Android USB Host開發之manager.getDeviceList()獲取不到設備列表

同樣遇到這樣的問題，我的Android設備是原道N12C，官方的4.0.3系統，遇到這個問題，後來找了半天找到的，現在匯總一下吧：

1、創建 android.hardware.usb.host.xml，內容為：

[html] 
<permissions> 
 <feature name="android.hardware.usb.host"/> 
</permissions> 

<permissions>
 <feature name="android.hardware.usb.host"/>
</permissions>將該文件push到/system/etc/permissions目錄下

2、在/system/etc/permissions下的handheld_core_hardware.xml或者tablet_core_hardware.xml文件的<permissions>段中添加：

[html] 
<feature name="android.hardware.usb.host"> 

<feature name="android.hardware.usb.host">重啟設備

3、修改AndroidManifest.xml文件，添加以下權限：

[html]  ="android.hardware.usb.host" /> 

<uses-permission android:name="android.hardware.usb.host" />

4、枚舉設備的代碼例子：
[html] 
UsbManager manager = (UsbManager) getSystemService(Context.USB_SERVICE); 
HashMap<String, UsbDevice> deviceList = manager.getDeviceList(); 
Log.e(TAG, "get device list  = " + deviceList.size()); 
Toast.makeText(this, "get device list  = " + deviceList.size(), 200).show(); 
Iterator<UsbDevice> deviceIterator = deviceList.values().iterator(); 
while (deviceIterator.hasNext()) { 
     UsbDevice device = deviceIterator.next(); 
     Log.e(TAG, "device name = " + device.getDeviceName()); 
} 

UsbManager manager = (UsbManager) getSystemService(Context.USB_SERVICE);
HashMap<String, UsbDevice> deviceList = manager.getDeviceList();
Log.e(TAG, "get device list  = " + deviceList.size());
Toast.makeText(this, "get device list  = " + deviceList.size(), 200).show();
Iterator<UsbDevice> deviceIterator = deviceList.values().iterator();
while (deviceIterator.hasNext()) {
     UsbDevice device = deviceIterator.next();
     Log.e(TAG, "device name = " + device.getDeviceName());
}