蓝牙耳机图标显示代码路径在：

    frameworks/base/packages/SystemUI/src/com/android/systemui/statusbar/phone/

      在PhoneStatusBarPolicy.java中的函数

private final void updateBluetooth(Intent intent) {

        inticonId = R.drawable.stat_sys_data_bluetooth;

       String contentDescription = null;

       String action = intent.getAction();

        if(action.equals(BluetoothAdapter.ACTION_STATE_CHANGED)) {

           int state = intent.getIntExtra(BluetoothAdapter.EXTRA_STATE,BluetoothAdapter.ERROR);

           mBluetoothEnabled = state == BluetoothAdapter.STATE_ON;

        }else if (action.equals(BluetoothAdapter.ACTION_CONNECTION_STATE_CHANGED)) {

           int state = intent.getIntExtra(BluetoothAdapter.EXTRA_CONNECTION_STATE,

               BluetoothAdapter.STATE_DISCONNECTED);

           if (state == BluetoothAdapter.STATE_CONNECTED) {

               iconId = R.drawable.stat_sys_data_bluetooth_connected;

               contentDescription = mContext.getString(R.string.accessibility_bluetooth_connected);

            }else {

               contentDescription = mContext.getString(

                       R.string.accessibility_bluetooth_disconnected);

            }

        }else {

           return;

        }

 

        mService.setIcon("bluetooth",iconId, 0, contentDescription);

       mService.setIconVisibility("bluetooth", mBluetoothEnabled);

    }

通过 updateBluetooth这个函数可以看到，蓝牙耳机的图标是根据广播 ACTION_CONNECTION_STATE_CHANGED来判断的。

下面我们来看一看广播ACTION_CONNECTION_STATE_CHANGED是如何发送的，

代码路径在：

packages/apps/Bluetooth/src/com/android/bluetooth/btservice

在AdapterProperties.java中的函数

void sendConnectionStateChange(BluetoothDevicedevice, int profile, int state, int prevState) {

       ......

       synchronized (mObject) {

            updateProfileConnectionState(profile,state, prevState);

           if (updateCountersAndCheckForConnectionStateChange(state, prevState)) {

               setConnectionState(state);

               Intent intent = new Intent(BluetoothAdapter.ACTION_CONNECTION_STATE_CHANGED);

               intent.putExtra(BluetoothDevice.EXTRA_DEVICE, device);

               intent.putExtra(BluetoothAdapter.EXTRA_CONNECTION_STATE,

                       convertToAdapterState(state));

           intent.putExtra(BluetoothAdapter.EXTRA_PREVIOUS_CONNECTION_STATE,

                       convertToAdapterState(prevState));

               ......

            }

        }

    }

通过函数 sendConnectionStateChange来看广播的发送是由 updateCountersAndCheckForConnectionStateChange()函数的返回值决定的。

private booleanupdateCountersAndCheckForConnectionStateChange(int state, int prevState) {

       switch (prevState) {

           case BluetoothProfile.STATE_CONNECTING:

               mProfilesConnecting--;

               break;

           case BluetoothProfile.STATE_CONNECTED:

               mProfilesConnected--;

               break;

           case BluetoothProfile.STATE_DISCONNECTING:

               mProfilesDisconnecting--;

               break;

        }

       switch (state) {

            case BluetoothProfile.STATE_CONNECTING:

               mProfilesConnecting++;

               return (mProfilesConnected == 0 && mProfilesConnecting == 1);

           case BluetoothProfile.STATE_CONNECTED:

               mProfilesConnected++;

               return (mProfilesConnected == 1);

           case BluetoothProfile.STATE_DISCONNECTING:

               mProfilesDisconnecting++;

               return (mProfilesConnected == 0 && mProfilesDisconnecting == 1);

           case BluetoothProfile.STATE_DISCONNECTED:

               return (mProfilesConnected == 0 && mProfilesConnecting == 0);

           default:

               return true;

        }

    }

通过updateCountersAndCheckForConnectionStateChange来看，mProfilesConnecting、mProfilesConnected、mProfilesDisconnecting这三个变量满足一定的条件函数返回才为TRUE。而这三个变量会根据连蓝耳机上次状态和当前状态的进行加减。

蓝牙耳机图标显示过程：

    蓝牙耳机的连接分为Headset Profile 和A2DP Profile两个Profile，连接的时候只要有一个连接上就会返回TRUE，发送广播，从而显示蓝牙耳机图标，而断开连接的时候只有两个都断开了才会返回TRUE，发送广播，显示蓝牙普通图标。