I have a Gallery based View with a negative spacing between elements, so that one zoomed out behind the previous, i.e. 'carousel'. Zooming and carousel effect is achieved by Camera transformation.
The problem arises when I try to click right side of foreground item and what I really get is click on item behind it (always to right of it)
Let me enumerate what I've already tried:
setChildrenDrawingOrderEnabled(true);
z coordinate of background item is obviously greater then foreground
one
getChildDrawingOrder was overridden as many ways as possible (and I
found out that it doesn't play any role at all - touch events don't
depend on visibility order of views)
Seems like next(right) child has greater index and therefore a priority of handling UI events, and my z-coordinate/drawing order manipulations don't change anything.
So question: how to make foreground item responsible for all click events on it?
Related
When I long-click on an item in my RecyclerView to select it (i.e., select the initial item in the selection list managed by SelectionTracker), an ActionView expands at the top of the display screen and forces all other Views downward a distance equal to the ActionView's height. This is desired behavior.
However, if the y-coordinate of the long-press is within a distance equal to the ActionView's height from the top of the item's View, then the item above that item will also be selected, which is not desirable. This is happening because, after the downward translation of all Views, the SelectionTracker sees that other item as being under the long-press coordinates and automatically determines that it, too, should be selected. This is equivalent to the user having immediately dragged the pointer up a distance equal to the ActionView's height had the ActionView not appeared.
There are two approaches I've thought of to deal with this problem:
The first involves intercepting the click and translating its y-coordinate down a distance equal to the height of the expanded ActionView, but only under the right conditions (i.e., only when there are no existing selections and only if the clicked-on item is not at position 0 in the adapter). There are several problems with this approach, but I was curious to see if it would work. (It didn't.) One class of problems centers around how to get the same coordinates that SelectionTracker uses. These are coordinates within the RecyclerView's local coordinate system (aka: "View coordinates"), but there's no way to get to them through the SelectionTracker API. They are, however, used by the ItemDetails lookup's getItemDetails(MotionEvent) method. Unfortunately, modifying the coordinates of the input MotionEvent has no "downstream" effect on the selection/non-selection of subsequent items.
The second approach was to write a custom SelectionPredicate. I believe this would work to prevent the selection of the second item, because I think the selection logic within SelectionTracker is subject to the logic within the SelectionPredicate. However, the problem I'm having with this approach is, again, getting access to the coordinates used internally by the SelectionTracker. With those coordinates, I could determine when the conditions exist that would result in the unwanted, automatic selection of that second item and, therefore, I could return false from the SelectionPredicate callbacks where appropriate.
Does anyone have a suggestion for how to address this problem?
In my application I have a custom gallery which shows some LinearLayouts (custom components to be precise, but that doesn't matter I think).
What I want is that if I scroll in between to items that it stays there and doesn't select the closest one (as it does by default).
If I override the onTouchEvent and in the case of an ACTION_UP ignore the event I get the desired result, BUT then I lose the onFling (the scrolling doesn't continue but stops immediately).
Then I think I'll have problems with my indicator of the position as I will probably lose the OnItemSelected handle, but I'm not sure of that (of course).
every suggestion is welcome.
I have a ListView in my Android application. The individual views in the list are a little bit smaller than the size of the screen.
I want the list to always show one item centered in the screen, with just a small sliver of the previous and next items showing above and below it.
When the user scrolls, I need to reposition the child view at position 0 or 1 (depending on which way they are scrolling). Currently I am doing this by calling "setSelectionFromTop" in my onScrollStateChanged method. This works, but the transition is immediate, not smooth. It is jarring and confusing in a lot of cases.
What's the best approach to fixing this? I want to animate the process of scrolling the list into the position I want, but I can't find any methods in ListView or its superclasses that let me directly control the scroll position of the entire list.
I think I could animate it using multiple calls to setSelectionFromTop(int position, int y) with progressive values of y, but I don't know how to determine the initial value of y. Is there some way to get that by interrogating the view object at the designated position?
Another challenge I have in front of me is that I want to animate the removal of an item from the list - by having it either disappear or slide away to the left, and then having the surrounding views move up and down to fill the space. Is there a straightforward and reliable way to do this with a ListView? Should I just give up on the ListView and write the whole thing as a custom view from scratch?
Thanks.
This definitely should be possible. Does smoothScrollToPosition() work?
Otherwise, you can try simulating the touches using TouchUtils.
Doubtless this is caused by my decidedly unorthodox layout - I have buttons in a LinearLayout in an Activity which is placed by an ActivityGroup into a Gallery. The ActivityGroup is also the adapter implementation and the over-all effect is full-screen sliding, snapping panels.
This is working (a treat, actually) except that a touch event on the parent layout puts all the buttons into the pressed state (and any release removes the state). A touch on an individual button is only delivered to that button.
The buttons are not receiving any events, they're only changing state.
Have I done something obviously wrong? Is this a known bug and is there a work-around?
Any insights would be very much appreciated.
As obscure as this problem is its solution may be of use to someone else, so I'll answer my own question.
As mentioned, I'm (mis)using the Gallery to provide a slidey-panel à la iPhone. I do this by returning the top level window of an Activity when the Gallery asks its Adapter implementation for a view.
Typical use of a Gallery would result in small Views to which it's desirable for the press event to be applied - it's more like a button then it is a panel. Our use means that there are many buttons in a single view and we don't want the press event to ever be applied globally.
So the work-around was very easy. I extended Gallery and deliberately broke pointToPosition(int x, int y), returning INVALID_POSITION every time. The Gallery still does everything else expected of it but skips trying to apply the touch down event to any elements but itself (to prepare itself to scroll or fling).
I hope this is of value to someone.
The views are not cached in a ViewFlipper. Is there a way wherein we can get an image of the view and show it to user so that he sees the Ui as we see on Home scrren(when we swipe the previous view also moves along and when we lift our finger, only then the next view is shown completely.)
What I want to do is that when the user starts moving his finegr on screen, the view should also move along(create an image of view).
I am not getting to do this, as when we swipe the present view goes and next view comes, we do not get both visible when we r moving our finger on screen.
Please if anyone gets what I am trying to do, do help me.
Thanks,
Farha
It's tricky to get scroll and swipe tracking working on Android, while using ViewAnimator or its subclasses.
They allow you to set in and out animations and start them at a given moment, but they work with discrete, either-this-or-the-other-view animations. They are actually using FrameLayout and after in or out animation is executed, other views' visibility is set to View.GONE to hide them from showing up under/over your current View.
The Launcher and the Gallery application are actually doing the functionality you want, by using a different approach.
They track the user touch input (onTouchEvent()), on MotionEvent.ACTION_MOVE they perform animations manually and on MotionEvent.ACTION_UP snap to the appropriate view, just like in the iPhone.
Unfortunately, this approach is actually more complicated than it looks like.
With the manual handling, you have to ensure that you are taking care of everything related to the touch input. This includes a lot of flag-raising, value-checking, event-delegating, etc.
If you want to get better acquainted with this, take a look at these classes from Gallery3D or Launcher's source code.
One other way to get nice horizontal scrolling is to use HorizontalScrollView.
You have to figure out a way to recycle your views, like you would with a ListView and you have to add the snap-to-view logic, but if you have to take care of a small number of views it could be the easiest approach.
Hope that helps.