I want to get fling
gesture detection working in my Android application.
What I have is a GridLayout
that contains 9 ImageView
s. The source can be found here: Romain Guys's Grid Layout.
That file I take is from Romain Guy's Photostream application and has only been slightly adapted.
For the simple click situation I need only set the onClickListener
for each ImageView
I add to be the main activity
which implements View.OnClickListener
. It seems infinitely more complicated to implement something that recognizes a fling
. I presume this is because it may span views
?
If my activity implements
OnGestureListener
I don't know how to
set that as the gesture listener for
the Grid
or the Image
views that I
add.
public class SelectFilterActivity extends Activity implements
View.OnClickListener, OnGestureListener { ...
If my activity implements
OnTouchListener
then I have no
onFling
method to override
(it has
two events as parameters allowing me
to determine if the fling was
noteworthy).
public class SelectFilterActivity extends Activity implements
View.OnClickListener, OnTouchListener { ...
If I make a custom View
, like GestureImageView
that extends ImageView
I don't know how to tell the activity that a fling
has occurred from the view. In any case, I tried this and the methods weren't called when I touched the screen.
I really just need a concrete example of this working across views. What, when and how should I attach this listener
? I need to be able to detect single clicks also.
// Gesture detection
mGestureDetector = new GestureDetector(this, new GestureDetector.SimpleOnGestureListener() {
public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
int dx = (int) (e2.getX() - e1.getX());
// don't accept the fling if it's too short
// as it may conflict with a button push
if (Math.abs(dx) > MAJOR_MOVE && Math.abs(velocityX) > Math.absvelocityY)) {
if (velocityX > 0) {
moveRight();
} else {
moveLeft();
}
return true;
} else {
return false;
}
}
});
Is it possible to lay a transparent view over the top of my screen to capture flings?
If I choose not to inflate
my child image views from XML can I pass the GestureDetector
as a constructor parameter to a new subclass of ImageView
that I create?
This is the very simple activity that I'm trying to get the fling
detection to work for: SelectFilterActivity (Adapted from photostream).
I've been looking at these sources:
Nothing has worked for me so far and I was hoping for some pointers.
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.