首先我们要知道，主要系统服务都是在 SystemServer 启动的，蓝牙也是如此：
1、SystemServer
源码路径：/frameworks/base/services/java/com/android/server/SystemServer.java
private void startOtherServices(@NonNull TimingsTraceAndSlog t) {
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 {
t.traceBegin("StartBluetoothService");
mSystemServiceManager.startService(BluetoothService.class);
t.traceEnd();
}
}
SystemServer 在启动其他服务的方法里，启动了 BluetoothService。
2、BluetoothService
class BluetoothService extends SystemService {
private BluetoothManagerService mBluetoothManagerService;
public BluetoothService(Context context) {
super(context);
//创建BluetoothManagerService的实例
mBluetoothManagerService = new BluetoothManagerService(context);
}
......
@Override
public void onBootPhase(int phase) {
if (phase == SystemService.PHASE_SYSTEM_SERVICES_READY) {
//将BluetoothManagerService实例发布到系统中，这样就可以Context根据BT的service名去获取它的Binder代理操作API了
publishBinderService(BluetoothAdapter.BLUETOOTH_MANAGER_SERVICE,
mBluetoothManagerService);
} else if (phase == SystemService.PHASE_ACTIVITY_MANAGER_READY) {
//此时系统应该启动到一个比较晚的阶段了，可以使用AMS去Bind需要的Service了
mBluetoothManagerService.handleOnBootPhase();
}
}
......
}
可以看到，真正获取的服务是BluetoothManagerService 而非 BluetoothService。可以通过 ServiceManager.getService(BLUETOOTH_MANAGER _SERVICE) 获取蓝牙服务。
onBootPhase(int)：这个函数应该是 systemserver 在启动的时候会多次调用，参数代表当前启动进行到了什么阶段，用户定义的 service 针对各个阶段需要做怎样的处理或者是不做任何处理。
3、BluetoothManagerService
BluetoothManagerService(Context context) {
//创建内部处理msg的handler
mHandler = new BluetoothHandler(IoThread.get().getLooper());
mContext = context;
......
//false表示此次enable需要触发auto connect device和保存状态,BluetoothAdapter::enableNoAutoConnect()可以改变此状态
mQuietEnableExternal = false;
mEnableExternal = false;
......
IntentFilter filter = new IntentFilter();
//监听App通过接口修改BT 名称的广播
filter.addAction(BluetoothAdapter.ACTION_LOCAL_NAME_CHANGED);
//监听bt地址改变的广播
filter.addAction(BluetoothAdapter.ACTION_BLUETOOTH_ADDRESS_CHANGED);
//监听当前设置需要restore回上一次设置的广播,此时需要重新保存name和addr为上一次的信息
filter.addAction(Intent.ACTION_SETTING_RESTORED);
filter.setPriority(IntentFilter.SYSTEM_HIGH_PRIORITY);
mContext.registerReceiver(mReceiver, filter);
//从数据库中加载本机Bt的local name和address
loadStoredNameAndAddress();
//查看上一次关机时,BT是否为enable状态;如果是,这次开机也需要enable BT
if (isBluetoothPersistedStateOn()) {
if (DBG) {
Slog.d(TAG, "Startup: Bluetooth persisted state is ON.");
}
mEnableExternal = true;//表明开机过程中需要enable BT
}
}
在服务启动到一定阶段就会回调到 SystemService 的 onBootPhase(int) 方法，即 2 中的该方法，然后调用 BMS 中的 handleOnBootPhase() 方法。
public void handleOnBootPhase() {
......
final boolean isSafeMode = mContext.getPackageManager().isSafeMode();
if (mEnableExternal && isBluetoothPersistedStateOnBluetooth() && && !isSafeMode) {
sendEnableMsg(mQuietEnableExternal/*默认false,表示此次enable需要自动连接device/保存enable状态*/,
BluetoothProtoEnums.ENABLE_DISABLE_REASON_SYSTEM_BOOT,
mContext.getPackageName());
} else if (!isNameAndAddressSet()) {
Message getMsg = mHandler.obtainMessage(MESSAGE_GET_NAME_AND_ADDRESS);
mHandler.sendMessage(getMsg);
}
......
}
handleOnBootPhase()的内容比较单一，根据一些flag判断是否需要enable BT；而enable蓝牙这里是通过触发send msg实现。
private void sendEnableMsg(boolean quietMode, int reason, String packageName) {
//发送MESSAGE_ENABLE msg
mHandler.sendMessage(mHandler.obtainMessage(MESSAGE_ENABLE, quietMode ? 1 : 0, 0));
addActiveLog(reason, packageName, true);
mLastEnabledTime = SystemClock.elapsedRealtime();
}
case MESSAGE_ENABLE:
int quietEnable = msg.arg1;
mQuietEnable = (quietEnable == 1);//此时为false
//mBluetooth是后面绑定Bt apk中AdapterService时拿到的Binder代理对象;用以把操作bypass到BT核心框架中
if (mBluetooth == null) {
handleEnable(mQuietEnable);
} else {//如果mBluetooth不是null,说明之前已经启动过了;此时是Restart flow,以MESSAGE_RESTART_BLUETOOTH_SERVICE触发
mWaitForEnableRetry = 0;
Message enableDelayedMsg = mHandler.obtainMessage(MESSAGE_HANDLE_ENABLE_DELAYED);
mHandler.sendMessageDelayed(enableDelayedMsg, ENABLE_DISABLE_DELAY_MS);
}
break;
handleEnable() 去 Bind AdapterService 拿到它的Binder句柄。同样的在调用 BluetoothManagerService 中的 enable()、disable()等方法时，也是调到 handleEnable() 方法，从而最终调用 AdapterService 中的 enable()、disable() 方法。
private void handleEnable(boolean quietMode) {
mQuietEnable = quietMode;
try {
mBluetoothLock.writeLock().lock();
if ((mBluetooth == null) && (!mBinding)) {
//Start bind timeout and bind
Message timeoutMsg = mHandler.obtainMessage(MESSAGE_TIMEOUT_BIND);
mHandler.sendMessageDelayed(timeoutMsg, TIMEOUT_BIND_MS);
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;
}
}
} finally {
mBluetoothLock.writeLock().unlock();
}
}
然后我们看一下 doBind() 方法中的 mConnection 参数：
private BluetoothServiceConnection mConnection = new BluetoothServiceConnection();
private class BluetoothServiceConnection implements ServiceConnection {
public void onServiceConnected(ComponentName componentName, IBinder service) {
String name = componentName.getClassName();
Message msg = mHandler.obtainMessage(MESSAGE_BLUETOOTH_SERVICE_CONNECTED);
if (name.equals("com.android.bluetooth.btservice.AdapterService")) {
msg.arg1 = SERVICE_IBLUETOOTH;
} else if (name.equals("com.android.bluetooth.gatt.GattService")) {
msg.arg1 = SERVICE_IBLUETOOTHGATT;
} else {
Slog.e(TAG, "Unknown service connected: " + name);
return;
}
msg.obj = service;
mHandler.sendMessage(msg);
}
public void onServiceDisconnected(ComponentName componentName) {
// Called if we unexpectedly disconnect.
String name = componentName.getClassName();
Message msg = mHandler.obtainMessage(MESSAGE_BLUETOOTH_SERVICE_DISCONNECTED);
if (name.equals("com.android.bluetooth.btservice.AdapterService")) {
msg.arg1 = SERVICE_IBLUETOOTH;
} else if (name.equals("com.android.bluetooth.gatt.GattService")) {
msg.arg1 = SERVICE_IBLUETOOTHGATT;
} else {
Slog.e(TAG, "Unknown service disconnected: " + name);
return;
}
mHandler.sendMessage(msg);
}
}
拿到 AdapterService 服务后，发送MESSAGE_BLUETOOTH_SERVICE_CONNECTED消息且 arg1 = SERVICE_IBLUETOOTH。
case MESSAGE_BLUETOOTH_SERVICE_CONNECTED: {
IBinder service = (IBinder) msg.obj;
try {
mBluetoothLock.writeLock().lock();
mBinding = false;
mBluetoothBinder = service;
mBluetooth = IBluetooth.Stub.asInterface(Binder.allowBlocking(service));
//Register callback object
try {
mBluetooth.registerCallback(mBluetoothCallback, mContext.getAttributionSource());
} catch (RemoteException re) {
Slog.e(TAG, "Unable to register BluetoothCallback", re);
}
//Inform BluetoothAdapter instances that service is up
sendBluetoothServiceUpCallback();
//Do enable request
try {
if (!mBluetooth.enable(mQuietEnable, mContext.getAttributionSource())) {
Slog.e(TAG, "IBluetooth.enable() returned false");
}
} catch (RemoteException e) {
Slog.e(TAG, "Unable to call enable()", e);
}
} finally {
mBluetoothLock.writeLock().unlock();
}
if (!mEnable) {
waitForState(Set.of(BluetoothAdapter.STATE_ON));
handleDisable();
waitForState(Set.of(BluetoothAdapter.STATE_OFF,
BluetoothAdapter.STATE_TURNING_ON,
BluetoothAdapter.STATE_TURNING_OFF,
BluetoothAdapter.STATE_BLE_TURNING_ON,
BluetoothAdapter.STATE_BLE_ON,
BluetoothAdapter.STATE_BLE_TURNING_OFF));
}
}
主要操作：
1、拿到 bind 服务的 onBinder() 句柄，并转成 IBluetooth 类型
2、通过 IBluetooth 类型的 obj，调用 enable() 接口，将 flow 转到 AdapterService 中，做一些初始化、并向 stack 下 enable 蓝牙的 cmd
至此，enable 蓝牙的 flow 就从 BluetoothManagerService 转到 AdapterService 中了；实际上，通过 BluetoothAdapter 下来的大部分 API 调用最终都是调用到 AdapterService，再通过它下cmd 给 stack。
两个常见到的flag：
mEnable：用来标记系统运行时，蓝牙状态的变化，它有些时候跟 mEnableExternal 值一致。但如果蓝牙的状态是因为某些原因，如 stack 崩溃，导致蓝牙需要重启，重新启动时，需要靠这个 flag 来标记这种 case 的 enable/disable 状态。
mEnableExternal：它主要是记录通过用户手动操作导致的BT使能状态，如通过蓝牙功能按钮来 enable/disable 蓝牙。
到此这篇关于Android蓝牙服务启动流程分析探索的文章就介绍到这了,更多相关Android蓝牙服务启动内容请搜索脚本之家以前的文章或继续浏览下面的相关文章希望大家以后多多支持脚本之家！