Develop Reference

how to control Android ScrollView to go all the way to top or bottom but never middle?

I have a fragment with a scrollview that holds a long layout essentially representing 2 different sections that are related, what I want is to control the scrollview so when the user wants to scroll down it always goes all the way down and can never be in the middle so it will never reveal partially the top or bottom parts, same effect backwards when you want to scroll up it just takes over and goes all the way up to reveal the top section of the layout fully.
It is basically how a vertical viewpager will behave but contained within a single long view.
I know how to programatically scroll up or down but I don't know how to avoid the user scrolling to just the middle, I'd like to hook up to some scroll event, detect the direction and go fully in either direction.

android animate recycler view first item

I'm trying to do a recycler view animation on scroll, but im struggling to get it started.
Basically, the animation will happen on scroll and always on the first visible child (and only on this one). When the user scrolls the recycler view, second item should overlap the first, and the first will slowly fade out. reverse animation when sliding down.
In short, when the list scroll top for example, when the first item goes offscreen and want to change that behaviour. Instead of going offscreen, it slowly fades based on scroll dY and stay in the same position.
Any hints would be much appreciated.

I think this answer may can help you. I used code like this in my app and work smootly.
https://stackoverflow.com/a/29714138/2971619
Hope to be usefull for you too!

How can I implement a horizontal scroll view where it aligns to each view inside when scrolled

I'm trying to have a horizontal scroll view contain, for example, three vertical scroll views. And what I want is to be able to have the horizontal scroll view align to each vertical scroll view when you scroll over to it.
I'm not sure if a horizontal scroll view is the correct way to implement this kind of feature, however I found the method scrollTo(x,y) which I think may be in the right direction to creating this.
The best example of what I'm trying to do is shopping for music in the google play store (atleast, on my nexus 7). It allows you to scroll left or right, and it aligns to a screen's worth of content, which you can then vertically scroll.
So, that's what I'm trying to recreate in my app. But I'm confused on implementation details of allowing the horizontal scroll view, to scroll, and stop at a certain point. It looks like I need to override HorizontalScrollView to capture the motion events, but I feel like that's too complex for what seems like a simple task.
Does my question make sense? I basically am at the very starting point of creating this, and need some help as to where to go next.

Scroll ListView smoothly and programmatically

I have searched a lot but I couldn't find an answer.
I want to implement something like in Go Launcher. When you drag an icon in app drawer and move it out of container top or bottom bound, the list begins to scroll.
So far, I have tried following things:
Dispatch touch events to simulate scrolling - impossible while touching the screen
Use smoothScrollBy() method - almost there, but it scrolls only screen height distance
Use scrollBy() - it moves only the container and leaves blank space. I would put there some rows if only I could be able to reuse views that went off the screen.
I need the ListView to scroll SMOOTHLY.
So here goes ma question. Anybody knows how can it be done? I'll put a gratitude in About section of my app to person who will help me:)

using listview and try scrollToPosition（），or smoothscrollBy（）

Android: Detect when ScrollView has finished scrolling and bouncing back?

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).