1. Bluetooth Enable Overview
1.1 Bluetooth Enable Entrance
packages/apps/Bluetooth/src/com/android/bluetooth/btservice/AdapterService.java
public static class AdapterServiceBinder extends IBluetooth.Stub {
@Override
public boolean enable(boolean quietMode) {
AdapterService service = getService();
......
return service.enable(quietMode);
}
}
public synchronized boolean enable(boolean quietMode) {
......
mQuietmode = quietMode; // 由上层传递，测试设备的值 false
mAdapterStateMachine.sendMessage(AdapterState.BLE_TURN_ON);
return true;
}
1.2 Bluetooth StateMachine Overview
packages/apps/Bluetooth/src/com/android/bluetooth/btservice/AdapterState.java
根据源码注释可知，蓝牙开启的状态转换关系如下图：
蓝牙启动的状态机转换图.png
由上图可知，经历 Off、TurningBleOn、BleOn、TurningOn、On 共五个状态，蓝牙处于完全的开启状态。
五个状态中，仅仅 TurningBleOn 和 TurningOn 是不稳定状态，无论操作成功与否都需要恢复到稳定状态 Off、BleOn、On 三种状态中的一种。
下面开始分析蓝牙 enable 整体流程，分为 TurningBleOn 和 TurningOn 两个流程分析。
首先整体介绍 enable 流程中状态机的转化，再分析 TurningBleOn，最后分析 TurningOn。
packages/apps/Bluetooth/src/com/android/bluetooth/btservice/AdapterState.java
final class AdapterState extends StateMachine {
// 所有状态的基类
private abstract class BaseAdapterState extends State {
abstract int getStateValue();
// 进入所有的具体状态时，需要更新状态信息。（若子类未重写）
@Override
public void enter() {
int currState = getStateValue();
mAdapterService.updateAdapterState(mPrevState, currState); // 0
mPrevState = currState;
}
......
}
private class OffState extends BaseAdapterState {
@Override
public boolean processMessage(Message msg) {
switch (msg.what) {
case BLE_TURN_ON:
transitionTo(mTurningBleOnState); // 1
break;
}
return true;
}
}
private class TurningBleOnState extends BaseAdapterState {
@Override
public void enter() {
super.enter();
sendMessageDelayed(BLE_START_TIMEOUT, BLE_START_TIMEOUT_DELAY);
mAdapterService.bringUpBle(); // 2
}
@Override
public boolean processMessage(Message msg) {
switch (msg.what) {
case BLE_STARTED:
transitionTo(mBleOnState); // 3
break;
......
}
return true;
}
}
private class BleOnState extends BaseAdapterState {
@Override
public boolean processMessage(Message msg) {
switch (msg.what) {
case USER_TURN_ON:
transitionTo(mTurningOnState); // 4
break;
......
}
return true;
}
}
private class TurningOnState extends BaseAdapterState {
@Override
public void enter() {
super.enter();
sendMessageDelayed(BREDR_START_TIMEOUT, BREDR_START_TIMEOUT_DELAY);
mAdapterService.startProfileServices(); // 5
}
@Override
public boolean processMessage(Message msg) {
switch (msg.what) {
case BREDR_STARTED:
transitionTo(mOnState); // 6
break;
......
}
return true;
}
}
private class OnState extends BaseAdapterState {
@Override
public boolean processMessage(Message msg) {
switch (msg.what) {
case USER_TURN_OFF:
transitionTo(mTurningOffState);
break;
}
return true;
}
}
}
从以上 0~6 共计 7 个数字注释可知，除了状态转移，状态机主要执行三个方法：
- mAdapterService.updateAdapterState(mPrevState, currState); 【//0，通用方法】
- mAdapterService.bringUpBle(); 【//2， TurningBleOn】
- mAdapterService.startProfileServices(); 【// 5，TurningOn】
状态机的状态流转过程中会先后执行 bringUpBle() 和 startProfileServices()，但此处还没有涉及到这些方法是如何被触发的，后续需要将这些内容连贯起来。
updateAdapterState() 方法是状态机的通用方法。先分析其处理流程，再分析状态机的状态变化流程。
2. Bluetooth StateMachine State Update - updateAdapterState()
packages/apps/Bluetooth/src/com/android/bluetooth/btservice/AdapterService.java
void updateAdapterState(int prevState, int newState) {
mAdapterProperties.setState(newState);
invalidateBluetoothGetStateCache();
if (mCallbacks != null) {
int n = mCallbacks.beginBroadcast();
for (int i = 0; i < n; i++) {
try {
mCallbacks.getBroadcastItem(i).onBluetoothStateChange(prevState, newState);
} catch (RemoteException e) {
......
}
}
mCallbacks.finishBroadcast();
}
// Turn the Adapter all the way off if we are disabling and the snoop log setting changed.
if (newState == BluetoothAdapter.STATE_BLE_TURNING_ON) {
mSnoopLogSettingAtEnable =
SystemProperties.get(BLUETOOTH_BTSNOOP_LOG_MODE_PROPERTY, "empty");
mDefaultSnoopLogSettingAtEnable =
Settings.Global.getString(getContentResolver(),
Settings.Global.BLUETOOTH_BTSNOOP_DEFAULT_MODE);
SystemProperties.set(BLUETOOTH_BTSNOOP_DEFAULT_MODE_PROPERTY,
mDefaultSnoopLogSettingAtEnable);
} else if (newState == BluetoothAdapter.STATE_BLE_ON
&& prevState != BluetoothAdapter.STATE_OFF) {
String snoopLogSetting =
SystemProperties.get(BLUETOOTH_BTSNOOP_LOG_MODE_PROPERTY, "empty");
String snoopDefaultModeSetting =
Settings.Global.getString(getContentResolver(),
Settings.Global.BLUETOOTH_BTSNOOP_DEFAULT_MODE);
if (!TextUtils.equals(mSnoopLogSettingAtEnable, snoopLogSetting)
|| !TextUtils.equals(mDefaultSnoopLogSettingAtEnable,
snoopDefaultModeSetting)) {
mAdapterStateMachine.sendMessage(AdapterState.BLE_TURN_OFF);
}
}
}
3. bringUpBle
packages/apps/Bluetooth/src/com/android/bluetooth/btservice/AdapterService.java
void bringUpBle() {
if (getResources().getBoolean(
R.bool.config_bluetooth_reload_supported_profiles_when_enabled)) {
Config.init(getApplicationContext());
}
mRemoteDevices.reset();
mAdapterProperties.init(mRemoteDevices);
mBondStateMachine = BondStateMachine.make(this, mAdapterProperties, mRemoteDevices);
mJniCallbacks.init(mBondStateMachine, mRemoteDevices);
try {
mBatteryStats.noteResetBleScan();
} catch (RemoteException e) {
Log.w(TAG, "RemoteException trying to send a reset to BatteryStats");
}
// 5 Start Gatt service
setProfileServiceState(GattService.class, BluetoothAdapter.STATE_ON);
}
3.1 RemoteDevices
3.2 AdapterProperties
3.3 BondStateMachine
3.4 JniCallbacks
3.5 GattService Initialization
GattService 初始化详情：GattService Initialization
根据 GattService 的基类初始化 ProfileService Initialization 的内容可知，Profile 启动之后，在AdapterService 中会记录状态以及可能会触发后续的 蓝牙enable 流程。
packages/apps/Bluetooth/src/com/android/bluetooth/btservice/AdapterService.java
public class AdapterService extends Service {
private void processProfileServiceStateChanged(ProfileService profile, int state) {
switch (state) {
case BluetoothAdapter.STATE_ON:
......
if (GattService.class.getSimpleName().equals(profile.getName())) {
// 启动 GATT service 时，走该分支，继续执行 enable
enableNative();
} else if (mRegisteredProfiles.size() == Config.getSupportedProfiles().length
&& mRegisteredProfiles.size() == mRunningProfiles.size()) {
// 所有支持的 profile service 启动后，走该分支
......
}
break;
......
}
}
}
}
以上代码内容，不仅是 ProfileService 的通用流程，还是蓝牙enable的整体流程的内容。
- 若 GattService 启动完成，则执行 enableNative()，详情：Bluetooth initialization - enable in Bluetooth process - Native(Cpp) ；
- 若所有支持的 profile 启动完成，则执行另外一个分支，具体内容在下文介绍。
4. startProfileServices
void startProfileServices() {
Class[] supportedProfileServices = Config.getSupportedProfiles();
if (supportedProfileServices.length == 1 && GattService.class.getSimpleName()
.equals(supportedProfileServices[0].getSimpleName())) {
...... // 设备只支持 BLE 时走这里，不分析此路径
} else {
setAllProfileServiceStates(supportedProfileServices, BluetoothAdapter.STATE_ON);
}
}
private void setAllProfileServiceStates(Class[] services, int state) {
for (Class service : services) {
if (GattService.class.getSimpleName().equals(service.getSimpleName())) {
continue; // GattService 已经初始化过了，排除之
}
setProfileServiceState(service, state);
}
}
01-15 21:33:43.404 31081 31081 V AdapterServiceConfig: Adding HeadsetService
01-15 21:33:43.404 31081 31081 V AdapterServiceConfig: Adding A2dpService
01-15 21:33:43.404 31081 31081 V AdapterServiceConfig: Adding HidHostService
01-15 21:33:43.404 31081 31081 V AdapterServiceConfig: Adding PanService
01-15 21:33:43.404 31081 31081 V AdapterServiceConfig: Adding GattService
01-15 21:33:43.404 31081 31081 V AdapterServiceConfig: Adding BluetoothMapService
01-15 21:33:43.404 31081 31081 V AdapterServiceConfig: Adding AvrcpTargetService
01-15 21:33:43.404 31081 31081 V AdapterServiceConfig: Adding SapService
01-15 21:33:43.404 31081 31081 V AdapterServiceConfig: Adding HidDeviceService
01-15 21:33:43.404 31081 31081 V AdapterServiceConfig: Adding BluetoothOppService
01-15 21:33:43.404 31081 31081 V AdapterServiceConfig: Adding BluetoothPbapService
01-15 21:33:43.404 31081 31081 V AdapterServiceConfig: Adding HearingAidService
Android 11 Pixel5 在蓝牙进程初始化时会添加以上这些Service，此处会分别初始化它们（除 GattService之外，GattService 在 bingUpBle 阶段初始化）。
Profiles 的初始化过程如下：
Profile Initialization - HeadsetService
Profile Initialization - A2dpService
Profile Initialization - HidHostService
Profile Initialization - HidDeviceService
Profile Initialization - PanService
Profile Initialization - SapService
Profile Initialization - AvrcpTargetService
Profile Initialization - BluetoothMapService
Profile Initialization - BluetoothPbapService
Profile Initialization - BluetoothOppService
Profile Initialization - HearingAidService
当所有支持的 Profile 全部注册并启动之后，执行
packages/apps/Bluetooth/src/com/android/bluetooth/btservice/AdapterService.java
public class AdapterService extends Service {
private void processProfileServiceStateChanged(ProfileService profile, int state) {
switch (state) {
case BluetoothAdapter.STATE_ON:
......
if (GattService.class.getSimpleName().equals(profile.getName())) {
// 启动 GATT service 时，走该分支，继续执行 enable
......
} else if (mRegisteredProfiles.size() == Config.getSupportedProfiles().length
&& mRegisteredProfiles.size() == mRunningProfiles.size()) {
// 所有支持的 profile service 启动后，走该分支
mAdapterProperties.onBluetoothReady();
updateUuids();
setBluetoothClassFromConfig();
initProfileServices();
getAdapterPropertyNative(AbstractionLayer.BT_PROPERTY_LOCAL_IO_CAPS);
getAdapterPropertyNative(AbstractionLayer.BT_PROPERTY_LOCAL_IO_CAPS_BLE);
mAdapterStateMachine.sendMessage(AdapterState.BREDR_STARTED);
}
break;
......
}
}
}
}
若所有支持的 profile 启动完成，则执行一些其他的初始化操作。
随后向状态机发送 BREDR_STARTED 消息，状态机进入 OnState。
5. Summary
经过以上分析，蓝牙初始化整体架构如下图：
Android Bluetooth Enable Arch
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