android4.3 Bluetooth(le)分析之startLeScan分析
BluetoothAdapter.java中有low enery(le)的一些方法，android提供了这些方法，但源码中并未找到这些方法的调用之处。本文档主要分析这类方法的执行流程，来了解下le到底做了些什么。
本文主要就是分析下startLeScan方法（两个重载方法）。
public boolean startLeScan(LeScanCallback callback) { return startLeScan(null, callback); } public boolean startLeScan(UUID[] serviceUuids, LeScanCallback callback) { if (DBG) Log.d(TAG, "startLeScan(): " + serviceUuids); synchronized(mLeScanClients) { if (mLeScanClients.containsKey(callback)) { if (DBG) Log.e(TAG, "LE Scan has already started"); return false; } try { //获取BluetoothGattBinder类的实例，该类的定义在GattService.java中 IBluetoothGatt iGatt = mManagerService.getBluetoothGatt(); if (iGatt == null) { // BLE is not supported return false; } UUID uuid = UUID.randomUUID(); GattCallbackWrapper wrapper = new GattCallbackWrapper(this, callback, serviceUuids); //重点分析该方法。作用是为本地设备进行注册，以及启动扫描 //wrapper是GattCallbackWrapper类的对象。该类注册了一些Gatt协议的回调方法 iGatt.registerClient(new ParcelUuid(uuid), wrapper); if (wrapper.scanStarted()) { mLeScanClients.put(callback, wrapper); return true; } } catch (RemoteException e) { Log.e(TAG,"",e); } } return false; }
下面来分析下iGatt.registerClient(new ParcelUuid(uuid), wrapper)方法，路径如下：(packages/apps/Bluetooth/src/com/android/bluetooth/gatt/GattService.java::BluetoothGattBinder)
public void registerClient(ParcelUuid uuid, IBluetoothGattCallback callback) { GattService service = getService(); if (service == null) return; service.registerClient(uuid.getUuid(), callback); }
接着会调用GattService服务的同名方法
void registerClient(UUID uuid, IBluetoothGattCallback callback) { enforceCallingOrSelfPermission(BLUETOOTH_PERM, "Need BLUETOOTH permission"); if (DBG) Log.d(TAG, "registerClient() - UUID=" + uuid); mClientMap.add(uuid, callback); gattClientRegisterAppNative(uuid.getLeastSignificantBits(), uuid.getMostSignificantBits()); }
接下来会调用jni层com_android_bluetooth_gatt.cpp文件中的gattClientRegisterAppNative方法。
static void gattClientRegisterAppNative(JNIEnv* env, jobject object, jlong app_uuid_lsb, jlong app_uuid_msb ){ bt_uuid_t uuid; if (!sGattIf) return; set_uuid(uuid.uu, app_uuid_msb, app_uuid_lsb); sGattIf->client->register_client(&uuid);}
分析sGattIf->client->register_client(&uuid);语句
(1)sGattIf是一个静态变量，定义是static const btgatt_interface_t *sGattIf = NULL;
又是这种类型的变量。第一反应就是去找btgatt_interface_t结构体定义的头文件(一般在hardware目录)，然后再搜索调用的c文件(一般在external/bluetooth/bluedroid，有时找到的c文件与头文件同名)。
btgatt_interface_t结构体的定义：hardware/libhardware/include/hardware/bt_gatt.h
/** Represents the standard Bluetooth GATT interface. */typedef struct { /** Set to sizeof(btgatt_interface_t) */ size_t size; /** * Initializes the interface and provides callback routines */ bt_status_t (*init)( const btgatt_callbacks_t* callbacks ); /** Closes the interface */ void (*cleanup)( void ); /** Pointer to the GATT client interface methods.*/ const btgatt_client_interface_t* client; /** Pointer to the GATT server interface methods.*/ const btgatt_server_interface_t* server;} btgatt_interface_t;
btgatt_interface_t结构体的对象：external/bluetooth/bluedroi/btif/src/btif_gatt.c
static const btgatt_interface_t btgattInterface = { sizeof(btgattInterface), btif_gatt_init, btif_gatt_cleanup, &btgattClientInterface, &btgattServerInterface, };
回到sGattIf->client->register_client(&uuid);语句，它调用了sGattIf结构体对象中的client对象的register_client函数，那么就是btgattClientInterface对象的register_client函数。
由结构体的定义可知client对象的类型是btgatt_client_interface_t结构体。同理分析可得以下结果，
btgatt_client_interface_t结构体的定义：hardware/libhardware/include/hardware/ bt_gatt_client.h
typedef struct { /** Registers a GATT client application with the stack */ bt_status_t (*register_client)( bt_uuid_t *uuid ); /** Unregister a client application from the stack */ bt_status_t (*unregister_client)(int client_if ); ......}
btgatt_client_interface_t结构体的对象：external/bluetooth/bluedroi/btif/src/btif_gatt_client.c
const btgatt_client_interface_t btgattClientInterface = { btif_gattc_register_app, btif_gattc_unregister_app, btif_gattc_scan, ......};
因此client->register_client就是调用了btif_gattc_register_app方法[-->btif_gatt_client.c]。
static bt_status_t btif_gattc_register_app(bt_uuid_t *uuid){ CHECK_BTGATT_INIT(); btif_gattc_cb_t btif_cb; memcpy(&btif_cb.uuid, uuid, sizeof(bt_uuid_t)); return btif_transfer_context(btgattc_handle_event, BTIF_GATTC_REGISTER_APP, (char*) &btif_cb, sizeof(btif_gattc_cb_t), NULL);}
分析btgattc_handle_event函数
static void btgattc_handle_event(uint16_t event, char* p_param){ ...... btif_gattc_cb_t* p_cb = (btif_gattc_cb_t*)p_param; if (!p_cb) return; switch (event) { case BTIF_GATTC_REGISTER_APP: btif_to_bta_uuid(&uuid, &p_cb->uuid); //为uuid注册回调函数 BTA_GATTC_AppRegister(&uuid, bte_gattc_cback); break; ....... }}
分析BTA_GATTC_AppRegister函数
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void BTA_GATTC_AppRegister(tBT_UUID *p_app_uuid, tBTA_GATTC_CBACK *p_client_cb) { tBTA_GATTC_API_REG *p_buf; /* register with BTA system manager */ GKI_sched_lock(); //注册Gatt客户端主事件处理函数bta_gattc_hdl_event，在bta_gatt_reg结构体中定义。 bta_sys_register(BTA_ID_GATTC, &bta_gatt_reg); GKI_sched_unlock(); if ((p_buf = (tBTA_GATTC_API_REG *) GKI_getbuf(sizeof(tBTA_GATTC_API_REG))) != NULL) { p_buf->hdr.event = BTA_GATTC_API_REG_EVT; if (p_app_uuid != NULL) memcpy(&p_buf->app_uuid, p_app_uuid, sizeof(tBT_UUID)); p_buf->p_cback = p_client_cb; bta_sys_sendmsg(p_buf); } return;}
(a)通过bta_sys_register函数注册了bta_gatt_reg结构体中定义的客户端主事件处理函数bta_gattc_hdl_event；然后设置event为BTA_GATTC_API_REG_EV，触发bta_gattc_hdl_event函数。
BOOLEAN bta_gattc_hdl_event(BT_HDR *p_msg){ tBTA_GATTC_CB *p_cb = &bta_gattc_cb; tBTA_GATTC_CLCB *p_clcb = NULL;#if BTA_GATT_DEBUG == TRUE APPL_TRACE_DEBUG1("bta_gattc_hdl_event: Event [%s]", gattc_evt_code(p_msg->event)); #endif switch (p_msg->event) { case BTA_GATTC_API_REG_EVT: bta_gattc_register(p_cb, (tBTA_GATTC_DATA *) p_msg); break; ...... }}
(b)调用bta_gattc_register函数。该函数用来注册一个客户端Gatt应用程序。
void bta_gattc_register(tBTA_GATTC_CB *p_cb, tBTA_GATTC_DATA *p_data){ ...... /* callback with register event */ if (p_data->api_reg.p_cback) { (*p_data->api_reg.p_cback)(BTA_GATTC_REG_EVT, (tBTA_GATTC *)&cb_data); }}
调用相关event(BTA_GATTC_REG_EVT)的回调函数。
到此，BTA_GATTC_AppRegister函数分析完毕，接下来分析BTA_GATTC_AppRegister(&uuid, bte_gattc_cback);中的参数部分。
ps:上述的回调函数就是这里的参数：bte_gattc_cback函数。那么BTA_GATTC_REG_EVT事件就调用该函数处理了。
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分析回调函数bte_gattc_cback
static void bte_gattc_cback(tBTA_GATTC_EVT event, tBTA_GATTC *p_data){ bt_status_t status = btif_transfer_context(btif_gattc_upstreams_evt, (uint16_t) event, (void*)p_data, sizeof(tBTA_GATTC), NULL); ASSERTC(status == BT_STATUS_SUCCESS, "Context transfer failed!", status);}
分析btif_gattc_upstreams_evt函数，在该函数中会处理BTA_GATTC_REG_EVT事件。
static void btif_gattc_upstreams_evt(uint16_t event, char* p_param){ tBTA_GATTC *p_data = (tBTA_GATTC*)p_param; switch (event) { case BTA_GATTC_REG_EVT: { bt_uuid_t app_uuid; bta_to_btif_uuid(&app_uuid, &p_data->reg_oper.app_uuid); HAL_CBACK(bt_gatt_callbacks, client->register_client_cb , p_data->reg_oper.status , p_data->reg_oper.client_if , &app_uuid ); break; } ...... }}
bt_gatt_callbacks对象的类型是btgatt_callbacks_t，其定义在hardware/libhardware/include/hardware/bt_gatt.h文件中。现在对bt_gatt_callbacks对象从头开始分析其来源。
在GattService.java::start()方法中，调用了initializeNative方法。继而调用JNI层initializeNative方法。贴出该方法。
static const btgatt_interface_t *sGattIf = NULL;static const bt_interface_t* btIf;......static void initializeNative(JNIEnv *env, jobject object) { /* getBluetoothInterface 函数返回sBluetoothInterface对象，在android4.3 bt 扫描分析.docx中已说明该对象的来源*/ if ( (btIf = getBluetoothInterface()) == NULL) { error("Bluetooth module is not loaded"); return; } ...... //(a) // BT_PROFILE_GATT_ID的值是”gatt” if ( (sGattIf = (btgatt_interface_t *) btIf->get_profile_interface(BT_PROFILE_GATT_ID)) == NULL) { error("Failed to get Bluetooth GATT Interface"); return; } bt_status_t status; //(b) /* sGattCallbacks的定义 static const btgatt_callbacks_t sGattCallbacks = { sizeof(btgatt_callbacks_t), &sGattClientCallbacks, &sGattServerCallbacks };*/ if ( (status = sGattIf->init(&sGattCallbacks)) != BT_STATUS_SUCCESS) { error("Failed to initialize Bluetooth GATT, status: %d", status); sGattIf = NULL; return; } mCallbacksObj = env->NewGlobalRef(object);}
(a) 分析
static const void* get_profile_interface (const char *profile_id){ ......#if BTA_GATT_INCLUDED == TRUE if (is_profile(profile_id, BT_PROFILE_GATT_ID)) return btif_gatt_get_interface();#endif return NULL;}
分析btif_gatt_get_interface函数
const btgatt_interface_t *btif_gatt_get_interface(){ return &btgattInterface;}
btgattInterface对象的类型是btgatt_interface_t结构体。再贴一遍该结构体的定义，如下：
typedef struct { /** Set to sizeof(btgatt_interface_t) */ size_t size; /** * Initializes the interface and provides callback routines */ bt_status_t (*init)( const btgatt_callbacks_t* callbacks ); /** Closes the interface */ void (*cleanup)( void ); /** Pointer to the GATT client interface methods.*/ const btgatt_client_interface_t* client; /** Pointer to the GATT server interface methods.*/ const btgatt_server_interface_t* server;} btgatt_interface_t;
另，btgattInterface对象定义如下：
static const btgatt_interface_t btgattInterface = { sizeof(btgattInterface), btif_gatt_init, btif_gatt_cleanup, &btgattClientInterface, &btgattServerInterface,};
所以sGattIf 就是btgattInterface对象。
(b) 接下来调用sGattIf->init函数。由上可知，即为btif_gatt_init函数。
static bt_status_t btif_gatt_init( const btgatt_callbacks_t* callbacks ){ /*bt_gatt_callbacks由参数赋值，该参数是sGattCallbacks。 sGattCallbacks的定义 static const btgatt_callbacks_t sGattCallbacks = { sizeof(btgatt_callbacks_t), &sGattClientCallbacks, &sGattServerCallbacks };*/ bt_gatt_callbacks = callbacks; BTA_GATTC_Init(); BTA_GATTS_Init(); return BT_STATUS_SUCCESS;}
到此为止，调用语句中bt_gatt_callbacks对象我们已经清楚了，就是sGattCallbacks对象。现在分析client->register_client_cb。
HAL_CBACK(bt_gatt_callbacks, client->register_client_cb , p_data->reg_oper.status , p_data->reg_oper.client_if , &app_uuid );
client对象是在btgatt_callbacks_t结构体中定义的一个变量，其初始化是在bt_gatt_callbacks对象（即sGattCallbacks对象）中。
btgatt_callbacks_t结构体如下：
typedef struct { /** Set to sizeof(btgatt_callbacks_t) */ size_t size; /** GATT Client callbacks */ const btgatt_client_callbacks_t* client; /** GATT Server callbacks */ const btgatt_server_callbacks_t* server;} btgatt_callbacks_t;
因此client对应的就是sGattCallbacks对象中的sGattClientCallbacks对象。sGattClientCallbacks对象定义如下(在JNI层的com_android_bluetooth_gatt.cpp文件中定义)：
static const btgatt_client_callbacks_t sGattClientCallbacks = { btgattc_register_app_cb, btgattc_scan_result_cb, ......};
而sGattClientCallbacks对象的类型是btgatt_client_callbacks_t结构体，如下
typedef struct { register_client_callback register_client_cb; scan_result_callback scan_result_cb; connect_callback open_cb; disconnect_callback close_cb; ...... } btgatt_client_callbacks_t;
因此，client->register_client_cb就是调用了sGattClientCallbacks 对象中的btgattc_register_app_cb函数。
void btgattc_register_app_cb(int status, int clientIf, bt_uuid_t *app_uuid){ CHECK_CALLBACK_ENV sCallbackEnv->CallVoidMethod(mCallbacksObj, method_onClientRegistered, status, clientIf, UUID_PARAMS(app_uuid)); checkAndClearExceptionFromCallback(sCallbackEnv, __FUNCTION__);}
JNI层的method_onClientRegistered 函数对应java层的onClientRegistered方法[-->GattService.java]。
void onClientRegistered(int status, int clientIf, long uuidLsb, long uuidMsb) throws RemoteException { UUID uuid = new UUID(uuidMsb, uuidLsb); if (DBG) Log.d(TAG, "onClientRegistered() - UUID=" + uuid + ", clientIf=" + clientIf); ClientMap.App app = mClientMap.getByUuid(uuid); if (app != null) { app.id = clientIf; app.linkToDeath(new ClientDeathRecipient(clientIf)); app.callback.onClientRegistered(status, clientIf); } }
此callback其实是GattCallbackWrapper类的对象。
分析mClientMap对象，在registerClient方法中调用了ClientMap的父类ContextMap::add方法，将GattCallbackWrapper类对象wrapper作为callback参数添加到mClientMap对象中。
接下来重新分析：
onClientRegistered方法[--->BluetoothAdapter::GattCallbackWrapper类]
public void onClientRegistered(int status, int clientIf) { if (DBG) Log.d(TAG, "onClientRegistered() - status=" + status + " clientIf=" + clientIf); synchronized(this) { if (mLeHandle == -1) { if (DBG) Log.d(TAG, "onClientRegistered LE scan canceled"); } if (status == BluetoothGatt.GATT_SUCCESS) { mLeHandle = clientIf; IBluetoothGatt iGatt = null; try { BluetoothAdapter adapter = mBluetoothAdapter.get(); if (adapter != null) { iGatt = adapter.getBluetoothManager().getBluetoothGatt(); //调用startLeScan方法时，传递过来的参数为null，执行此处 if (mScanFilter == null) { iGatt.startScan(mLeHandle, false); } else { ParcelUuid[] uuids = new ParcelUuid[mScanFilter.length]; for(int i = 0; i != uuids.length; ++i) { uuids[i] = new ParcelUuid(mScanFilter[i]); } iGatt.startScanWithUuids(mLeHandle, false, uuids); } } else { Log.e(TAG, "onClientRegistered, BluetoothAdapter null"); mLeHandle = -1; } } catch (RemoteException e) { Log.e(TAG, "fail to start le scan: " + e); mLeHandle = -1; } ...... }
接下来分析startScan方法，在GattService.java中。
void startScan(int appIf, boolean isServer) { ...... if (getScanClient(appIf, isServer) == null) { if (DBG) Log.d(TAG, "startScan() - adding client=" + appIf); mScanQueue.add(new ScanClient(appIf, isServer)); } gattClientScanNative(appIf, true); }
JNI层gattClientScanNative函数
static void gattClientScanNative(JNIEnv* env, jobject object, jint clientIf, jboolean start){ if (!sGattIf) return; sGattIf->client->scan(clientIf, start);}
同之前分析register_client的步骤，分析的scan函数对应btif_gattc_scan函数。
static bt_status_t btif_gattc_scan( int client_if, bool start ){ CHECK_BTGATT_INIT(); btif_gattc_cb_t btif_cb; btif_cb.client_if = (uint8_t) client_if; return btif_transfer_context(btgattc_handle_event, start ? BTIF_GATTC_SCAN_START : BTIF_GATTC_SCAN_STOP, (char*) &btif_cb, sizeof(btif_gattc_cb_t), NULL);}
在btgattc_handle_event函数中处理BTIF_GATTC_SCAN_START事件
case BTIF_GATTC_SCAN_START: btif_gattc_init_dev_cb(); // BTA_DmBleObserve发出消息，包含BTA_DM_API_BLE_OBSERVE_EVT事件 BTA_DmBleObserve(TRUE, 0, bte_scan_results_cb); break;
调用bte_scan_results_cb函数，
static void bte_scan_results_cb (tBTA_DM_SEARCH_EVT event, tBTA_DM_SEARCH *p_data){ btif_gattc_cb_t btif_cb; uint8_t len; switch (event) { case BTA_DM_INQ_RES_EVT: ...... case BTA_DM_INQ_CMPL_EVT: ...... btif_transfer_context(btif_gattc_upstreams_evt, BTIF_GATT_OBSERVE_EVT, (char*) &btif_cb, sizeof(btif_gattc_cb_t), NULL);}
在btif_gattc_upstreams_evt函数中处理BTIF_GATT_OBSERVE_EVT事件。
case BTIF_GATT_OBSERVE_EVT: { btif_gattc_cb_t *p_btif_cb = (btif_gattc_cb_t*)p_param; if (!btif_gattc_find_bdaddr(p_btif_cb->bd_addr.address)) { btif_gattc_add_remote_bdaddr(p_btif_cb->bd_addr.address, p_btif_cb->addr_type); btif_gattc_update_properties(p_btif_cb); } HAL_CBACK(bt_gatt_callbacks, client->scan_result_cb, &p_btif_cb->bd_addr, p_btif_cb->rssi, p_btif_cb->value); break; }
同分析register_client_cb函数，在JNI层com_android_bluetooth_gatt.cpp文件中定义，分析得scan_result_cb对应函数btgattc_scan_result_cb。
void btgattc_scan_result_cb(bt_bdaddr_t* bda, int rssi, uint8_t* adv_data){ ...... sCallbackEnv->CallVoidMethod(mCallbacksObj, method_onScanResult , address, rssi, jb); ......}
对应java层文件GattService类onScanResult方法。
void onScanResult(String address, int rssi, byte[] adv_data) { for (ScanClient client : mScanQueue) { ...... if (!client.isServer) { ClientMap.App app = mClientMap.getById(client.appIf); if (app != null) { try { app.callback.onScanResult(address, rssi, adv_data); } catch (RemoteException e) { Log.e(TAG, "Exception: " + e); mClientMap.remove(client.appIf); mScanQueue.remove(client); } } } ...... } }
callback为GattCallbackWrapper类的对象，因此调用GattCallbackWrapper类中的onScanResult方法。
public void onScanResult(String address, int rssi, byte[] advData) { ...... try { BluetoothAdapter adapter = mBluetoothAdapter.get(); if (adapter == null) { Log.d(TAG, "onScanResult, BluetoothAdapter null"); return; } mLeScanCb.onLeScan(adapter.getRemoteDevice(address), rssi, advData); } catch (Exception ex) { Log.w(TAG, "Unhandled exception: " + ex); } }
mLeScanCb对象为LeScanCallback接口的对象，不过源码中并没有类来实现该接口，故只能分析到这里了。扫描到此结束，over~~
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贴出流程图，see see，5个步骤：
1.startLeScan(JAVA-->JNI)
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2.startLeScan(蓝牙栈)
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3.startLeScan(JNI-->JAVA)
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4.startLeScan(蓝牙栈)
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5.startLeScan(JNI-->JAVA)
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