Android ListView Not displaying the item

Showing Message Exception : null;
	@Override
	protected void onNewIntent(Intent intent) {
		try
		{
			UsbManager manager = (UsbManager) getSystemService(Context.USB_SERVICE);
			HashMap<string,> deviceList = manager.getDeviceList();
			Iterator<usbdevice> deviceIterator = deviceList.values()
					.iterator();
			while (deviceIterator.hasNext()) {
				UsbDevice device = deviceIterator.next();
				if(device==null)
					return ;
				String deviceName = device.getDeviceName();
				listDeviceName.add(deviceName);
			}

			/*runOnUiThread(new Runnable()
			{
				@Override
				public void run() {*/
					
					final ArrayAdapter<string> adapter = new ArrayAdapter<string>(this,android.R.layout.simple_list_item_1, listDeviceName);
					listview.setAdapter(adapter);
			/*	}
			});*/
		}
		catch(Exception e)
		{
			Toast.makeText(this,"Exception :"+e.getMessage(),Toast.LENGTH_SHORT).show();
		}
	}

}