Android4.1.2 耳机插入拔出通知流程分析

因为需要加一套新的耳机设备accessory并且展示耳机图标在状态栏，所以需要去看一下android上层的处理流程。
其实整个耳机插入的流程是：当硬件检测到耳机的插入，kernel上报UEvent到上层，上层接收到event后，调用硬件去切audio path， 硬件切换成功后，kernel发送UEvent给framework， 然后做show图标的动作。
测试过程中，使用ADB命令发送UEvent模拟耳机的插入，kernel接收uevent。

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private static final int SW_HEADPHONE_INSERT = 0x02; private static final int SW_MICROPHONE_INSERT = 0x04; private static final int SW_LINEOUT_INSERT = 0x06; 0x02&&0x04代表标准3.5mm耳机 0x06&&0x04代表accessory 使用ADB模拟耳机插入事件，如下： 第一个参数代表动作类型（path switch），第二个参数代表“键”，第四个参数代表“值”（1：插入；0：拔出。）。 Accessory 插入 sendevent /dev/input/event5 5 4 1 sendevent /dev/input/event5 5 6 1 sendevent /dev/input/event5 0 0 0 Accessory 拔出 sendevent /dev/input/event5 5 4 0 sendevent /dev/input/event5 5 6 0 sendevent /dev/input/event5 0 0 0 标准3.5耳机插入 sendevent /dev/input/event5 5 4 1 sendevent /dev/input/event5 5 2 1 sendevent /dev/input/event5 0 0 0 标准3.5耳机拔出 sendevent /dev/input/event5 5 4 0 sendevent /dev/input/event5 5 2 0 sendevent /dev/input/event5 0 0 0

1、在系统启动过程中，在SystemService中会启动很多服务，包括一个WiredAccessoryObserver。

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SystemService.java try { Slog.i(TAG, "Wired Accessory Observer"); // Listen for wired headset changes new WiredAccessoryObserver(context); } catch (Throwable e) { reportWtf("starting WiredAccessoryObserver", e); }

在WiredAccessoryObserver中，注册了开机广播，开机后，会开始所有相关的UEvent，并且开始监听。

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WiredAccessoryObserver.java //所有要监听的UEvent private static List<UEventInfo> makeObservedUEventList() { List<UEventInfo> retVal = new ArrayList<UEventInfo>(); UEventInfo uei; // Monitor h2w uei = new UEventInfo("h2w", BIT_HEADSET, BIT_HEADSET_NO_MIC); if (uei.checkSwitchExists()) { retVal.add(uei); } else { Slog.w(TAG, "This kernel does not have wired headset support"); } // Monitor USB uei = new UEventInfo("usb_audio", BIT_USB_HEADSET_ANLG, BIT_USB_HEADSET_DGTL); if (uei.checkSwitchExists()) { retVal.add(uei); } else { Slog.w(TAG, "This kernel does not have usb audio support"); } // Monitor HDMI // // If the kernel has support for the "hdmi_audio" switch, use that. It will be signalled // only when the HDMI driver has a video mode configured, and the downstream sink indicates // support for audio in its EDID. // // If the kernel does not have an "hdmi_audio" switch, just fall back on the older "hdmi" // switch instead. uei = new UEventInfo("hdmi_audio", BIT_HDMI_AUDIO, 0); if (uei.checkSwitchExists()) { retVal.add(uei); } else { uei = new UEventInfo("hdmi", BIT_HDMI_AUDIO, 0); if (uei.checkSwitchExists()) { retVal.add(uei); } else { Slog.w(TAG, "This kernel does not have HDMI audio support"); } } return retVal; }

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//开始监听 private final class BootCompletedReceiver extends BroadcastReceiver { @Override public void onReceive(Context context, Intent intent) { // At any given time accessories could be inserted // one on the board, one on the dock and one on HDMI: // observe three UEVENTs init(); // set initial status for (int i = 0; i < uEventInfo.size(); ++i) { UEventInfo uei = uEventInfo.get(i); startObserving("DEVPATH="+uei.getDevPath()); } } }

在OnEvent中，实时监听UEvent事件。

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@Override public void onUEvent(UEventObserver.UEvent event) { if (LOG) Slog.v(TAG, "Headset UEVENT: " + event.toString()); try { String devPath = event.get("DEVPATH"); String name = event.get("SWITCH_NAME"); int state = Integer.parseInt(event.get("SWITCH_STATE")); updateState(devPath, name, state); } catch (NumberFormatException e) { Slog.e(TAG, "Could not parse switch state from event " + event); } }

其中这些状态是从
root@android:/sys/class/switch # ls -l
ls -l
lrwxrwxrwx root root 2013-03-01 14:15 hdmi -> ../../devices/virtual/switch/hdmi
lrwxrwxrwx root root 2013-03-01 14:16 hdmi_audio -> ../../devices/virtual/switch/hdmi_audio
lrwxrwxrwx root root 2013-03-01 14:16 usb_audio -> ../../devices/virtual/switch/usb_audio
这些文件中读取的。
设备是定义在/devices/virtual/switch/下的。

最终会调用到AudioManager

1	mAudioManager.setWiredDeviceConnectionState(device, state, headsetName);

AudioManager的setWiredDeviceConnectionState实际是调用AudioService的setWiredDeviceConnectionState方法。

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public void setWiredDeviceConnectionState(int device, int state, String name) { synchronized (mConnectedDevices) { int delay = checkSendBecomingNoisyIntent(device, state); queueMsgUnderWakeLock(mAudioHandler, MSG_SET_WIRED_DEVICE_CONNECTION_STATE, device, state, name, delay); } }

最终会发送到上层一个广播：

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private void sendDeviceConnectionIntent(int device, int state, String name) { Intent intent = new Intent(); intent.putExtra("state", state); intent.putExtra("name", name); intent.addFlags(Intent.FLAG_RECEIVER_REGISTERED_ONLY); int connType = 0; if (device == AudioSystem.DEVICE_OUT_WIRED_HEADSET) { connType = AudioRoutesInfo.MAIN_HEADSET; intent.setAction(Intent.ACTION_HEADSET_PLUG); intent.putExtra("microphone", 1); } else if (device == AudioSystem.DEVICE_OUT_WIRED_HEADPHONE) { connType = AudioRoutesInfo.MAIN_HEADPHONES; intent.setAction(Intent.ACTION_HEADSET_PLUG); intent.putExtra("microphone", 0); } else if (device == AudioSystem.DEVICE_OUT_ANLG_DOCK_HEADSET) { connType = AudioRoutesInfo.MAIN_DOCK_SPEAKERS; intent.setAction(Intent.ACTION_ANALOG_AUDIO_DOCK_PLUG); } else if (device == AudioSystem.DEVICE_OUT_DGTL_DOCK_HEADSET) { connType = AudioRoutesInfo.MAIN_DOCK_SPEAKERS; intent.setAction(Intent.ACTION_DIGITAL_AUDIO_DOCK_PLUG); } else if (device == AudioSystem.DEVICE_OUT_AUX_DIGITAL) { connType = AudioRoutesInfo.MAIN_HDMI; intent.setAction(Intent.ACTION_HDMI_AUDIO_PLUG); } else if (device == AudioSystem.DEVICE_OUT_ANC_HEADSET) { connType = AudioRoutesInfo.MAIN_HEADSET; intent.setAction(Intent.ACTION_HEADSET_PLUG); intent.putExtra("microphone", 1); } else if (device == AudioSystem.DEVICE_OUT_ANC_HEADPHONE) { connType = AudioRoutesInfo.MAIN_HEADPHONES; intent.setAction(Intent.ACTION_HEADSET_PLUG); intent.putExtra("microphone", 0); } synchronized (mCurAudioRoutes) { if (connType != 0) { int newConn = mCurAudioRoutes.mMainType; if (state != 0) { newConn |= connType; } else { newConn &= ~connType; } if (newConn != mCurAudioRoutes.mMainType) { mCurAudioRoutes.mMainType = newConn; sendMsg(mAudioHandler, MSG_REPORT_NEW_ROUTES, SENDMSG_NOOP, 0, 0, null, 0); } } } ActivityManagerNative.broadcastStickyIntent(intent, null); } 要想在状态栏添加耳机插入的图标，在SystemUI里面添加相关逻辑。耳机拔出通知也是一样的流程。 声明：eoe文章著作权属于作者，受法律保护，转载时请务必以超链接形式附带如下信息 原文作者： cnhua5 原文地址： http://my.eoe.cn/cnhua5/archive/1252.html