As determined as I was to solve this without having to ask
for help, I am now officially confused beyond all hope.....
I've been digging, and digging, and diggin, through searches and
sample code, trying to find out how to change images (next or
previous) in an ImageView that displays one of many images at a
time with just a swipe of my finger, either to the left (next) or
right (previous). After finding a tutorial that appeared to do
close to what I was looking for, I adapted it, and came up with
the following (indentation trimmed for readability):
// NOTE: This is inside of the ImageView
private float startx = 0;
private float endx = 0;
public boolean onTouchEvent(MotionEvent event) {
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
// Remember our initial down event location.
startx = event.getRawX();
break;
case MotionEvent.ACTION_MOVE:
endx = event.getRawX();
// Handle (next)
if (endx < startx)
mCurrentPhotoIndex = (mCurrentPhotoIndex + 1)
% mPhotoIds.length;
// Handle (prev)
if (endx > startx) {
mCurrentPhotoIndex = (mCurrentPhotoIndex - 1);
if (mCurrentPhotoIndex < 0)
mCurrentPhotoIndex = mPhotoIds.length - 1;
showPhoto(mCurrentPhotoIndex);
break;
}
}
return true;
}
Obviously (well, it is NOW...), this resulted in each minute
touch of the screen advancing (or going backwards) by a seemingly
random number of images...as while I was still moving my finger
across the image, it was constantly seeing more movement, and
that triggered the MotionEvent again, and again, and again, and
again, and ... {ad nauseum}. So I started looking for a way to
tame this monster and get it under control.
After reading more, and verifying something I thought I'd seen
(ACTION_UP), I arrived at this:
// NOTE: This is inside of the ImageView
private float startx = 0;
private float endx = 0;
public boolean onTouchEvent(MotionEvent event) {
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
// Remember our initial down event location.
startx = event.getRawX();
return true; // first mod, this was still break;
case MotionEvent.ACTION_MOVE:
endx = event.getRawX();
return true; // first mod, this was still break;
// ADDED: wait for ACTION_UP, and THEN handle the event
case MotionEvent.ACTION_UP:
// Handle (next)
if (endx < startx)
mCurrentPhotoIndex = (mCurrentPhotoIndex + 1)
% mPhotoIds.length;
// Handle (prev)
if (endx > startx) {
mCurrentPhotoIndex = (mCurrentPhotoIndex - 1);
if (mCurrentPhotoIndex < 0)
mCurrentPhotoIndex = mPhotoIds.length - 1;
showPhoto(mCurrentPhotoIndex);
return true; // first mod, this was still break;
}
}
return true;
}
Note the comments saying that on the first modification, each
of the "return true;" statements in the switch statement were
still left as "break;" ... and later changed to "return true;".
It didn't change the behavior, but for the sake of completeness,
I'm including that bit of info.
Only one problem. ACTION_UP is apparently never caught. I even
put in a test that bypasses the two if statements (btw, is there
an "else" statement? how would I use it?) and advanced the image
index by 10 ... nothing happened. No change.
So at this point, while I'm not happy about not being able to
solve this on my own, I am asking for help.
Later,
--jim
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