When my activity launches, it should launch with a specific item snapped to center. SnapHelper helper new LinearSnapHelper () helper.attachToRecyclerView (recyclerView) Now, I have two scenarios where I would want an item to come to center. Scrolling in Android: Custom Scroll Behavior for a List of Varying HeightĪ scrollbar is a useful and recognizable way to show progress and position in a feed of content. For the adapter items to snap at the center, I've attached a LinearSnapHelper to the recyclerview. It’s an important feature for a news publication to have, especially since articles have items varying in height, from one-line bylines to vertically-oriented images.Īs an Android developer on The Wall Street Journal, handling lists with content of varying heights is a common use case on Android. Unfortunately, a scrollbar that doesn’t behave erratically is not well supported out of the box when working with dynamically-sized items in a RecyclerView. The scrollbar will not move smoothly – it will jump around and resize. To keep things performant, we want a scrollbar that can accurately and smoothly track the user’s position in a list of content without knowing the entire list. Holds information about a smooth scroll request by a RecyclerView. To accomplish this for a list of items with varying height, you must either create a custom layoutManager that estimates how the scrollbar should move for each user interaction, or that measures the entire list to calculate the size of each item before displaying it. Each CardView has a Button at the bottom of the layout, which when pressed prompts the call: recyclerView.smoothScrollBy(x, y) This scrolls horizontally to the next card as expected, unless the user touches the screen as it is scrolling. We chose the first approach - its performance will always be better and can support updates to the content without remeasuring everything.īefore we can go deeper, let’s discuss the nomenclature for the various parts that make up a scrollbar.Įven with items only varying in height a small amount, the scrollbar thumb can be jarring. I am using an Adapter to fill a RecyclerView with numerous CardView layouts (horizontally). To adjust how the scrollbar behaves for every increment of scroll for the solution we pursued, we have to use a custom LayoutManager. The LayoutManager is responsible for positioning items as well as recycling items in a RecyclerView. There are several stock layout managers, but we are interested in the LinearLayoutManager. We want smoothScrolling off so we can can add that to our LayoutManager’s constructor. #Smoothscroll vs scroll android androidĬlass CoolLayoutManager extends LinearLayoutManager return (SMOOTH_VALUE * firstPos) + heightOfScreen Ībove this code block, we must check if we are at the last item – if so, scroll to the end.Refer to the sample for an example, if you don't know how to do it. Create your implementation of RecyclerView.Adapter.Add DiscreteScrollView to your layout either using xml or code: Best Java code snippets using 7. (Showing top 20 results out of 1,170) MainActivit圓.run().One thing to note - you should NOT set LayoutManager. It is also built to allow for very easy adaptation to support custom views. The library provides an iOS-like over-scrolling effect applicable over almost all Android native scrollable views. If you have ever used RecyclerView - you already know how to use this library. Over-Scroll Support For Android's RecyclerView, ListView, GridView, ScrollView. All public API is accessible through DiscreteScrollView class, which is a simple descendant of RecyclerView. Scrolling is a major interaction performed almost in every application around. void, startSmoothScroll(RecyclerView.SmoothScroller smoothScroller). The library uses a custom LayoutManager to adjust items' positions on the screen and handle scroll, however it is not exposed to the clientĬode. Smooth scroll to the specified adapter position. Please see the sample app for examples of library usage. If the problem is still present, it's likely somewhere in your code. By doing so you maximize the chance that I will fix the problem.īy the way, before reporting a problem, try replacing DiscreteScrollView with a RecyclerView. If you are going to report an issue, I will greatly appreciate you including some code which I can run to see the issue. Compile 'com.yarolegovich:discrete-scrollview:1.5.1'
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