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Android swipe detection made simple
Java
Latest commit b83b1aa May 13, 2013 @aglover updated readme

README.md

Gesticulate - Android swipe detection made simple

This is a simple utility that makes it easy to detect if a user is swiping a finger across a device's screen (i.e. a fling!). You can detect up, down, left, and right movements. Furthermore, you can set a distance threshold and a threshold velocity. There are reasonable default values for both thresholds as well.

Details

Gesticulate handles swipe calculations for you, but you still need to implement a listener to behave in a meaningful way. For example, you can use Android's GestureDetector type and provide it an implementation of SimpleOnGestureListener (which is also an Android class and it provides an onFling method to implement) that makes use of Gesticulate.

For example, if you want to handle a swipe down to quit an activity, you can provide a GestureDetector like so:

new GestureDetector(new SimpleOnGestureListener() {
  public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
    try {
      final SwipeDetector detector = new SwipeDetector(e1, e2, velocityX, velocityY);
        if (detector.isDownSwipe()) {
          finish();
        } else {
          return false;
        }
    } catch (Exception e) {
        // nothing
    }
    return false;
  }
});

As you can see in the code above, a SwipeDetector instance is created with onFling's parameters; once that's done, you can easily detect up, down, left, and right swipes.

The following methods are available to you:

  • isDownSwipe
  • isUpSwipe
  • isLeftSwipe
  • isRightSwipe

That's it. Simple, easy, and quite useful.

Putting it all together

To do something meaningful with a swipe, you have to first detect it; and to detect it, you'll need to attach a few listeners. For example, if you want to listen and handle swipes in a View you can do something like this:

GestureDetector gestureDetector new GestureDetector(new SimpleOnGestureListener() {
    public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
        try {
            final SwipeDetector detector = new SwipeDetector(e1, e2, velocityX, velocityY);
            if (detector.isDownSwipe()) {
                finish();
            } else {
                return false;
            }
        } catch (Exception e) {}
        return false;
    }
});

Now that you've got a GestureDetector instance, you can attach it to a View like so:

final View view = findViewById(R.id.widget33);

view.setOnClickListener(new OnClickListener() {
    public void onClick(View arg0) {}
});

view.setOnTouchListener(new View.OnTouchListener() {
    public boolean onTouch(View v, MotionEvent event) {
        return gestureDetector.onTouchEvent(event);
    }
});

Note, you'll need to provide a do-nothing OnClickListener to make things work, however, the real meat is in the OnTouchListener that ultimately makes use of the SwipeDetector inside the GestureDetector.

Further details

You can alter the details of how fast a swipe occurs as well as the length of the swipe. Simply provide these values as the last two parameters to a SwipeDetector instantiation.

public SwipeDetector(MotionEvent e1, MotionEvent e2, float velX, float velY, int minDistance, int minVelocity) {
    //....
}

Even further details

SwipeDetector is simple. If you want more details on its usage, then see the test directory. You can run the tests via ant test or you might have already noticed them run when you jar'ed it!

Installation

Clone the repo, change directories into the project's root and type ant. That'll build a .jar file you can include in your Android libs directory.

Who's using it?

Gesticulate is used by Savvy Words, which you can find in Google Play and Amazon's Appstore for Android. The Savvy Words Android app uses swipes to advance through word flash cards. It's free so download it and see Gesticulate in action (and enhance your vocabulary)!

Helpful resources

License

The MIT License

Copyright (c) 2013 Andrew Glover

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE

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