蓝牙打开流程-从APP层的分析
1 蓝牙服务的启动
蓝牙服务作为系统服务，启动是从systemserver里面启动的，systemserver里面的main方法被调用，该方法运行run方法，代码如下所示：
public static void main(String[] args) {
new SystemServer().run();
}if (isEmulator) {
Slog.i(TAG, "No Bluetooh Service (emulator)");
} else if (mFactoryTestMode == FactoryTest.FACTORY_TEST_LOW_LEVEL) {
Slog.i(TAG, "No Bluetooth Service (factory test)");
} else if (!context.getPackageManager().hasSystemFeature
(PackageManager.FEATURE_BLUETOOTH)) {
Slog.i(TAG, "No Bluetooth Service (Bluetooth Hardware Not Present)");
} else if (disableBluetooth) {
Slog.i(TAG, "Bluetooth Service disabled by config");
} else {
Slog.i(TAG, "Bluetooth Service");
mSystemServiceManager.startService(BluetoothService.class); // 启动蓝牙服务bluetoothservice里面的onstart方法是将蓝牙服务注册到servicemanager，如下代码
public BluetoothService(Context context) {
super(context);
mBluetoothManagerService = new BluetoothManagerService(context);
//构造BluetoothManagerService对象
}
@Override
public void onStart() {
Log.d(TAG, "onStart: publishing BluetoothManagerService");
publishBinderService(BluetoothAdapter.BLUETOOTH_MANAGER_SERVICE, mBluetoothManagerService);// 将蓝牙服务注册到servicemanager
}至此，蓝牙服务已经启动，即蓝牙服务已经被注册到servicemanager里面了，使用蓝牙服务的时候，调用getsystemservice方法获取蓝牙服务的binder引用。
2 打开蓝牙
不管是第三方应用，还是用户从设置，systemui打开蓝牙，最终调用到BluetoothManagerService里面的enable方法
在该函数中，会向BluetoothHandler发送MESSAGE_ENABLE消息，在BluetoothHandler中处理MESSAGE_ENABLE消息
处理
MESSAGE_ENABLE消息的方法是handleEnable,handleEnable方法的代码如下：
private void handleEnable(boolean quietMode) {
mQuietEnable = quietMode;
synchronized(mConnection) {
if ((mBluetooth == null) && (!mBinding)) {
//Start bind timeout and bind
Message timeoutMsg=mHandler.obtainMessage(MESSAGE_TIMEOUT_BIND);
mHandler.sendMessageDelayed(timeoutMsg,TIMEOUT_BIND_MS);
mConnection.setGetNameAddressOnly(false);
Intent i = new Intent(IBluetooth.class.getName());
if (!doBind(i, mConnection,Context.BIND_AUTO_CREATE | Context.BIND_IMPORTANT,
UserHandle.CURRENT)) {
mHandler.removeMessages(MESSAGE_TIMEOUT_BIND);
} else {
mBinding = true;
}
} else if (mBluetooth != null) {
if (mConnection.isGetNameAddressOnly()) {
// if GetNameAddressOnly is set, we can clear this flag,
// so the service won't be unbind
// after name and address are saved
mConnection.setGetNameAddressOnly(false);
//Register callback object
try {
mBluetooth.registerCallback(mBluetoothCallback);
} catch (RemoteException re) {
Log.e(TAG, "Unable to register BluetoothCallback",re);
}
//Inform BluetoothAdapter instances that service is up
sendBluetoothServiceUpCallback();
}
//Enable bluetooth
try {
if (!mQuietEnable) {
if(!mBluetooth.enable()) {
Log.e(TAG,"IBluetooth.enable() returned false");
}
}
else {
if(!mBluetooth.enableNoAutoConnect()) {
Log.e(TAG,"IBluetooth.enableNoAutoConnect() returned false");
}
}
} catch (RemoteException e) {
Log.e(TAG,"Unable to call enable()",e);
}
}
}
}会走入上面的第一个if分支，绑定一个服务，这个服务是AdapterService,当这个服务绑定成功后，会回调onServiceConnected方法
public void onServiceConnected(ComponentName className, IBinder service) {
if (DBG) Log.d(TAG, "BluetoothServiceConnection: " + className.getClassName());
Message msg = mHandler.obtainMessage(MESSAGE_BLUETOOTH_SERVICE_CONNECTED);
// TBD if (className.getClassName().equals(IBluetooth.class.getName())) {
if (className.getClassName().equals("com.android.bluetooth.btservice.AdapterService")) {
msg.arg1 = SERVICE_IBLUETOOTH;
// } else if (className.getClassName().equals(IBluetoothGatt.class.getName())) {
} else if (className.getClassName().equals("com.android.bluetooth.gatt.GattService")) {
msg.arg1 = SERVICE_IBLUETOOTHGATT;
} else {
Log.e(TAG, "Unknown service connected: " + className.getClassName());
return;
}
msg.obj = service;
mHandler.sendMessage(msg);
}由于绑定的是adapterservice服务，所以会走到第二个分支，第一个分支是BLE相关的，即msg.arg1的值为1，在该回调方法中会发送一个MESSAGE_BLUETOOTH_SERVICE_CONNECTED消息，在处理MESSAGE_BLUETOOTH_SERVICE_CONNECTED消息的时候，会调用到adapterservice文件里面的enable方法。
public synchronized boolean enable(boolean quietMode) {
enforceCallingOrSelfPermission(BLUETOOTH_ADMIN_PERM, "Need BLUETOOTH ADMIN permission");
debugLog("enable() - Enable called with quiet mode status = " + mQuietmode);
mQuietmode = quietMode;
Message m = mAdapterStateMachine.obtainMessage(AdapterState.BLE_TURN_ON);
mAdapterStateMachine.sendMessage(m);
return true;
}
在该方法中，会给adapter状态机发送BLE_TURN_ON消息，看看处理BLE_TURN_ON消息的地方
case BLE_TURN_ON:
notifyAdapterStateChange(BluetoothAdapter.STATE_BLE_TURNING_ON);
mPendingCommandState.setBleTurningOn(true);
transitionTo(mPendingCommandState);
sendMessageDelayed(BLE_START_TIMEOUT, BLE_START_TIMEOUT_DELAY);
adapterService.BleOnProcessStart();
break;这段代码实现的功能是启动GattService。当GattService服务启动完成后，也会回调onServiceConnected方法，在该方法中也会发送MESSAGE_BLUETOOTH_SERVICE_CONNECTED，这个时候的msg.arg1的值为2. 看看处理MESSAGE_BLUETOOTH_SERVICE_CONNECTED的地方，在BluetoothManagerService里面
case MESSAGE_BLUETOOTH_SERVICE_CONNECTED:
{
if (DBG) Log.d(TAG,"MESSAGE_BLUETOOTH_SERVICE_CONNECTED: " + msg.arg1);
IBinder service = (IBinder) msg.obj;
synchronized(mConnection) {
if (msg.arg1 == SERVICE_IBLUETOOTHGATT) {
mBluetoothGatt = IBluetoothGatt.Stub.asInterface(service);
onBluetoothGattServiceUp();
break;
} // else must be SERVICE_IBLUETOOTH由上面的分支可知，是满足代码中的if条件的，这个时候将调用onBluetoothGattServiceUp方法，在这个方法中会调用adapterservice的onLeServiceUp方法，该方法中会发送USER_TURN_ON消息。
public void onLeServiceUp() {
Message m = mAdapterStateMachine.obtainMessage(AdapterState.USER_TURN_ON);
mAdapterStateMachine.sendMessage(m);
}看看处理这个消息的地方
switch(msg.what) {
case USER_TURN_ON:
notifyAdapterStateChange(BluetoothAdapter.STATE_TURNING_ON);
mPendingCommandState.setTurningOn(true);
transitionTo(mPendingCommandState);
sendMessageDelayed(BREDR_START_TIMEOUT, BREDR_START_TIMEOUT_DELAY);
adapterService.startCoreServices();
break;在处理这个消息的时候，会调用adapterservice中的startCoreServices方法。
void startCoreServices()
{
debugLog("startCoreServices()");
Class[] supportedProfileServices = Config.getSupportedProfiles();
//Start profile services
if (!mProfilesStarted && supportedProfileServices.length >0) {
//Startup all profile services
setProfileServiceState(supportedProfileServices,BluetoothAdapter.STATE_ON);
}else {
debugLog("startCoreProfiles(): Profile Services alreay started");
mAdapterStateMachine.sendMessage(mAdapterStateMachine.obtainMessage(AdapterState.BREDR_STARTED));
}
}在该方法中启动蓝牙的服务，
Starting service com.android.bluetooth.hfp.HeadsetService
Starting service com.android.bluetooth.a2dp.A2dpService
Starting service com.android.bluetooth.hid.HidService
Starting service com.android.bluetooth.hdp.HealthService
Starting service com.android.bluetooth.pan.PanService
Starting service com.android.bluetooth.map.BluetoothMapService
Starting service com.android.bluetooth.sap.SapService
Starting service com.android.bluetooth.opp.BluetoothOppService
Starting service com.android.bluetooth.pbap.BluetoothPbapService