This might be a basic question but I have a situation where I've setup auto scrolling of recyclerview (Combination of Looping through data objects, view holders and applying scroll to position).
The oversight I made was about how to handle the situation when user tries to regain control over the scroll ?
The problem: How to differentiate between user trying to gain back control (with manual scrolling) vs my loop trying to scroll through ?
Solution already tried: Use custom layout manager, override calculatespeedperpixel and provide custom value. Now when the user tries to manually scroll, if the scroll speed doesn't match my custom value, we can assume it was the user who scrolled.
This was a hackish workaround and wasn't fool proof always
Set up the touch listener for the recyclerview and when it triggeres you pause scrolling and after some time trigger automatically.
Related
I just want to allow only scroll left in horizontal recyclerview for example. Please help me on that
Best way is to remove other directions item from adapter, which are getting hidden one by one. So when user scroll back ward it will not show up any thing.
I would not touch the data in your adapter (what does the data have to do with a UI business rule?). If you want, you could notify your Repository or ViewModel what views have been "scrolled" but that's a lot of events going up, and state coming down for everyone involved.
You have the tools at your disposal in the form of a combination of:
A GestureDetector (See (the documentation.)
A TouchListener (See (the documentation.)
Your favorite search engine to put these things together.
or perhaps benefit from the somewhat modular approach of RecyclerView:
Using OnItemTouchListener and a OnScrollListener to analyze the events and ignore the ones you don't want.
You could also create your own extended RecyclerView but that's more painful because you now need to change it all over the place you want this behavior.
In any case, your search engine of choice is also a good starting point. But think of this as:
You will need to intercept the touches and flings gestures (as well as other motion actions like "Dpads" and other Accessibility Events that may trigger a "scroll", evaluate in which direction this is headed, and determine if you still want that event to happen.
In our fire tv app, we are using a nested recyclerview where every vertical item have a horizontal row as a child item like playstore design.
Scrolling with dpad working fine normally but when i hold the right key for few seconds, item start scrolling very fast because it gets many events & within few second focus goes to the next random row even current row has items to scroll. So this whole problem happening in horizontal scroll(child recyclerview). I have already tried many solutions like this, this, this.
Also tried the custom layout manager, custom focus layout & other approach like slowing down the recyclerview scroll etc approach but all not working.
As far as I know, this happens at the moment when the last item is in focus, and the next item is not visible, that is, the ViewHolder has not updated the data of the first cell, so it is not clear which element to show next as if the list has ended.
You need to make sure that at least the edge of the next element is always visible on the screen.
Maybe you should play with the cell size or divider.
Edit:
The secret is to use the leanback library. It isn't lost focus!
Your gradle:
// Leanback support
def leanback_version = "1.2.0-alpha01"
implementation("androidx.leanback:leanback:$leanback_version")
Change in the layout from RecyclerView to HorizontalGridView (VerticalGridView)
Change in the Fragment import from RecyclerView.widget.GridLayoutManager to androidx.leanback.widget.GridLayoutManager
It works very fast for me and the focus no longer jumps.
Here a good article with animations but little outdated
I find listView recycles its views too fast.
When my listView scrolls, views falls off the screen gets removed right away.
Each cell(row) has image loaded using universal-image-loader.
Views which fell off the screen has to reload the image when they comes back into visible area. (it shows the stub image for short time period and loads the correct image).
I definately need to keep the view recycling behavior, but can I modify the list view's behavior so that user won't notice constant reloading of images?(maybe I keep 2-3 times of # of views in a cache than a regular list view would)
Unfortunately the code for ListView and friends is horribly complicated by the fact that it's designed to scroll unevenly-sized items without knowing the height ahead of time. That makes it brutally difficult to run with anything but the default behavior. In addition, most of the methods you'd need access to, to easily customize the behavior are hidden or private. It would be a massive job to try and roll your own (across multiple platforms, subtleties of scrolling, flinging, dragging, scrolling, keyboard focus &c).
The best solution is probably to maintain an image cache that fills in lazily around the view positions that are active. Not neccesarily easy. But way easier that trying to mess with ListView.
A very useful API for this is ListView.setRecyclerListener(AbsListView.RecyclerListener listener), which gives you a hook to track which images are actively displayed.
I can suggest you to use a ScrollView instead of the list view. The ListView is designed to display a lot of data efficiently, that's why your off screen items are destroyed. In which concerns the scroll view, once loaded, you will be able to scroll up and down without recreating the off screen objects (because they ill not be destroyed).
See: http://developer.android.com/reference/android/widget/ScrollView.html
EDIT:
If it is mandatory for you to use the listView, you cluld take a look here: How do i prevent recycled ListView items from showing old content?
There is a posibility to override the listView getView method and keep more items not to be destroyed that the number the listView is keeping.
I have a ScrollView which has two hidden images, one at the top and one at the bottom. In between there is a bunch of visible content.
What I need to do is make these images hidden by default but when you scroll all the way up or all the way down you could see them as you're scrolling. But then as soon as you stop scrolling it should bounce back to the visible area so that the hidden images aren't showing.
Basically I'm trying to imitate the bounce scrolling feature of the iphone UIScrollView.
I have my ScrollView all setup and I do a scroll at the beginning so as to hide the top hidden image. Now all I need to do is detect when a scrolling has ended, figure out the Y position, and check whether a hidden image is shown. If it is, I would just programmatically scroll the view back so that the hidden image is hidden.
I hope all that made sense.
So anyways, I know how to programmatically scroll a ScrollView. Now what I need is some sort of callback to tell me when a ScrollView ended scrolling and also a way to get the ScrollView's current 'Y' position. Are there any such methods I could use?
I looked through the ScrollView docs but nothing jumped out at me. I'm still not very familiar with the Android naming schemes so maybe I missed something obvious somewhere.
Anyways, any help would be appreciated here. Cheers.
You can use an OnTouchListener to detect when the user presses/releases the list.
You can also use the onScrollStateChanged method of the OnScrollListener class (most likely in conjunction with a touch listener) to detect changes in the SCROLL_STATE - when the list has stopped scrolling the state will change from a state that is not SCROLL_STATE_IDLE to SCROLL_STATE_IDLE.
Alternatively if you are using 2.3 or above you can use an OverScroller to get the desired effect (see Modifying Android OverScroll for how to change the over scroll effect to an iPhone like one).
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.