备时，回调这个方法，将上下文从BTE切换到BTIF再调用btif_dm_search_devices_evt，将扫描到的设备通过HAL_CBACK方式返回

/******************************************************************************** Function         btif_dm_search_devices_evt** Description      Executes search devices callback events in btif context** Returns          void******************************************************************************/
static void btif_dm_search_devices_evt(uint16_t event, char* p_param) {tBTA_DM_SEARCH* p_search_data;BTIF_TRACE_EVENT("%s event=%s", __func__, dump_dm_search_event(event));switch (event) {case BTA_DM_DISC_RES_EVT: {p_search_data = (tBTA_DM_SEARCH*)p_param;/* Remote name update */if (strlen((const char*)p_search_data->disc_res.bd_name)) {bt_property_t properties[1];bt_status_t status;properties[0].type = BT_PROPERTY_BDNAME;properties[0].val = p_search_data->disc_res.bd_name;properties[0].len = strlen((char*)p_search_data->disc_res.bd_name);RawAddress& bdaddr = p_search_data->disc_res.bd_addr;status =btif_storage_set_remote_device_property(&bdaddr, &properties[0]);ASSERTC(status == BT_STATUS_SUCCESS,"failed to save remote device property", status);HAL_CBACK(bt_hal_cbacks, remote_device_properties_cb, status, &bdaddr,1, properties);}/* TODO: Services? */} break;
......省略
}

扫描到设备时，调用HAL_CBACK(bt_hal_cbacks, device_found_cb, num_properties, properties);

device_found_cb是device_found_callback方法，在packages\apps\Bluetooth\jni\com_android_bluetooth_btservice_AdapterService.cpp中实现

static void device_found_callback(int num_properties,bt_property_t* properties) {CallbackEnv sCallbackEnv(__func__);if (!sCallbackEnv.valid()) return;ScopedLocalRef<jbyteArray> addr(sCallbackEnv.get(), NULL);int addr_index;for (int i = 0; i < num_properties; i++) {if (properties[i].type == BT_PROPERTY_BDADDR) {addr.reset(sCallbackEnv->NewByteArray(properties[i].len));if (!addr.get()) {ALOGE("Address is NULL (unable to allocate) in %s", __func__);return;}sCallbackEnv->SetByteArrayRegion(addr.get(), 0, properties[i].len,(jbyte*)properties[i].val);addr_index = i;}}if (!addr.get()) {ALOGE("Address is NULL in %s", __func__);return;}ALOGV("%s: Properties: %d, Address: %s", __func__, num_properties,(const char*)properties[addr_index].val);remote_device_properties_callback(BT_STATUS_SUCCESS,(RawAddress*)properties[addr_index].val,num_properties, properties);sCallbackEnv->CallVoidMethod(sJniCallbacksObj, method_deviceFoundCallback,addr.get());
}

该方法对应JNI为method_deviceFoundCallback，即

  method_deviceFoundCallback =env->GetMethodID(jniCallbackClass, "deviceFoundCallback", "([B)V");

对应JniCallbacks.java中的deviceFoundCallback方法

deviceFoundCallback再将扫描到的广播发送出去

packages\apps\Bluetooth\src\com\android\bluetooth\btservice\RemoteDevices.java

    void deviceFoundCallback(byte[] address) {// The device properties are already registered - we can send the intent// nowBluetoothDevice device = getDevice(address);debugLog("deviceFoundCallback: Remote Address is:" + device);DeviceProperties deviceProp = getDeviceProperties(device);if (deviceProp == null) {errorLog("Device Properties is null for Device:" + device);return;}Intent intent = new Intent(BluetoothDevice.ACTION_FOUND);intent.putExtra(BluetoothDevice.EXTRA_DEVICE, device);intent.putExtra(BluetoothDevice.EXTRA_CLASS,new BluetoothClass(deviceProp.mBluetoothClass));intent.putExtra(BluetoothDevice.EXTRA_RSSI, deviceProp.mRssi);intent.putExtra(BluetoothDevice.EXTRA_NAME, deviceProp.mName);final ArrayList<DiscoveringPackage> packages = sAdapterService.getDiscoveringPackages();synchronized (packages) {for (DiscoveringPackage pkg : packages) {intent.setPackage(pkg.getPackageName());sAdapterService.sendBroadcastMultiplePermissions(intent, new String[]{AdapterService.BLUETOOTH_PERM, pkg.getPermission()});}}}