Android 耳机插拔流程源码跟踪浅析

Android 开发过程中，使用耳机控制拍照，控制音乐播放，控制打电话等，线控再到蓝牙控... 耳机也在不断升级，耳机插拔的程序这一块也在不断完善。因此，在定制开发过程中，阅读这部分流程代码是必修的功课了，至少首先的要搞清楚程序走的线路流程。下面结合我在实际工作过程中遇到的bug，需求定制等做个简单的总结。

第一节，插拔耳机时，事件上报

抓取事件命令：

• 查看有哪些事件可以get

  PS C:\Users\xxxx> adb shell getevent -l
  add device 1: /dev/input/event11
  name:     "comp"
  add device 2: /dev/input/event10
  name:     "accel"
  add device 3: /dev/input/event9
  name:     "gyro"
  add device 4: /dev/input/event0
  name:     "Power Button"
  add device 5: /dev/input/event5
  name:     "Video Bus"
  add device 6: /dev/input/event8
  name:     "baytrailaudio Intel MID Audio Jack"
  add device 7: /dev/input/event6
  name:     "gpio-lesskey"
  add device 8: /dev/input/event7
  name:     "dollar_cove_power_button"
  add device 9: /dev/input/event3
  name:     "jsa1212_als"
  add device 10: /dev/input/event2
  name:     "jsa1212_ps"
  add device 11: /dev/input/event1
  name:     "sx9500"
  add device 12: /dev/input/event4
  name:     "goodix_ts"

• event8正式我们想要查看的event。

  add device 6: /dev/input/event8 
  name:     "baytrailaudio Intel MID Audio Jack"

  下面我们开始get event8 详细信息，下面事件信息分别是拔出和插入耳机时事件信息。SW_MICROPHONE_INSERT带mic的耳机。

  PS C:\Users\xxxx> adb shell getevent -l  /dev/input/event8
  EV_SW        SW_HEADPHONE_INSERT  00000000
  EV_SW        SW_MICROPHONE_INSERT 00000000
  EV_SYN       SYN_REPORT           00000000
  EV_SW        SW_HEADPHONE_INSERT  00000001
  EV_SW        SW_MICROPHONE_INSERT 00000001
  EV_SYN       SYN_REPORT           00000000

  从上面的输出数据中我们可以看到，插入耳机上报1，拔出是0。
  另外，我们可以从get parameter命令看到当前信息(注：这个命令是特别方案才有，取决于芯片商)

PS C:\Users\xxxx> adb shell parameter status
...
Last Applied [Pending] Configurations:
======================================
OutputDevice.Private.Selected: WiredSpeakers [<none>]
IHF.SDRC: Enabled [<none>]
InputDevice.Selected: HeadsetMic [<none>]
OutputDevice.Selected: Multimedia.IHF.Headset [<none>]
IHF.StereoEq: Enabled [<none>]
Headset.Selected: Digital [<none>]
Voip.Tuning: Default [<none>]
Calibration: Default [<none>]
LPE_Mixer: Default [<none>]
Audio.voice: Default [<none>]
...

InputDevice.Selected ，OutputDevice.Selected等我们可以看到是使用耳机状态。拔掉耳机，我们看一下具体的parameter信息：

Last Applied [Pending] Configurations:
======================================
OutputDevice.Private.Selected: WiredSpeakers [<none>]
IHF.SDRC: Enabled [<none>]
InputDevice.Selected: VoiceRecgnition.FrontMic [<none>]
OutputDevice.Selected: Multimedia.IHF [<none>]
IHF.StereoEq: Enabled [<none>]
Headset.Selected: Digital [<none>]
Voip.Tuning: Default [<none>]
Calibration: Default [<none>]
LPE_Mixer: Default [<none>]

此时相关参数发生了变化：InputDevice.Selected，OutputDevice.Selected 等已经发生了变化。

第二节，插入拔出framework部分相关源码流程分析

涉及到的类文件

• InputManagerService.java
  ./framework/base/services/core/java/com/android/server/input/InputManagerService.java
  *WiredAccessoryManager.java.
  ./framework/base/services/core/java/com/android/server/WiredAccessoryManager.java
• config.xml
  ./framework/base/core/res/res/values/config.xml
• SystemServer.java
  ./framework/base/services/java/com/android/server/SystemServer.java
• AudioManager.java
  ./base/media/java/android/media/AudioManager.java
• AudioService.java
  ./base/media/java/android/media/AudioService.java

UEvent和InputEvent的选择
这两个的切换主要是通过设置属性来的。该属性开关位于config.xml中：

    <!-- When true use the linux /dev/input/event subsystem to detect the switch changes
         on the headphone/microphone jack. When false use the older uevent framework. -->
    <bool name="config_useDevInputEventForAudioJack">false</bool>

从注释里面我们可以看到设置为true，选择/dev/input/event ，设置为false 选择uevent 来控制事件的上报。

在InputManagerService.java 构造方法中，config_useDevInputEventForAudioJack的值初始化mUseDevInputEventForAudioJack 决定采用哪种方式。

    public InputManagerService(Context context) {
this.mContext = context;
this.mHandler = new InputManagerHandler(DisplayThread.get().getLooper());

//config_useDevInputEventForAudioJack 
        mUseDevInputEventForAudioJack =
                context.getResources().getBoolean(R.bool.config_useDevInputEventForAudioJack);
        Slog.i(TAG, "Initializing input manager, mUseDevInputEventForAudioJack="
                + mUseDevInputEventForAudioJack);
        mPtr = nativeInit(this, mContext, mHandler.getLooper().getQueue());

        LocalServices.addService(InputManagerInternal.class, new LocalService());
    }

插入耳机底层kernal事件上报后(注:这段过程需要研究)，转到InputManagerService.java中的notifySwitch方法中。
接下来我们先看notifySwitch方法：

    // Native callback. 
private void notifySwitch(long whenNanos, int switchValues, int switchMask) {

        ... 因为当前我们只看耳机插拔的模式，因此，其他的先排除。
if (mUseDevInputEventForAudioJack && (switchMask & SW_JACK_BITS) != 0) {
            mWiredAccessoryCallbacks.notifyWiredAccessoryChanged(whenNanos, switchValues,
                    switchMask);
        }
    }

接下来是走到mWiredAccessoryCallbacks 回调中。
有个疑问：mWiredAccessoryCallbacks是什么呢？ 先看看回调*
接下来我们先顺藤摸瓜从这个callBack的声明初始化开始，找到目标。
WiredAccessoryCallbacks接口的声明，它在WiredAccessoryManager.java类的内部，接口有两个方法，一个是notifyWiredAccessoryChanged另外一个是systemReady 。

    /**
 * Callback interface implemented by WiredAccessoryObserver.
 */
public interface WiredAccessoryCallbacks {
public void notifyWiredAccessoryChanged(long whenNanos, int switchValues, int switchMask);
public void systemReady();
    }

再看何时将它初始化：

    public void setWindowManagerCallbacks(WindowManagerCallbacks callbacks) {
        mWindowManagerCallbacks = callbacks;
    }

setWindowManagerCallbacks的调用在SystemServer.java中，也就是InputManagerService被创建的时候。
接下来转到SystemServer.java中：

            inputManager = new InputManagerService(context);
            wm = WindowManagerService.main(context, inputManager,
                    mFactoryTestMode != FactoryTest.FACTORY_TEST_LOW_LEVEL/* always false*/,
                    !mFirstBoot/* always true*/,mOnlyCore/* always false*/);
            ServiceManager.addService(Context.WINDOW_SERVICE, wm);
//register the inputManagerService to ServiceManager
            ServiceManager.addService(Context.INPUT_SERVICE, inputManager); 
...
if (!disableMedia) {
try {
                    Slog.i(TAG, "Wired Accessory Manager");
// Listen for wired headset changes
                    inputManager.setWiredAccessoryCallbacks(
new WiredAccessoryManager(context, inputManager));
                } catch (Throwable e) {
                    reportWtf("starting WiredAccessoryManager", e);
                }
            }

从上面的代码可以看到WiredAccessoryManager对象直接被注册为callBack 因此，mWiredAccessoryCallbacks.notifyWiredAccessoryChanged直接将后面的任务交给了WiredAccessoryManager类。

WiredAccessoryManager.java
notifyWiredAccessoryChanged方法：

        @Override
public void notifyWiredAccessoryChanged(long whenNanos, int switchValues, int switchMask) {
synchronized (mLock) {
int headset;
            mSwitchValues = (mSwitchValues & ~switchMask) | switchValues;
switch (mSwitchValues &
                (SW_HEADPHONE_INSERT_BIT | SW_MICROPHONE_INSERT_BIT | SW_LINEOUT_INSERT_BIT)) {
case 0:
                    headset = 0;
break;

case SW_HEADPHONE_INSERT_BIT:
                    headset = BIT_HEADSET_NO_MIC;
break;

case SW_LINEOUT_INSERT_BIT:
                    headset = BIT_LINEOUT;
break;

case SW_HEADPHONE_INSERT_BIT | SW_MICROPHONE_INSERT_BIT:
                    headset = BIT_HEADSET;
break;

case SW_MICROPHONE_INSERT_BIT:
                    headset = BIT_HEADSET;
break;

default:
                    headset = 0;
break;
            }
//上面的switch 语句是看哪种耳机，带mic否？
            updateLocked(NAME_H2W,
                (mHeadsetState & ~(BIT_HEADSET | BIT_HEADSET_NO_MIC | BIT_LINEOUT)) | headset);
        }
    }

接着转到updateLocked方法,该方法作用是check当前模式是否变化。也就是是否发生耳机拔出了或者插入了(0->1;1->0的变化)。state无变化则不会继续处理。
疑问：这里的BIT_USB_HEADSET_ANLG和BIT_USB_HEADSET_DGTL是什么?

    /**
 * Compare the existing headset state with the new state and pass along accordingly. Note
 * that this only supports a single headset at a time. Inserting both a usb and jacked headset
 * results in support for the last one plugged in. Similarly, unplugging either is seen as
 * unplugging all.
 *
 * @param newName One of the NAME_xxx variables defined above.
 * @param newState 0 or one of the BIT_xxx variables defined above.
 */
private void updateLocked(String newName, int newState) {
// Retain only relevant bits
int headsetState = newState & SUPPORTED_HEADSETS;
int usb_headset_anlg = headsetState & BIT_USB_HEADSET_ANLG;
int usb_headset_dgtl = headsetState & BIT_USB_HEADSET_DGTL;
int h2w_headset = headsetState & (BIT_HEADSET | BIT_HEADSET_NO_MIC | BIT_LINEOUT);
boolean h2wStateChange = true;
boolean usbStateChange = true;

//fulairy add: check the state changed or not mHeadsetState is old state and headsetState is new state
if (mHeadsetState == headsetState) {
            Log.e(TAG, "No state change.");
return;
        }

// reject all suspect transitions: only accept state changes from:
// - a: 0 headset to 1 headset
// - b: 1 headset to 0 headset
if (h2w_headset == (BIT_HEADSET | BIT_HEADSET_NO_MIC | BIT_LINEOUT)) {
            Log.e(TAG, "Invalid combination, unsetting h2w flag");
            h2wStateChange = false;
        }
// - c: 0 usb headset to 1 usb headset
// - d: 1 usb headset to 0 usb headset
if (usb_headset_anlg == BIT_USB_HEADSET_ANLG && usb_headset_dgtl == BIT_USB_HEADSET_DGTL) {
            Log.e(TAG, "Invalid combination, unsetting usb flag");
            usbStateChange = false;
        }
//flairy add : h2wStateChange and usbStateChange all not changed .
if (!h2wStateChange && !usbStateChange) {
            Log.e(TAG, "invalid transition, returning ...");
return;
        }

        mWakeLock.acquire(); 
//flairy add : yeah ,you changed pls mHandler deal with it .
        Message msg = mHandler.obtainMessage(MSG_NEW_DEVICE_STATE/*what*/, headsetState/*arg0*/, //headsetState 新状态
                mHeadsetState/*arg1*/, newName/*obj*/);//mHeadsetState 旧的状态,newName name of the headset .
        mHandler.sendMessage(msg);

        mHeadsetState = headsetState;// update the status .
    }

接下来mHandler处理：

    private final Handler mHandler = new Handler(Looper.myLooper(), null, true) {
@Override
public void handleMessage(Message msg) {
switch (msg.what) {
case MSG_NEW_DEVICE_STATE:
                    setDevicesState(msg.arg1, msg.arg2, (String)msg.obj);
                    mWakeLock.release();
break;
                ...
            }
        }
    };

//这个方法挺有意思...就是没看明白 :(
private void setDevicesState(
int headsetState, int prevHeadsetState, String headsetName) {
synchronized (mLock) {
int allHeadsets = SUPPORTED_HEADSETS;
for (int curHeadset = 1; allHeadsets != 0; curHeadset <<= 1) {
if ((curHeadset & allHeadsets) != 0) {
                    setDeviceStateLocked(curHeadset, headsetState, prevHeadsetState, headsetName);
                    allHeadsets &= ~curHeadset;
                }
            }
        }
    }

private void setDeviceStateLocked(int headset,
int headsetState, int prevHeadsetState, String headsetName) {
if ((headsetState & headset) != (prevHeadsetState & headset)) {
int outDevice = 0;
int inDevice = 0;
int state;
//important: state set start 
if ((headsetState & headset) != 0) {
                state = 1;
            } else {
                state = 0;
            }
// important : state set end 

if (headset == BIT_HEADSET) {
                outDevice = AudioManager.DEVICE_OUT_WIRED_HEADSET;
                inDevice = AudioManager.DEVICE_IN_WIRED_HEADSET;
            } else if (headset == BIT_HEADSET_NO_MIC){
                outDevice = AudioManager.DEVICE_OUT_WIRED_HEADPHONE;
            } else if (headset == BIT_LINEOUT){
                outDevice = AudioManager.DEVICE_OUT_LINE;
            } else if (headset == BIT_USB_HEADSET_ANLG) {
                outDevice = AudioManager.DEVICE_OUT_ANLG_DOCK_HEADSET;
            } else if (headset == BIT_USB_HEADSET_DGTL) {
                outDevice = AudioManager.DEVICE_OUT_DGTL_DOCK_HEADSET;
            } else if (headset == BIT_HDMI_AUDIO) {
                outDevice = AudioManager.DEVICE_OUT_HDMI;
            } else {
                Slog.e(TAG, "setDeviceState() invalid headset type: "+headset);
return;
            }
...

//update the out device and in device .
if (outDevice != 0) {
              mAudioManager.setWiredDeviceConnectionState(outDevice, state, headsetName);
            }
//这里我们仅仅看in device. 
if (inDevice != 0) {
              mAudioManager.setWiredDeviceConnectionState(inDevice, state, headsetName);
            }
        }
    }

接下来的流程就交给了AudioManager，从代码看实际上真正的处理这是AudioService

IAudioService service = getService();
...
service.setWiredDeviceConnectionState(device, state, name);

因此我们跳过AudioManager.java直接从AduioService.java看。

setWiredDeviceConnectionState--> queueMsgUnderWakeLock-->sendMsg--> ...  
从源代码看到这里，你可以发现AudioService是个非常重要的角色，因此它里面的控制逻辑很多建议多多理解。

接下来我们直接从handler处理消息开始。因为我们只搞清楚headset处理的这条线。

                ...
case MSG_SET_WIRED_DEVICE_CONNECTION_STATE:
                    onSetWiredDeviceConnectionState(msg.arg1, msg.arg2, (String)msg.obj);
                    mAudioEventWakeLock.release();
break;
...

private void onSetWiredDeviceConnectionState(int device, int state, String name)
{
synchronized (mConnectedDevices) {
//state==0 ===> the device is disconnected.
            ...  //ignore BluetoothA2dp Device.
            ...
            handleDeviceConnection((state == 1)/*FULAIRY ADD :true if connected , false if disconnected */, device, (isUsb ? name : ""/* FuLaiRy add :that's why we get empty string when we use common headset.*/));
            ... // other conditions we also ignore 
// FuLAIRY ADD :Send broadcast ...
if (!isUsb && (device != AudioSystem.DEVICE_IN_WIRED_HEADSET)) {
                sendDeviceConnectionIntent(device, state, name);
            }
        }
    }

onSetWiredDeviceConnectionState方法中我们忽略其他一些情况的处理，看最主要的两个： 一个是handleDeviceConnection,另外一个是sendDeviceConnectionIntent。因此，下面我们主要看着两个方法。

• handleDeviceConnection

    private boolean handleDeviceConnection(boolean connected, int device, String params) {
        synchronized (mConnectedDevices) {
  //Fulairy: mConnectedDevices is a hashMap :
  //private final HashMap <Integer, String> mConnectedDevices = new HashMap <Integer, String>();
  
  // the if means that if key and values are all equal,indicate the same device has been connected .
  boolean isConnected = (mConnectedDevices.containsKey(device) &&
                    (params.isEmpty() || mConnectedDevices.get(device).equals(params)));
  
  if (isConnected && !connected) {
  //断开
                AudioSystem.setDeviceConnectionState(device,
                                              AudioSystem.DEVICE_STATE_UNAVAILABLE,
                                              mConnectedDevices.get(device));
                 mConnectedDevices.remove(device);
  return true;
            } else if (!isConnected && connected) {
  //连接
  //接下来的处理在JNI方法
                 AudioSystem.setDeviceConnectionState(device,
                                                      AudioSystem.DEVICE_STATE_AVAILABLE,
  params);
                 mConnectedDevices.put(new Integer(device), params);
  return true;
            }
        }
  return false;
    }
  ...

  JNI部分放到后面补充。

• sendDeviceConnectionIntent
  从这个方法，可以看到intent耳机插拔的广播我们可以在app层通过监听ACTION_HEADSET_PLUG。 intent携带了，当前最新状态state ,name以及microphone(耳机是否带麦)。可以从自带音乐播放器看看。

  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 ||
                   device == AudioSystem.DEVICE_OUT_LINE) {
  /*do apps care about line-out vs headphones?*/
            connType = AudioRoutesInfo.MAIN_HEADPHONES;
            intent.setAction(Intent.ACTION_HEADSET_PLUG);
            intent.putExtra("microphone", 0);
        } ...
        ... 割舍了也很重要的一些其他逻辑处理。
  try {
            ActivityManagerNative.broadcastStickyIntent(intent, null, UserHandle.USER_ALL); // 后面的流程就不继续跟了，这个是通用，单独分出一条线比较好，check里面是如何运作的。
        } finally ...
    }

  说到这里我们不得不提一下，插入与拔出耳机通知栏耳机图标的显示与消失。

  第三节，插拔耳机，通知栏图标的显示与消失。

  在原生应用中，搜索ACTION_HEADSET_PLUG我们是搜索不到的。因为没有做处理。下面我们自己添加。
  涉及到的文件

• PhoneStatusBarPolicy.java
  frameworks/base/packages/SystemUI/src/com/android/systemui/statusbar/phone

添加广播注册

        //FuLairy add: HeadSet start
        filter.addAction(Intent.ACTION_HEADSET_PLUG) ;
//FuLairy add: HeadSet start
        mContext.registerReceiver(mIntentReceiver, filter, null, mHandler);

// FuLaiRy add Headset start
        mService.setIcon(SLOT_HEADSET,  R.drawable.stat_sys_tty_mode, 0, null);
        mService.setIconVisibility(SLOT_HEADSET, false);
// FuLaiRy add Headset end

新增update方法

    //FuLairy add: HeadSet start

public final void updateHeadSet(intent){

final int state = intent.getIntExtra("state",0/*default*/) ;
final String name = intent.getStringExtra("name",""/*this always be empty string*/) ;
final int microPhone =intent.getIntExtra("microphone",0/*default*/) ;

switch(state){

case 0:
//disconnected
            String contentDescription = mContext.getString(R.string.headset_disconnected);
            mService.setIcon(SLOT_HEADSET, R.drawable.head_set_disconnected_icon, 0, contentDescription);
            mService.setIconVisibility(SLOT_HEADSET, false);
break;
case 1:
//connected
                String contentDescription = mContext.getString(R.string.headset_connected);
if(microPhone==1){

                    mService.setIcon(SLOT_HEADSET, R.drawable.head_set_connected_icon_microphone, 0, contentDescription);
                    mService.setIconVisibility(SLOT_HEADSET, true);
                }else if(microPhone==0){

                    mService.setIcon(SLOT_HEADSET, R.drawable.head_set_connected_icon_nomicrophone, 0, contentDescription);
                    mService.setIconVisibility(SLOT_HEADSET, true);
                }
break;
default:
                    mService.setIconVisibility(SLOT_HEADSET, false);
    }}//FuLairy add: HeadSet end

core/res/res/values/config.xml中添加：
<item><xliff:g id="id">headset</xliff:g></item>

大概就这个思路，由于条件限制了，不然可以完整提供一下patch。流程清楚后，修改就快的多。