USB UMS MTP設定過程

選擇MTP，PTP，UMS的選項介面就定義在UsbSettings.java，選擇其中一個選項時會執行以下代碼。

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就是去讓執行某些選項的選中與取消工作。

其中最重要的是mUsbManager.setCurrentFunction()，mUsbManger是這樣得到的：

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

它的實現在frameworks/base/core/java/android/hardware/usb/UsbManager.java。

它的介面實現在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;

這個介面就是"com.android.settings.UsbSettings" Activity。在frameworks/base/services/java/com/android/server/usb/UsbDeviceManager.java中被調用。

如果你選擇了USB調試功能，還會彈出"com.android.settings.DevelopmentSettings" Activity，也是在UsbDeviceManager.java中被調用。關於UsbDevcieManager，我們以後再細看。

如果你選擇了UMS，還會彈出"com.android.systemui.usb.UsbStorageActivity" Activity，就是“開啟USB存放裝置”的介面。它就義在定義在：
frameworks/base/packages/SystemUI/src/com/android/systemui/usb/UsbStorageActivity.java。

這些介面只有在插入USB時才會有通知顯示。在沒有插USB的情況下，有些介面是沒有入口的。我們就以UsbStorageActivity為例，介紹一下這些通知是怎麼彈出來的。

通知是怎麼彈出來的

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));

這裡註冊了監聽函數com.android.systemui.usb.StorageNotification，這個只是針對Phone，對於平板，有tablet/TabletStatusBarPolicy.java

我們來看一下註冊的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);    }

在建構函式裡就調用了onUsbMassStorageConnectionChanged函數，它最終會調到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);        }       }   

也就是說UsbStorageActivity和StorageNotification綁定在了一起，什麼時候彈出這個通知，就可以進入這個Activity了。

如果串連了USB，就會在通知欄裡顯示USB選項的通知。如果沒有串連，就會把這個通知給取消掉。那我們看一下，這個通知是怎麼彈出來的。

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會被私人成員MountServiceBinderListener用到，而MountServiceBinderListener又是繼承自IMountServiceListener.Stub，在建構函式裡被註冊。

    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);    }

所以關鍵還是在mMountService。