Android – Detection of plugged in USB device

androidlinuxlinux-device-driverlinux-kernelusb

I'd like to know, which part of the system is responsible for detection of plugged-in device in the USB port

It may be a USB host port, so that a plugged-in device will be considered a USB client (so port owner is host),
or it may be a USB client port, so that a plugged-in device will be considered a USB host (so port owner is client)

What I am interested in is a moment WHEN the system actually detects (by change of resistance maybe) that something has been plugged in, and based on from which port the signal is coming (host port or client port), either host port driver or client port driver is deployed
I want to know, HOW system picks up this or that driver, based on that "plugged-in" event

Where should I look for that ? In USB core maybe ?

Best Answer

I understand what you are asking, and rightly when a usb device is connected then the current fluctuation (across resistors) leads to notification. Then the host (there can be negotiation that who will be host in OTG mode but that also happens after enumeration process).

Enumeration is main process which is most important. USB follows star tier topology and whole system is based on same.

NOTE: It is very important to note that all the transactions of packets are initiated by host. The client is at mercy of host. This is very important in understanding the usb system.

Pls refer: http://www.beyondlogic.org/usbnutshell/usb1.shtml

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Android – Fling gesture detection on grid layout

Thanks to Code Shogun, whose code I adapted to my situation.

Let your activity implementOnClickListener as usual:

public class SelectFilterActivity extends Activity implements OnClickListener {

  private static final int SWIPE_MIN_DISTANCE = 120;
  private static final int SWIPE_MAX_OFF_PATH = 250;
  private static final int SWIPE_THRESHOLD_VELOCITY = 200;
  private GestureDetector gestureDetector;
  View.OnTouchListener gestureListener;

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    /* ... */

    // Gesture detection
    gestureDetector = new GestureDetector(this, new MyGestureDetector());
    gestureListener = new View.OnTouchListener() {
      public boolean onTouch(View v, MotionEvent event) {
        return gestureDetector.onTouchEvent(event);
      }
    };

  }

  class MyGestureDetector extends SimpleOnGestureListener {
    @Override
    public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
      try {
        if (Math.abs(e1.getY() - e2.getY()) > SWIPE_MAX_OFF_PATH)
          return false;
        // right to left swipe
        if(e1.getX() - e2.getX() > SWIPE_MIN_DISTANCE && Math.abs(velocityX) > SWIPE_THRESHOLD_VELOCITY) {
          Toast.makeText(SelectFilterActivity.this, "Left Swipe", Toast.LENGTH_SHORT).show();
        } else if (e2.getX() - e1.getX() > SWIPE_MIN_DISTANCE && Math.abs(velocityX) > SWIPE_THRESHOLD_VELOCITY) {
          Toast.makeText(SelectFilterActivity.this, "Right Swipe", Toast.LENGTH_SHORT).show();
        }
      } catch (Exception e) {
         // nothing
      }
      return false;
    }

    @Override
    public boolean onDown(MotionEvent e) {
      return true;
    }
  }
}

Attach your gesture listener to all the views you add to the main layout;

// Do this for each view added to the grid
imageView.setOnClickListener(SelectFilterActivity.this); 
imageView.setOnTouchListener(gestureListener);

Watch in awe as your overridden methods are hit, both the onClick(View v) of the activity and the onFling of the gesture listener.

public void onClick(View v) {
  Filter f = (Filter) v.getTag();
  FilterFullscreenActivity.show(this, input, f);
}

The post 'fling' dance is optional but encouraged.

Android – unique Android device ID

Settings.Secure#ANDROID_ID returns the Android ID as an unique for each user 64-bit hex string.

import android.provider.Settings.Secure;

private String android_id = Secure.getString(getContext().getContentResolver(),
                                                        Secure.ANDROID_ID);

Also read Best practices for unique identifiers: https://developer.android.com/training/articles/user-data-ids

Best Answer

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Android – Fling gesture detection on grid layout

Android – unique Android device ID

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