Fling gesture detection on grid layout
Web Technologies
Web Development
3 years ago
_x000D_
_x000D_
I want to get fling gesture detection working in my Android application.
What I have is a GridLayout that contains 9 ImageViews. 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:
Detect Gestures - Tutorial
SDK docs
Calculator Code
Nothing has worked for me so far and I was hoping for some pointers.
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manpreet
Best Answer
3 years ago
_x000D_ 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.