USB HOST
USB HOST:指两台手机通过OTG线连接在一起，一个主机，一个从机，主机的作用可以理解成PC端，从机可以选择USB mode
主机连接分析：
1.主要类：
UsbHostManager .java : 在host模式下管理USB状态
UsbSettingsManager.java : 通知用户
UsbDevice.java : 主要是usb设备的一些接口，基本上是获取的设备描述符
MtpNotificationManager ：Manager for MTP storage notification
UsbManager ：This is a wrapper class for the USB Manager tosupport USB accessories
2.JNI：
UsbHostManager是通过JNI由native层调用的
Native àJNIàJava
Onload.cpp -- JNI_OnLoad（）-- register_android_server_UsbHostManager()
3.USB host 连接：
com_android_server_UsbHostManager.cpp – >
static intusb_device_added(const char *devname, void* client_data) {
structusb_descriptor_header* desc;
struct usb_descriptor_iter iter;
……
jbooleanresult = env->CallBooleanMethod(thiz, method_beginUsbDeviceAdded,
deviceName,usb_device_get_vendor_id(device), usb_device_get_product_id(device),
deviceDesc->bDeviceClass,deviceDesc->bDeviceSubClass, deviceDesc->bDeviceProtocol,
manufacturerName,productName, version, serialNumber);
……
env->CallVoidMethod(thiz, method_endUsbDeviceAdded);
……
}
在usb_device_added()中会调用beginUsbDeviceAdded 和 endUsbDeviceAdded
会将连接的从机的设备信息传递给beginUsbDeviceAdded，从而使上层获取到从机设备信息，而endUsbDeviceAdded 的作用是通知用户USB 连接成功了
// beginUsbDeviceAdded方法:
UsbHostManager. Java -- >
private void beginUsbDeviceAdded() {
……
//创建UsbDevice对象
mNewDevice =new UsbDevice(deviceName, vendorID, productID,
deviceClass,deviceSubclass, deviceProtocol,
manufacturerName, productName, versionString, serialNumber);
……
}
// endUsbDeviceAdded方法：
UsbHostManager. Java -- >
private voidendUsbDeviceAdded() {
if (DEBUG) {
Slog.d(TAG,"usb:UsbHostManager.endUsbDeviceAdded()");
}
……
synchronized (mLock) {
if (mNewDevice !=null) {
mNewDevice.setConfigurations(
mNewConfigurations.toArray(newUsbConfiguration[mNewConfigurations.size()]));
mDevices.put(mNewDevice.getDeviceName(), mNewDevice);
Slog.d(TAG,"Added device " + mNewDevice);
getCurrentSettings().deviceAttached(mNewDevice);
mUsbAlsaManager.usbDeviceAdded(mNewDevice);
}
……
}
getCurrentSettings()就是UsbSettingsManager对象
UsbSettingsManager.java -- >
public voiddeviceAttached(UsbDevice device) {
finalIntent intent = createDeviceAttachedIntent(device);
//Send broadcast to running activity with registered intent
mUserContext.sendBroadcast(intent);
if(MtpNotificationManager.shouldShowNotification(mPackageManager, device)) {
// 发送Notification,这里的device就是beginUsbDeviceAdded中创建的mNewDevice对象
mMtpNotificationManager.showNotification(device);
} else {
resolveActivity(intent, device);
}
}
private static IntentcreateDeviceAttachedIntent(UsbDevice device) {
Intent intent = new Intent(UsbManager.ACTION_USB_DEVICE_ATTACHED);
intent.putExtra(UsbManager.EXTRA_DEVICE, device);
intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
return intent;
}
//应用如果想要监听USBhost状态，需要注册静态广播监听action:
UsbManager.ACTION_USB_DEVICE_ATTACHED
即：android.hardware.usb.action.USB_DEVICE_ATTACHED
4.USB host断开连接
//com_android_server_UsbHostManager.cpp – > usb_device_removed()
static int usb_device_removed(const char *devname, void* client_data) {
JNIEnv* env =AndroidRuntime::getJNIEnv();
jobject thiz =(jobject)client_data;
jstring deviceName =env->NewStringUTF(devname);
env->CallVoidMethod(thiz,method_usbDeviceRemoved, deviceName);
env->DeleteLocalRef(deviceName);
checkAndClearExceptionFromCallback(env, __FUNCTION__);
return 0;
}
// UsbHostManager.java -- > usbDeviceRemoved()
private void usbDeviceRemoved(String deviceName) {
synchronized (mLock) {
UsbDevice device =mDevices.remove(deviceName);
if (device != null) {
mUsbAlsaManager.usbDeviceRemoved(device);
getCurrentSettings().deviceDetached(device);
}
}
}
// UsbSettingsManager.java -- > deviceDetached()
public void deviceDetached(UsbDevice device) {
// clear temporary permissionsfor the device
mDevicePermissionMap.remove(device.getDeviceName());
//发送USB host断开广播
Intent intent = newIntent(UsbManager.ACTION_USB_DEVICE_DETACHED);
intent.putExtra(UsbManager.EXTRA_DEVICE, device);
if (DEBUG) Slog.d(TAG,"usbDeviceRemoved, sending " + intent);
mContext.sendBroadcastAsUser(intent, UserHandle.ALL);
//取消 USBhost通知
mMtpNotificationManager.hideNotification(device.getDeviceId());
}
//应用如果想要监听USBhost断开状态，需要注册静态广播监听action:
UsbManager. ACTION_USB_DEVICE_DETACHED
即：android.hardware.usb.action.USB_DEVICE_DETACHED