Develop Reference

How to smooth scroll RecyclerView if item is not fully visible

I want to implement this
.
I want to check if the clicked item is fully visible and if it's not I would like to smoothly scroll upwards/downwards. I have a GridLayoutManager with 3 columns. The items are all of the same size, and are just ImageViews.
I am able to get the RecyclerView to scroll with:
#Override
public void onClick(View view) {
int adapterPosition = RecHolder.this.getAdapterPosition();
mRecyclerView.scrollToPosition(adapterPosition);
...
}
But it's not a "scroll", it's very laggish and way too quick.
If I try to use mRecyclerView.smoothScrollToPosition(adapterPosition); the result is the same. Exactly the same movement, there is no visible difference.

Don't bother testing to see if it's not completely visible. Just insert a command to scroll to that position. Since you didn't post any of your code I can't specifically say how you would do it. I personally have my adapter create an intent and my activity handles the intent. If that's what you're doing then you can include the getAdapterPosition() as an extra like this (vh is my ViewHolder).
vh.mImageView.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
SelectItemGridAdapter.ContentViewHolder vh = (SelectItemGridAdapter.ContentViewHolder) (((View)v.getParent()).getTag());
Intent intent = new Intent(ACTION_SELECT_Item);
intent.putExtra(Constants.MSG_TYPE, SELECT_ITEM_TAPPED);
intent.putExtra(SELECT_ITEM_TAPPED_ID, vh.viewModel.mItemId);
intent.putExtra(SELECT_ITEM_TAPPED_POS, vh.getAdapterPosition());
LocalBroadcastManager.getInstance(mContext).sendBroadcast(intent);
}
});
Then the reveiver in the activity can get the SELECT_ITEM_TAPPED_POS value...
int pos = intent.getIntExtra(SelectItemGridAdapter.SELECT_ITEM_TAPPED_POS, -1);
if (pos > -1)
rv.scrollToPosition(pos);
HTH, Mike

Android Espresso GridView scroll to each item and perform a click on them

I have a GridView loaded with data, and some items in the grid are "group" items
that contain a different set of data. The GridView can scroll if there is
a lot of data.
On some devices the GridView has three columns and on others there are only two columns depending on the device screen width.
What I need to test is to scroll to a particular(with text) item in the grid, open it and then close it(back button=simpleClick). Then scroll to a second item with a particular text and open and then close it(back button=simpleClick).
I have tried several approaches with swipes, and then performing clicks
on them, but this approach fails as you need to know exactly how many
swipes/scrolls to perform before I can click to open the item group - device specific which is bad. Also performing too many scrolls than what is required to reach the bottom of the screen seems to slowdown the test !!quite!! a bit.
private void scrollDown() {
Log.d(TAG, "scrollDown: ");
onView(withId(R.id.main_grid))
.perform(swipeUp());
}
private void scrollUp() {
Log.d(TAG, "scrollUp: ");
onView(withId(R.id.main_grid))
.perform(swipeDown());
}
private void clickOn(final String text) {
onView(withText(new Matcher<String>() {
#Override
public boolean matches(Object item) {
if (item instanceof String) {
if (((String) item).contains(text))
return true;
else
return false;
}
return false;
}
#Override
public void describeMismatch(Object item, Description mismatchDescription) {
}
#Override
public void _dont_implement_Matcher___instead_extend_BaseMatcher_() {
}
#Override
public void describeTo(Description description) {
}
}))
.perform(click());
}
I have tried this as well, but focus gets set to each Item
but as it reaches the end of the screen, one needs to scroll manually
on the device - it does not scroll the screen.
for (int i = 0 ; i < 20; i++) {
onData(anything())
.inAdapterView(allOf(withId(R.id.main_grid), isDisplayed()))
.atPosition(i)
.check(matches(isDisplayed()));
}
I have also tried using the onData which I cannot get to succeed(compile/build),
as I am using a CursorLoader and a ResourceCursorAdapter.
Any Example to solve my test case would great.

Yes, you should use onData statement to avoid problems with scrolling in GridView. You can take a look at example here - http://droidtestlab.com/adapterView.html
But in your case you will have android.database.Cursor interface as a parameter to onData. Something like this (here you specify that you want to wait for data in GridView where first column is equal "VALUE" and then click at this record):
onData(allOf(is(new BoundedMatcher<Object, Cursor>(Cursor.class) {
#Override
public void describeTo(Description description) {
}
#Override
protected boolean matchesSafely(Cursor cursor) {
return cursor.getString(0).equals("VALUE");
}
}))).inAdapterView(withId(<ADAPTER_ID>)).perform(click());

How to open a new activity which has list of item at specific position in android [duplicate]

How can I programmatically scroll to a specific position in a ListView?
For example, I have a String[] {A,B,C,D....}, and I need to set the top visible item of the ListView to the index 21 of my String[].

For a direct scroll:
getListView().setSelection(21);
For a smooth scroll:
getListView().smoothScrollToPosition(21);

For a SmoothScroll with Scroll duration:
getListView().smoothScrollToPositionFromTop(position,offset,duration);
Parameters
position -> Position to scroll to
offset ---->Desired distance in pixels of position from the top of the view when scrolling is finished
duration-> Number of milliseconds to use for the scroll
Note: From API 11.
HandlerExploit's answer was what I was looking for, but My listview is quite lengthy and also with alphabet scroller. Then I found that the same function can take other parameters as well :)
Edit:(From AFDs suggestion)
To position the current selection:
int h1 = mListView.getHeight();
int h2 = listViewRow.getHeight();
mListView.smoothScrollToPositionFromTop(position, h1/2 - h2/2, duration);

Put your code in handler as follows,
public void timerDelayRunForScroll(long time) {
Handler handler = new Handler();
handler.postDelayed(new Runnable() {
public void run() {
try {
lstView.smoothScrollToPosition(YOUR_POSITION);
} catch (Exception e) {}
}
}, time);
}
and then call this method like,
timerDelayRunForScroll(100);
CHEERS!!!

The Listview scroll will be positioned to top by default, but want to scroll if not visible then use this:
if (listView1.getFirstVisiblePosition() > position || listView1.getLastVisiblePosition() < position)
listView1.setSelection(position);

I have set OnGroupExpandListener and override onGroupExpand() as:
and use setSelectionFromTop() method which
Sets the selected item and positions the selection y pixels from the top edge of the ListView. (If in touch mode, the item will not be selected but it will still be positioned appropriately.) (android docs)
yourlist.setOnGroupExpandListener (new ExpandableListView.OnGroupExpandListener()
{
#Override
public void onGroupExpand(int groupPosition) {
expList.setSelectionFromTop(groupPosition, 0);
//your other code
}
});

If someone looking for a similar functionality like Gmail app,
The Listview scroll will be positioned to top by default. Thanks for the hint.
amalBit.
Just subtract it. That's it.
Handler handler = new Handler();
handler.postDelayed(new Runnable() {
#Override
public void run() {
int h1 = mDrawerList.getHeight();
int h2 = header.getHeight();
mDrawerList.smoothScrollToPosition(h2-h1);
}
}, 1000);

If you want to jump directly to the desired position in a listView just use
listView.setSelection(int position);
and if you want to jump smoothly to the desired position in listView just use
listView.smoothScrollToPosition(int position);

Handling listView scrolling using UP/ Down using.button
If someone is interested in handling listView one row up/down using button. then.
public View.OnClickListener onChk = new View.OnClickListener() {
public void onClick(View v) {
int index = list.getFirstVisiblePosition();
getListView().smoothScrollToPosition(index+1); // For increment.
}
});

This is what worked for me. Combination of answers by amalBit & Melbourne Lopes
public void timerDelayRunForScroll(long time) {
Handler handler = new Handler();
handler.postDelayed(new Runnable() {
public void run() {
try {
int h1 = mListView.getHeight();
int h2 = v.getHeight();
mListView.smoothScrollToPositionFromTop(YOUR_POSITION, h1/2 - h2/2, 500);
} catch (Exception e) {}
}
}, time);
}
and then call this method like:
timerDelayRunForScroll(400);

-If you just want the list to scroll up\dawn to a specific position:
myListView.smoothScrollToPosition(i);
-if you want to get the position of a specific item in myListView:
myListView.getItemAtPosition(i);
-also this myListView.getVerticalScrollbarPosition(i);can helps you.
Good Luck :)

You need two things to precisely define the scroll position of a listView:
To get the current listView Scroll position:
int firstVisiblePosition = listView.getFirstVisiblePosition();
int topEdge=listView.getChildAt(0).getTop(); //This gives how much the top view has been scrolled.
To set the listView Scroll position:
listView.setSelectionFromTop(firstVisiblePosition,0);
// Note the '-' sign for scrollTo..
listView.scrollTo(0,-topEdge);

it is easy
list-view.set selection(you pos);
or you can save your position with SharedPreference and when you start activity
it get preferences and setSeletion to that int

I found this solution to allow the scroll up and down using two different buttons.
As suggested by #Nepster I implement the scroll programmatically using the getFirstVisiblePosition() and getLastVisiblePosition() to get the current position.
final ListView lwresult = (ListView) findViewById(R.id.rds_rdi_mat_list);
.....
if (list.size() > 0) {
ImageButton bnt = (ImageButton) findViewById(R.id.down_action);
bnt.setVisibility(View.VISIBLE);
bnt.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
if(lwresult.getLastVisiblePosition()<lwresult.getAdapter().getCount()){
lwresult.smoothScrollToPosition(lwresult.getLastVisiblePosition()+5);
}else{
lwresult.smoothScrollToPosition(lwresult.getAdapter().getCount());
}
}
});
bnt = (ImageButton) findViewById(R.id.up_action);
bnt.setVisibility(View.VISIBLE);
bnt.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
if(lwresult.getFirstVisiblePosition()>0){
lwresult.smoothScrollToPosition(lwresult.getFirstVisiblePosition()-5);
}else{
lwresult.smoothScrollToPosition(0);
}
}
});
}

Adding items to ListView, maintaining scroll position and NOT seeing a scroll jump

I'm building an interface similar to the Google Hangouts chat interface. New messages are added to the bottom of the list. Scrolling up to the top of the list will trigger a load of previous message history. When the history comes in from the network, those messages are added to the top of the list and should not trigger any kind of scroll from the position the user had stopped when the load was triggered. In other words, a "loading indicator" is shown at the top of the list:
Which is then replaced in-situ with any loaded history.
I have all of this working... except one thing that I've had to resort to reflection to accomplish. There are plenty of questions and answers involving merely saving and restoring a scroll position when adding items to the adapter attached to a ListView. My problem is that when I do something like the following (simplified but should be self-explanatory):
public void addNewItems(List<Item> items) {
final int positionToSave = listView.getFirstVisiblePosition();
adapter.addAll(items);
listView.post(new Runnable() {
#Override
public void run() {
listView.setSelection(positionToSave);
}
});
}
Then what the user will see is a quick flash to the top of the ListView, then a quick flash back to the right location. The problem is fairly obvious and discovered by many people: setSelection() is unhappy until after notifyDataSetChanged() and a redraw of ListView. So we have to post() to the view to give it a chance to draw. But that looks terrible.
I've "fixed" it by using reflection. I hate it. At its core, what I want to accomplish is reset the first position of the ListView without going through the rigamarole of the draw cycle until after I've set the position. To do that, there's a helpful field of ListView: mFirstPosition. By gawd, that's exactly what I need to adjust! Unfortunately, it's package-private. Also unfortunately, there doesn't appear to be any way to set it programmatically or influence it in any way that doesn't involve an invalidate cycle... yielding the ugly behavior.
So, reflection with a fallback on failure:
try {
Field field = AdapterView.class.getDeclaredField("mFirstPosition");
field.setAccessible(true);
field.setInt(listView, positionToSave);
}
catch (Exception e) { // CATCH ALL THE EXCEPTIONS </meme>
e.printStackTrace();
listView.post(new Runnable() {
#Override
public void run() {
listView.setSelection(positionToSave);
}
});
}
}
Does it work? Yes. Is it hideous? Yes. Will it work in the future? Who knows? Is there a better way? That's my question.
How do I accomplish this without reflection?
An answer might be "write your own ListView that can handle this." I'll merely ask whether you've seen the code for ListView.
EDIT: Working solution with no reflection based on Luksprog's comment/answer.
Luksprog recommended an OnPreDrawListener(). Fascinating! I've messed with ViewTreeObservers before, but never one of these. After some messing around, the following type of thing appears to work quite perfectly.
public void addNewItems(List<Item> items) {
final int positionToSave = listView.getFirstVisiblePosition();
adapter.addAll(items);
listView.post(new Runnable() {
#Override
public void run() {
listView.setSelection(positionToSave);
}
});
listView.getViewTreeObserver().addOnPreDrawListener(new OnPreDrawListener() {
#Override
public boolean onPreDraw() {
if(listView.getFirstVisiblePosition() == positionToSave) {
listView.getViewTreeObserver().removeOnPreDrawListener(this);
return true;
}
else {
return false;
}
}
});
}
Very cool.

As I said in my comment, a OnPreDrawlistener could be another option to solve the problem. The idea of using the listener is to skip showing the ListView between the two states(after adding the data and after setting the selection to the right position). In the OnPreDrawListener(set with listViewReference.getViewTreeObserver().addOnPreDrawListener(listener);) you'll check the current visible position of the ListView and test it against the position which the ListView should show. If those don't match then make the listener's method return false to skip the frame and set the selection on the ListView to the right position. Setting the proper selection will trigger the draw listener again, this time the positions will match, in which case you'd unregister the OnPreDrawlistener and return true.

I was breaking up my head until I found a solution similar to this.
Before adding a set of items you have to save top distance of the firstVisible item and after adding the items do setSelectionFromTop().
Here is the code:
// save index and top position
int index = mList.getFirstVisiblePosition();
View v = mList.getChildAt(0);
int top = (v == null) ? 0 : v.getTop();
// for (Item item : items){
mListAdapter.add(item);
}
// restore index and top position
mList.setSelectionFromTop(index, top);
It works without any jump for me with a list of about 500 items :)
I took this code from this SO post: Retaining position in ListView after calling notifyDataSetChanged

The code suggested by the question author works, but it's dangerous.
For instance, this condition:
listView.getFirstVisiblePosition() == positionToSave
may always be true if no items were changed.
I had some problems with this aproach in a situation where any number of elements were added both above and below the current element. So I came up with a sligtly improved version:
/* This listener will block any listView redraws utils unlock() is called */
private class ListViewPredrawListener implements OnPreDrawListener {
private View view;
private boolean locked;
private ListViewPredrawListener(View view) {
this.view = view;
}
public void lock() {
if (!locked) {
locked = true;
view.getViewTreeObserver().addOnPreDrawListener(this);
}
}
public void unlock() {
if (locked) {
locked = false;
view.getViewTreeObserver().removeOnPreDrawListener(this);
}
}
#Override
public boolean onPreDraw() {
return false;
}
}
/* Method inside our BaseAdapter */
private updateList(List<Item> newItems) {
int pos = listView.getFirstVisiblePosition();
View cell = listView.getChildAt(pos);
String savedId = adapter.getItemId(pos); // item the user is currently looking at
savedPositionOffset = cell == null ? 0 : cell.getTop(); // current item top offset
// Now we block listView drawing until after setSelectionFromTop() is called
final ListViewPredrawListener predrawListener = new ListViewPredrawListener(listView);
predrawListener.lock();
// We have no idea what changed between items and newItems, the only assumption
// that we make is that item with savedId is still in the newItems list
items = newItems;
notifyDataSetChanged();
// or for ArrayAdapter:
//clear();
//addAll(newItems);
listView.post(new Runnable() {
#Override
public void run() {
// Now we can finally unlock listView drawing
// Note that this code will always be executed
predrawListener.unlock();
int newPosition = ...; // Calculate new position based on the savedId
listView.setSelectionFromTop(newPosition, savedPositionOffset);
}
});
}

Android ListView : How to keep the ListView at the top when its content changes?

I have a view that contains a ListView which is bound to a cursor adapter. When The cursor content change I want to keep the ListView at the top then in my custom cursor adapter I added :
#Override
protected void onContentChanged() {
// ...
myListView.scrollTo(0, 0);
}
but this doesn't work. Then I read somewhere to queue this action like this :
myListView.post(new Runnable() {
public void run() {
myListView.scrollTo(0, 0);
}
});
but this doesn't work either.
How can I keep the ListView at the top when its content changes?
EDIT:
Just for try, I added a button and called scrollTo() in its onClickListener and it didn't work! What am I missing ?

Instead of scrollTo, try setSelection(0) to get to the top position of list view.

i made functions that could be useful for others for listview scrolling, they work for me in every android version, emulator and device, here itemheight is the fixed height of view in the listview.
int itemheight=60;
public void scrollToY(int position)
{
int item=(int)Math.floor(position/itemheight);
int scroll=(int) ((item*itemheight)-position);
this.setSelectionFromTop(item, scroll);// Important
}
public void scrollByY(int position)
{
position+=getListScrollY();
int item=(int)Math.floor(position/itemheight);
int scroll=(int) ((item*itemheight)-position);
this.setSelectionFromTop(item, scroll);// Important
}
public int getListScrollY()
{
try{
//int tempscroll=this.getFirstVisiblePosition()*itemheight;// Important
View v=this.getChildAt(0);
int tempscroll=(this.getFirstVisiblePosition()*itemheight)-v.getTop();// Important
return tempscroll;
}catch(Exception e){}
return 0;
}

ListView's scrollTo applies to the ListView it self as a View
setSelection(0) does the trick because it applies to the listview's adapter