Develop Reference

ListView overlay another layout when scroll

Actually I don't know how it properly called - overlay, parallax or slideUP, whatever, I have an Activity called "cafe details" which presents a Container(LinearLayout) with header information (name, min price, delivery time min e.t.c) and other container (ViewPager) which contains a ExpandableListView with something information (menus&dishes) and all I want to do is slide up my Viewpager when scrolls listview to scpecific Y position to cover(or overlay) header information.
A similar effect (but with parallax that I don't need to use) looks like this
I can detect when user scrolling listview down or up but how I can move container with ViewPager to overlay other container? Please give me ideas, regards.
UPD
I have tried a huge number of ways how to implement it and all of them unfortunately are not suitable. So now I have come to next variant - add scroll listener to ListView, calculate scrollY position of view and then based on that move the viewpager on y axis by calling setTranslationY();
Here is some code
1) ViewPager's fragment
mListView.setOnScrollListener(new AbsListView.OnScrollListener() {
#Override
public void onScrollStateChanged(AbsListView absListView, int i) {
}
#Override
public void onScroll(AbsListView absListView, int i, int i1, int i2) {
if (getActivity() != null) {
((MainActivity) getActivity()).resizePagerContainer(absListView);
}
}
});
2) MainActivity
//object fields
int previousPos;
private float minTranslation;
private float minHeight;
<--------somewhere in onCreate
minTranslation = - (llVendorDescHeaders.getMeasuredHeight()+llVendorDescNote.getMeasuredHeight());
//llVendorDescHeaders is linearLayout with headers that should be hidden
//lVendorDescNote is a textView on green background;
minHeight = llVendorDescriptionPagerContainer.getMeasuredHeight();
//llVendorDescriptionPagerContainer is a container which contains ViewPager
--------->
public void resizePagerContainer(AbsListView absListView){
final int scrollY = getScrollY(absListView);
if (scrollY != previousPos) {
final float translationY = Math.max(-scrollY, minTranslation);
llVendorDescriptionPagerContainer.setTranslationY(translationY);
previousPos = scrollY;
}
}
private int getScrollY(AbsListView view) {
View child = view.getChildAt(0);
if (child == null) {
return 0;
}
int firstVisiblePosition = view.getFirstVisiblePosition();
int top = child.getTop();
return -top + firstVisiblePosition * child.getHeight() ;
}
This simple solution unfortunately has a problem - it is blinking and twitching (I don't know how to call it right) when scrolls slowly. So instead setTranslationY() I've used an objectAnimator:
public void resizePagerContainer(AbsListView absListView){
.............
ObjectAnimator moveAnim = ObjectAnimator.ofFloat(llVendorDescriptionPagerContainer, "translationY", translationY);
moveAnim.start();
..............
}
I don't like this solution because 1) anyway it does resize viewpager with delay, not instantly 2) I don't think that is good idea to create many ObjectAnimator's objects every time when I scroll my listView.
Need your help and fresh ideas. Regards.

I'm assuming that you are scrolling the top header (the ImageView is a child of the header) based on the scrollY of the ListView/ScrollView, as shown below:
float translationY = Math.max(-scrollY, mMinHeaderTranslation);
mHeader.setTranslationY(translationY);
mTopImage.setTranslationY(-translationY / 3); // For parallax effect
If you want to stick the header/image to a certain dimension and continue the scrolling without moving it anymore, then you can change the value of mMinHeaderTranslation to achieve that effect.
//change this value to increase the dimension of header stuck on the top
int tabHeight = getResources().getDimensionPixelSize(R.dimen.tab_height);
mHeaderHeight = getResources().getDimensionPixelSize(R.dimen.header_height);
mMinHeaderTranslation = -mHeaderHeight + tabHeight;
The code snippets above are in reference to my demo but I think it's still general enough for you.
If you're interested you can check out my demo
https://github.com/boxme/ParallaxHeaderViewPager

Have you tried CoordinatorLayout from this new android's design support library? It looks like it's what you need. Check this video from 3:40 or this blog post.

Fix the Animation of a Circular ViewPager

Goal
Build a Circular ViewPager.
The first element lets you peak to the last element and swipe to it, and vice versa. You should be able to swipe in either direction forever.
Now this has been accomplished before, but these questions do not work for my implementation. Here are a few for reference:
how to create circular viewpager?
ViewPager as a circular queue / wrapping
https://github.com/antonyt/InfiniteViewPager
How I Tried to Solve the Problem
We will use an array of size 7 as an example. The elements are as follows:
[0][1][2][3][4][5][6]
When you are at element 0, ViewPagers do not let you swipe left! How terrible :(. To get around this, I added 1 element to the front and end.
[0][1][2][3][4][5][6] // Original
[0][1][2][3][4][5][6][7][8] // New mapping
When the ViewPageAdapter asks for (instantiateItem()) element 0, we return element 7. When the ViewPageAdapter asks for element 8 we return element 1.
Likewise in the OnPageChangeListener in the ViewPager, when the onPageSelected is called with 0, we setCurrentItem(7), and when it's called with 8 we setCurrentItem(1).
This works.
The Problem
When you swipe to the left from 1 to 0, and we setCurrentItem(7), it will animate all the way to right by 6 full screens. This doesn't give the appearance of a circular ViewPager, it gives the appearence rushing to the last element in the opposite direction the user requested with their swipe motion!
This is very very jarring.
How I Tried to Solve This
My first inclination was to turn off smooth (ie, all) animations. It's a bit better, but it's now choppy when you move from the last element to the first and vice versa.
I then made my own Scroller.
http://developer.android.com/reference/android/widget/Scroller.html
What I found was that there is always 1 call to startScroll() when moving between elements, except when I move from 1 to 7 and 7 to 1.
The first call is the correct animation in direction and amount.
The second call is the animation that moves everything to the right by multiple pages.
This is where things got really tricky.
I thought the solution was to just skip the second animation. So I did. What happens is a smooth animation from 1 to 7 with 0 hiccups. Perfect! However, if you swipe, or even tap the screen, you are suddenly (with no animation) at element 6! If you had swiped from 7 to 1, you'll actually be at element 2. There is no call to setCurrentItem(2) or even a call to the OnPageChangeListener indicating that you arrived at 2 at any point in time.
But you're not actually at element 2, which is kind of good. You are still at element 1, but the view for element 2 will be shown. And then when you swipe to the left, you go to element 1. Even though you were really at element 1 already.. How about some code to help clear things up:
Animation is broken, but no weird side effects
#Override
public void startScroll(int startX, int startY, int dx, int dy, int duration) {
super.startScroll(startX, startY, dx, dy, duration);
}
Animation works! But everything is strange and scary...
#Override
public void startScroll(int startX, int startY, int dx, int dy, int duration) {
if (dx > 480 || dx < -480) {
} else {
super.startScroll(startX, startY, dx, dy, duration);
}
}
The ONLY difference is that when the second animation (bigger than the width of the 480 pixel screen) is called, we ignore it.
After reading through the Android Source code for Scroller, I found that startScroll does not start scrolling anything. It sets up all the data to be scrolled, but doesn't initiate anything.
My Hunch
When you do the circular action (1 to 7 or 7 to 1), there are two calls to startScroll(). I think something in between the two calls is causing an issue.
User scrolls from element 1 to element 7 causing a jump from 0 to 7. This should animate to the left.
startScroll() is called indicating a short animation to the left.
STUFF HAPPENS THAT MAKES ME CRY PROBABLY I THINK
startScroll() is called indicating a long animation to the right.
Long animation to the right occurs.
If I comment out 4, then 5 becomes "Short correct animation to the left, things go crazy"
Summary
My implementation of a Circular ViewPager works, but the animation is broken. Upon trying to fix the animation, it breaks the functionality of the ViewPager. I am currently spinning my wheels trying to figure out how to make it work. Help me! :)
If anything is unclear please comment below and I will clarify. I realize I was not very precise with how things are broken. It's difficult to describe because it's not even clear what I'm seeing on the screen. If my explanation is an issue I can work on it, let me know!
Cheers,
Coltin
Code
This code is slightly modified to make it more readable on its own, though the functionality is identical to my current iteration of the code.
OnPageChangeListener.onPageSelected
#Override
public void onPageSelected(int _position) {
boolean animate = true;
if (_position < 1) {
// Swiping left past the first element, go to element (9 - 2)=7
setCurrentItem(getAdapter().getCount() - 2, animate);
} else if (_position >= getAdapter().getCount() - 1) {
// Swiping right past the last element
setCurrentItem(1, animate);
}
}
CircularScroller.startScroll
#Override
public void startScroll(int _startX, int _startY, int _dx, int _dy, int _duration) {
// 480 is the width of the screen
if (dx > 480 || dx < -480) {
// Doing nothing in this block shows the correct animation,
// but it causes the issues mentioned above
// Uncomment to do the big scroll!
// super.startScroll(_startX, _startY, _dx, _dy, _duration);
// lastDX was to attempt to reset the scroll to be the previous
// correct scroll distance; it had no effect
// super.startScroll(_startX, _startY, lastDx, _dy, _duration);
} else {
lastDx = _dx;
super.startScroll(_startX, _startY, _dx, _dy, _duration);
}
}
CircularViewPageAdapter.CircularViewPageAdapter
private static final int m_Length = 7; // For our example only
private static Context m_Context;
private boolean[] created = null; // Not the best practice..
public CircularViewPageAdapter(Context _context) {
m_Context = _context;
created = new boolean[m_Length];
for (int i = 0; i < m_Length; i++) {
// So that we do not create things multiple times
// I thought this was causing my issues, but it was not
created[i] = false;
}
}
CircularViewPageAdapter.getCount
#Override
public int getCount() {
return m_Length + 2;
}
CircularViewPageAdapter.instantiateItem
#Override
public Object instantiateItem(View _collection, int _position) {
int virtualPosition = getVirtualPosition(_position);
if (created[virtualPosition - 1]) {
return null;
}
TextView tv = new TextView(m_Context);
// The first view is element 1 with label 0! :)
tv.setText("Bonjour, merci! " + (virtualPosition - 1));
tv.setTextColor(Color.WHITE);
tv.setTextSize(30);
((ViewPager) _collection).addView(tv, 0);
return tv;
}
CircularViewPageAdapter.destroyItem
#Override
public void destroyItem(ViewGroup container, int position, Object view) {
ViewPager viewPager = (ViewPager) container;
// If the virtual distance is distance 2 away, it should be destroyed.
// If it's not intuitive why this is the case, please comment below
// and I will clarify
int virtualDistance = getVirtualDistance(viewPager.getCurrentItem(), getVirtualPosition(position));
if ((virtualDistance == 2) || ((m_Length - virtualDistance) == 2)) {
((ViewPager) container).removeView((View) view);
created[getVirtualPosition(position) - 1] = false;
}
}

I think the best doable approach would be instead of using a normal list to have a wrapper to the List that when the get(pos) method is executed to obtain the object to create the view, you make something like this get(pos % numberOfViews) and when it ask for the size of the List you put that the List is Integer.MAX_VALUE and you start your List in the middle of it so you can say that is mostly impossible to have an error, unless they actually swipe to the same side until the reach the end of the List. I will try to post a proof of concept later this weak if the time allows me to do so.
EDIT:
I have tried this piece of code, i know is a simple textbox shown on each view, but the fact is that it works perfectly, it might be slower depending on the total amount of views but the proof of concept is here. What i have done is that the MAX_NUMBER_VIEWS represents what is the maximum numbers of times a user can completely give before he is stopped. and as you can see i started the viewpager at the length of my array so that would be the second time it appears so you have one turn extra to the left and right but you can change it as you need it. I hope i do not get more negative points for a solution that in fact does work.
ACTIVITY:
pager = (ViewPager)findViewById(R.id.viewpager);
String[] articles = {"ARTICLE 1","ARTICLE 2","ARTICLE 3","ARTICLE 4"};
pager.setAdapter(new ViewPagerAdapter(this, articles));
pager.setCurrentItem(articles.length);
ADAPTER:
public class ViewPagerAdapter extends PagerAdapter {
private Context ctx;
private String[] articles;
private final int MAX_NUMBER_VIEWS = 3;
public ViewPagerAdapter(Context ctx, String[] articles) {
this.ctx = ctx;
this.articles = articles.clone();
}
#Override
public int getCount() {
return articles.length * this.MAX_NUMBER_VIEWS;
}
#Override
public Object instantiateItem(ViewGroup container, int position) {
TextView view = new TextView(ctx);
view.setLayoutParams(new LayoutParams(LayoutParams.MATCH_PARENT,
LayoutParams.MATCH_PARENT));
int realPosition = position % articles.length;
view.setText(this.articles[realPosition]);
((ViewPager) container).addView(view);
return view;
}
#Override
public void destroyItem(ViewGroup container, int position, Object object) {
((ViewPager) container).removeView((View) object);
}
#Override
public boolean isViewFromObject(View view, Object object) {
return view == ((View) object);
}
#Override
public Parcelable saveState() {
return null;
}
}

android: smoothScrollToPosition() not working correctly

I'm trying to smoothly scroll to last element of a list after adding an element to the arrayadapter associated with the listview.
The problem is that it just scrolls to a random position
arrayadapter.add(item);
//DOES NOT WORK CORRECTLY:
listview.smoothScrollToPosition(arrayadapter.getCount()-1);
//WORKS JUST FINE:
listview.setSelection(arrayadapter.getCount()-1);

You probably want to tell the ListView to post the scroll when the UI thread can handle it (which is why yours it not scrolling properly). SmoothScroll needs to do a lot of work, as opposed to just go to a position ignoring velocity/time/etc. (required for an "animation").
Therefore you should do something like:
getListView().post(new Runnable() {
#Override
public void run() {
getListView().smoothScrollToPosition(pos);
}
});

(Copied from my answer: smoothScrollToPositionFromTop() is not always working like it should)
This is a known bug. See https://code.google.com/p/android/issues/detail?id=36062
However, I implemented this workaround that deals with all edge cases that might occur:
First call smothScrollToPositionFromTop(position) and then, when scrolling has finished, call setSelection(position). The latter call corrects the incomplete scrolling by jumping directly to the desired position. Doing so the user still has the impression that it is being animation-scrolled to this position.
I implemented this workaround within two helper methods:
smoothScrollToPosition()
public static void smoothScrollToPosition(final AbsListView view, final int position) {
View child = getChildAtPosition(view, position);
// There's no need to scroll if child is already at top or view is already scrolled to its end
if ((child != null) && ((child.getTop() == 0) || ((child.getTop() > 0) && !view.canScrollVertically(1)))) {
return;
}
view.setOnScrollListener(new AbsListView.OnScrollListener() {
#Override
public void onScrollStateChanged(final AbsListView view, final int scrollState) {
if (scrollState == SCROLL_STATE_IDLE) {
view.setOnScrollListener(null);
// Fix for scrolling bug
new Handler().post(new Runnable() {
#Override
public void run() {
view.setSelection(position);
}
});
}
}
#Override
public void onScroll(final AbsListView view, final int firstVisibleItem, final int visibleItemCount,
final int totalItemCount) { }
});
// Perform scrolling to position
new Handler().post(new Runnable() {
#Override
public void run() {
view.smoothScrollToPositionFromTop(position, 0);
}
});
}
getChildAtPosition()
public static View getChildAtPosition(final AdapterView view, final int position) {
final int index = position - view.getFirstVisiblePosition();
if ((index >= 0) && (index < view.getChildCount())) {
return view.getChildAt(index);
} else {
return null;
}
}

You should use setSelection() method.

Use LayoutManager to smooth scroll
layoutManager.smoothScrollToPosition(recyclerView, new RecyclerView.State(), position);

final Handler handler = new Handler();
//100ms wait to scroll to item after applying changes
handler.postDelayed(new Runnable() {
#Override
public void run() {
listView.smoothScrollToPosition(selectedPosition);
}}, 100);

The set selection method mentioned by Lars works, but the animation was too jumpy for our purposes as it skips whatever was left. Another solution is to recall the method repeatedly until the first visible position is your index. This is best done quickly and with a limit as it will fight the user scrolling the view otherwise.
private void DeterminedScrollTo(Android.Widget.ListView listView, int index, int attempts = 0) {
if (listView.FirstVisiblePosition != index && attempts < 10) {
attempts++;
listView.SmoothScrollToPositionFromTop (index, 1, 100);
listView.PostDelayed (() => {
DeterminedScrollTo (listView, index, attempts);
}, 100);
}
}
Solution is in C# via. Xamarin but should translate easily to Java.

Do you call arrayadapter.notifyDataSetChanged() after you called arrayadapter.add()? Also to be sure, smoothScrollToPosition and setSelection are methods available in ListView not arrayadapter as you have mentioned above.
In any case see if this helps:
smoothScrollToPosition after notifyDataSetChanged not working in android

Solution in kotlin:
fun AbsListView.scrollToIndex(index: Int, duration: Int = 150) {
smoothScrollToPositionFromTop(index, 0, duration)
postDelayed({
setSelection(index)
post { smoothScrollToPositionFromTop(index, 0, duration) }
}, duration.toLong())
}
PS: Looks like its quite messed up on Android SDK side so this is kind of best you can get, if you don't want to calculate your view offset manually. Maybe best easy way is to set duration to 0 for long list to avoid any visible jump.
I had some issues when calling just setSelection in some positions in GridView so this really seems to me as solution instead of using that.

use this in android java, it work for me:
private void DeterminedScrollTo(int index, int attempts) {
if (listView.getFirstVisiblePosition() != index && attempts < 10) {
attempts++;
if (listView.canScrollVertically(pos))
listView.smoothScrollToPositionFromTop(index, 1, 200);
int finalAttempts = attempts;
new Handler(Looper.getMainLooper()).postDelayed(new Runnable() {
#Override
public void run() {
DeterminedScrollTo(index, finalAttempts);
}
}, 200);
}
}

Wait unitl ListView's smoothScrollToPosition() finishes

Scope
I need to scroll to certain position smoothly and then "jump" to another position with setSelection(anotherPosition). This is done to create an illusion of smooth scrolling of (e.g.) 100 items in ListView. smoothScrollToPosition(100) lasts too much, you know.
Problem
setSelection() doesn't wait till smoothScrollToPosition finishes its work, so setSelection() is being called immediately and user sees quick jumping only;
Code
private final int scrollableItems = 20;
int firstVisiblePosition = mListView.getFirstVisiblePosition();
if (firstVisiblePosition < scrollableItems) {
mListView.smoothScrollToPosition(0);
} else {
mListView.smoothScrollToPosition(firstVisiblePosition - scrollableItems);
mListView.setSelection(0);
}
mListView.clearFocus();
Idea
OK, we could change logic of smoothness illusion: first setSelection(), then scroll smoothly (we're scrolling to the very first item on top of the list):
int firstVisiblePosition = mListView.getFirstVisiblePosition();
if (firstVisiblePosition < scrollableItems) {
mListView.smoothScrollToPosition(0);
} else {
mListView.setSelection(scrollableItems);
mListView.smoothScrollToPosition(0);
}
mListView.clearFocus();

final ListView listView = ...;
View listItemView = ...;
listView.smoothScrollBy(listItemView.getHeight() * NUMBER_OF_VIEWS,
DURATION * 2);
listView.postDelayed(new Runnable() {
public void run() {
listView.smoothScrollBy(0, 0); // Stops the listview from overshooting.
listView.setSelection(0);
}
}, DURATION);
Of course, direction of the scroll etc. would need to be adjusted for your use case (go to the top of the list)
EDIT: Old solution could overshoot if the velocity of the scroll was too high, smoothScrollBy(0,0) will stop the smooth scrolling before setting the selection properly and immediately.

Another way is to add an OnScrollListener.
private final int scrollableItems = 20;
int firstVisiblePosition = mListView.getFirstVisiblePosition();
if (firstVisiblePosition < scrollableItems) {
mListView.smoothScrollToPosition(0);
} else {
mListView.setOnScrollListener(new AbsListView.OnScrollListener() {
#Override
public void onScrollStateChanged(AbsListView absListView, int i) {
if (i == SCROLL_STATE_IDLE) {
mListView.setSelection(0);
}
}
})
mListView.smoothScrollToPosition(firstVisiblePosition - scrollableItems);
}
mListView.clearFocus();

List view snap to item

I'm creating a list of pictures using a ListView and the photos are of a size that would fit 2 to 3 photos on the screen.
The problem that I'm having is that I would like to when the user stops scrolling that the first item of the visible list would snap to the top of screen, for example, if the scroll ends and small part of the first picture displayed, we scroll the list down so the picture is always fully displayed, if mostly of the picture is displayed, we scroll the list up so the next picture is fully visible.
Is there a way to achieve this in android with the listview?

I've found a way to do this just listening to scroll and change the position when the scroll ended by implementing ListView.OnScrollListener
#Override
public void onScrollStateChanged(AbsListView view, int scrollState) {
switch (scrollState) {
case OnScrollListener.SCROLL_STATE_IDLE:
if (scrolling){
// get first visible item
View itemView = view.getChildAt(0);
int top = Math.abs(itemView.getTop()); // top is a negative value
int bottom = Math.abs(itemView.getBottom());
if (top >= bottom){
((ListView)view).setSelectionFromTop(view.getFirstVisiblePosition()+1, 0);
} else {
((ListView)view).setSelectionFromTop(view.getFirstVisiblePosition(), 0);
}
}
scrolling = false;
break;
case OnScrollListener.SCROLL_STATE_TOUCH_SCROLL:
case OnScrollListener.SCROLL_STATE_FLING:
Log.i("TEST", "SCROLLING");
scrolling = true;
break;
}
}
The change is not so smooth but it works.

Utilizing a couple ideas from #nininho's solution, I got my listview to snap to the item with a smooth scroll instead of abruptly going to it. One caveat is that I've only tested this solution on a Moto X in a basic ListView with text, but it works very well on the device. Nevertheless, I'm confident about this solution, and encourage you to provide feedback.
listview.setOnScrollListener(new OnScrollListener() {
#Override
public void onScrollStateChanged(AbsListView view, int scrollState) {
// TODO Auto-generated method stub
if (scrollState == SCROLL_STATE_IDLE) {
View itemView = view.getChildAt(0);
int top = Math.abs(itemView.getTop());
int bottom = Math.abs(itemView.getBottom());
int scrollBy = top >= bottom ? bottom : -top;
if (scrollBy == 0) {
return;
}
smoothScrollDeferred(scrollBy, (ListView)view);
}
}
private void smoothScrollDeferred(final int scrollByF,
final ListView viewF) {
final Handler h = new Handler();
h.post(new Runnable() {
#Override
public void run() {
// TODO Auto-generated method stub
viewF.smoothScrollBy(scrollByF, 200);
}
});
}
#Override
public void onScroll(AbsListView view, int firstVisibleItem,
int visibleItemCount, int totalItemCount) {
// TODO Auto-generated method stub
}
});
The reason I defer the smooth scrolling is because in my testing, directly calling the smoothScrollBy method in the state changed callback had problems actually scrolling. Also, I don't foresee a fully-tested, robust solution holding very much state, and in my solution below, I hold no state at all. This solution is not yet in the Google Play Store, but should serve as a good starting point.

Using #nininho 's solution,
In the onScrollStateChanged when the state changes to SCROLL_STATE_IDLE, remember the position to snap and raise a flag:
snapTo = view.getFirstVisiblePosition();
shouldSnap = true;
Then, override the computeScroll() method:
#Override
public void computeScroll() {
super.computeScroll();
if(shouldSnap){
this.smoothScrollToPositionFromTop(snapTo, 0);
shouldSnap = false;
}
}

You can do a much more smooth scrolling if you use RecyclerView. The OnScrollListener is way better.
I have made an example here: https://github.com/plattysoft/SnappingList

Well.. I know 10 years have past since this question was asked, but now we can use LinearSnapHelper:
new LinearSnapHelper().attachToRecyclerView(recyclerView);
Source:
https://proandroiddev.com/android-recyclerview-snaphelper-19eaa9598da6

Apart from trying the code above one thing you should make sure of is that your listView have a height that can fit exact number of items you want to be displayed.
e.g
If you want 4 items to be displayed after snap effect and your row height (defined in its layout) should be 1/4 of the total height of the list.

Note that after the smoothScrollBy() call, getFirstVisiblePosition() may point to the list item ABOVE the topmost one in the listview. This is especially true when view.getChildAt(0).getBottom() == 0. I had to call view.setSelection(view.getFirstVisiblePosition() + 1) to remedy this odd behavior.