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.
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:
isDownSwipeisUpSwipeisLeftSwipeisRightSwipe
That's it. Simple, easy, and quite useful.
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.
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) {
//....
}
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!
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.
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)!
- The Disco Blog
- Mobile for the masses: A gentle introduction to Android
- Mobile for the masses: Take a swipe at it! Programming gestures in Android
- Savvy Words app in Google Play
- Savvy Words app in Amazon's Appstore for Android
- View the source
- View the tests
The MIT License
Copyright (c) 2013 Andrew Glover
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