title: How to detect usb in android tablet which act as USB Host?
body: <p>i have tried developing a sample app with the help of the code from <a href="http://developer.android.com/guide/topics/connectivity/usb/host.html" rel="nofollow">USB Host</a>.</p>
  
  <pre><code>public class MainActivity extends Activity {
  
  UsbManager manager;
  HashMap&lt;String, UsbDevice&gt; deviceList;
  Button scanButton;
  UsbDevice device;
  
  @Override
  public void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
  
      scanButton = (Button)this.findViewById(R.id.button1);
      scanButton.setOnClickListener(new OnClickListener ()
      {
          public void onClick(View v) 
          {
              checkForDevices ();
          }
      });
  }
  
  @Override
  public void onResume ()
  {
      super.onResume();
      checkForDevices ();
  }
  
  @Override
  public boolean onCreateOptionsMenu(Menu menu) 
  {
      getMenuInflater().inflate(R.menu.activity_main, menu);
      return true;
  }
  
  protected void checkForDevices ()
  {
      manager = (UsbManager) getSystemService(Context.USB_SERVICE);
  
      deviceList = manager.getDeviceList();
      device = deviceList.get("deviceName");
      //Collection&lt;UsbDevice&gt; devices = deviceList.values();
  
     if (device != null)
         Toast.makeText(this, "Device Found", Toast.LENGTH_LONG).show();
     else
         Toast.makeText(this, "Device NOT Found", Toast.LENGTH_LONG).show();
  }
  }
  </code></pre>
  
  <p>When i run this code with a USB device connected, i get the Toast as "Device NOT Found". </p>
  
  <p>can anyone help me out to fix this?</p>
  
  <p>Thank You.</p>