“USB连接方式”设置界面 (MTP，PTP，UMS)

“USB连接方式”设置界面

选择MTP，PTP，UMS的选项界面就定义在UsbSettings.java，选择其中一个选项时会执行以下代码。

packages/apps/Settings/src/com/android/settings/deviceinfo/UsbSettings.java

 if (preference == mMtp) {
     mUsbManager.setCurrentFunction(UsbManager.USB_FUNCTION_MTP, true);
     updateToggles(UsbManager.USB_FUNCTION_MTP);
 } else if (preference == mPtp) {
     mUsbManager.setCurrentFunction(UsbManager.USB_FUNCTION_PTP, true);
     updateToggles(UsbManager.USB_FUNCTION_PTP);
 } else if(preference == mUms) {
     mUsbManager.setCurrentFunction(UsbManager.USB_FUNCTION_MASS_STORAGE, true);
     updateToggles(UsbManager.USB_FUNCTION_MASS_STORAGE);
 }

updateToggle就是去让执行某些选项的选中与取消工作。

其中最重要的是mUsbManager.setCurrentFunction()，mUsbManger是这样得到的：

 @Override
 public void onCreate(Bundle icicle) {
     super.onCreate(icicle);
     mUsbManager = (UsbManager)getSystemService(Context.USB_SERVICE);
 }

它的实现在frameworks/base/core/java/android/hardware/usb/UsbManager.java。

它的接口实现在frameworks/base/core/java/android/hardware/usb/IUsbManager.aidl

frameworks/base/services/java/com/android/server/usb/UsbService.java

 /**
  * UsbService manages all USB related state, including both host and device support.
  * Host related events and calls are delegated to UsbHostManager, and device related
  * support is delegated to UsbDeviceManager.
  */
 public class UsbService extends IUsbManager.Stub {
     private final Context mContext;
     private UsbDeviceManager mDeviceManager;
     private UsbHostManager mHostManager;
     private final UsbSettingsManager mSettingsManager;

这个界面就是"com.android.settings.UsbSettings" Activity。在frameworks/base/services/java/com/android/server/usb/UsbDeviceManager.java中被调用。

如果你选择了USB调试功能，还会弹出"com.android.settings.DevelopmentSettings" Activity，也是在UsbDeviceManager.java中被调用。关于UsbDevcieManager，我们以后再细看。

如果你选择了UMS，还会弹出"com.android.systemui.usb.UsbStorageActivity" Activity，就是“打开USB存储设备”的界面。它就义在定义在：
frameworks/base/packages/SystemUI/src/com/android/systemui/usb/UsbStorageActivity.java。

这些界面只有在插入USB时才会有通知显示。在没有插USB的情况下，有些界面是没有入口的。我们就以UsbStorageActivity为例，介绍一下这些通知是怎么弹出来的。

通知是怎么弹出来的

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

 // storage
 mStorageManager = (StorageManager) context.getSystemService(Context.STORAGE_SERVICE);
 mStorageManager.registerListener(
         new com.android.systemui.usb.StorageNotification(context));

这里注册了监听函数com.android.systemui.usb.StorageNotification，这个只是针对Phone，对于平板，有tablet/TabletStatusBarPolicy.java

我们来看一下注册的com.android.systemui.usb.StorageNotification

frameworks/base/packages/SystemUI/src/com/android/systemui/usb/StorageNotification.java

 public class StorageNotification extends StorageEventListener {
     private static final String TAG = "StorageNotification";

     public StorageNotification(Context context) {
         mContext = context;

         mStorageManager = (StorageManager) context.getSystemService(Context.STORAGE_SERVICE);
         final boolean connected = mStorageManager.isUsbMassStorageConnected();
         Slog.d(TAG, String.format( "Startup with UMS connection %s (media state %s)", mUmsAvailable,
                 Environment.getExternalStorageState()));

         HandlerThread thr = new HandlerThread("SystemUI StorageNotification");
         thr.start();
         mAsyncEventHandler = new Handler(thr.getLooper());

         onUsbMassStorageConnectionChanged(connected);
     }

在构造函数里就调用了onUsbMassStorageConnectionChanged函数，它最终会调到updateUsbMassStorageNotification()，

 /**
  * Update the state of the USB mass storage notification
  */
 void updateUsbMassStorageNotification(boolean available) {

     if (available) {
         Intent intent = new Intent();
         intent.setClass(mContext, com.android.systemui.usb.UsbStorageActivity.class);
         intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);

         PendingIntent pi = PendingIntent.getActivity(mContext, 0, intent, 0);
         setUsbStorageNotification(
                 com.android.internal.R.string.usb_storage_notification_title,
                 com.android.internal.R.string.usb_storage_notification_message,
                 com.android.internal.R.drawable.stat_sys_data_usb,
                 false, true, pi);
     } else {
         setUsbStorageNotification(0, 0, 0, false, false, null);
     }
 }

也就是说UsbStorageActivity和StorageNotification绑定在了一起，什么时候弹出这个通知，就可以进入这个Activity了。

如果连接了USB，就会在通知栏里显示USB选项的通知。如果没有连接，就会把这个通知给取消掉。那我们看一下，这个通知是怎么弹出来的。

StorageManager

frameworks/base/core/java/android/os/storage/StorageManager.java

 public void registerListener(StorageEventListener listener) {
     if (listener == null) {
         return;
     }

     synchronized (mListeners) {
         mListeners.add(new ListenerDelegate(listener));
     }
 }

mListeners会被私有成员MountServiceBinderListener用到，而MountServiceBinderListener又是继承自IMountServiceListener.Stub，在构造函数里被注册。

 public StorageManager(Looper tgtLooper) throws RemoteException {
     mMountService = IMountService.Stub.asInterface(ServiceManager.getService("mount"));
     if (mMountService == null) {
         Log.e(TAG, "Unable to connect to mount service! - is it running yet?");
         return;
     }
     mTgtLooper = tgtLooper;
     mBinderListener = new MountServiceBinderListener();
     mMountService.registerListener(mBinderListener);
 }

所以关键还是在mMountService。