I'm developing a chat application and I'm trying to load 10 messages at a time, and when the user scrolls up it loads 10 more. therefore I used stackFromBottom=true to load the messages from the bottom :
<ListView
android:id="#+id/messagesList"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:transcriptMode="normal"
android:stackFromBottom="true">
And I have a scroll listener to know when the user reached the top (firstVisibleItem == 0 , i.e the first message) so I can load more messages:
messagesList.setOnScrollListener(new AbsListView.OnScrollListener() {
#Override
public void onScrollStateChanged(AbsListView absListView, int i) {
}
#Override
public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
if (firstVisibleItem ==0 && !loading && !startApp) {
loading = true;
skip += 10;
fetchMessages = new FetchMessages(); //load more items
fetchMessages.execute(true);
}
}
});
The issue is when you scroll up and reach the top, 10 more messages load but the Listview automatically scrolls to the bottom. I want to stay in the exact same position when new items are added to the Listview, just like any regular chat application.
This is the add messages method:
#Override
protected void onPostExecute(String json) {
if(json!=null){
...
//After Parse JSON ...
chatMessageAdapter.list.add(0,chatMessage); //add the message to the top of the list
chatMessageAdapter.notifyDataSetChanged(); //listview scrolls to the bottom afterwards
}
loading = false;
startApp = false;
}
I tried many of the suggestions in other threads but none of them actually worked. I hope someone could help here.
Many thanks.
what did work for me was that:
// save index and top position
int index = mList.getFirstVisiblePosition();
View v = mList.getChildAt(0);
int top = (v == null) ? 0 : v.getTop();
// notify dataset changed or re-assign adapter here
// restore the position of listview
mList.setSelectionFromTop(index, top);
Do note you have to remove android:transcriptMode="normal" from your xml, otherwise it wouldn't work.
Related
I have a ListView with a set of children vertically listed (View objects) to be viewed by the users. I have to track the the user views, say,
a. If a user views a set of items for around 1 second, I should track the impressions.
b. If the same user scrolls the items out of the viewport and return back, I should track again, if he viewed for 1 second.
I tried several options like getGlobalVisibleRect(), getLocalVisibleRect(), getLocationOnScreen() and they are confusing in the first place and didn't help me get the right coordinates and visibility of the child items of the listView.
I checked Track impression of items in an android ListView which is a bit similar to my requirement but I thought to check if there is a better solution. I am new to Android and apologies if I am not clear on some explanations
To get your desired result, I think we have two different solutions. First, create Handler for each of the item and call / remove in scroll view if it is visible. But this is very much stupid one as creating so many Handlers will make your app's life hell.
Second and best way is to use call / remove a single Handler for the entire visible items. If it persist for a time "A second" (1 second for you), use impression count in each of your item's model class and increase it with ++ operator.
You can add scroll listener in your listivew. The script will be like-
ListView listView = null;
int firstVisibleItemIndex = 0;
int visibleCount = 0;
Handler handler = new Handler();
Runnable runnable = new Runnable() {
#Override
public void run() {
for (int i = firstVisibleItemIndex; i < firstVisibleItemIndex + visibleCount; i++) {
try {
//Get impression count from model for the visible item index i
int count = modelList.get(i).getImpressionCount();
//Set impression count to the model for the visible item index i
modelList.get(i).setImpressionCount(++count);
} catch (Exception e) {
e.printStackTrace();
}
}
}
};
//Can call this method body in onCreate directly
private void addListScrollListener() {
listView.setOnScrollListener(new AbsListView.OnScrollListener() {
#Override
public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
// You cat determine first and last visible items here
// final int lastVisibleItem = firstVisibleItem + visibleItemCount - 1;
handler.removeCallbacks(runnable);
firstVisibleItemIndex = firstVisibleItem;
visibleCount = visibleItemCount;
handler.postDelayed(runnable, 1000);
}
#Override
public void onScrollStateChanged(AbsListView arg0, int arg1) {
// TODO Auto-generated method stub
}
});
}
I assume that you will bind your ListView with the id in your onCreate method. Also you can call the listener thing in your onCreate after binding the view with the variable.
I hope this will work for your requirement.
Let me know your feedback.
I am building an application like techcrunch.
I am fetching data from server in JSON format and displaying the data in list view like article title,author name and image.
I have applied pagination means when user scroll more articles load in a list view. My pagination works fine but there is an issue in the scroll function as the fresh or new data loads the scroll dose not aligns with the data.
To clarify more in simple words my scroll-er goes at the top of the page when i am actually scrolling down
this is my code :
listView.setOnScrollListener(new AbsListView.OnScrollListener()
{
#Override
public void onScrollStateChanged(AbsListView absListView, int i)
{
}
#Override
public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount)
{
int lastItem = firstVisibleItem + visibleItemCount;
if(lastItem == totalItemCount){
if (mPreLast != lastItem)
{
mPreLast = lastItem;
onStart();
}
}
}
});`
You can use:
listView.setSelectionFromTop(newPosition, 0);
With this method you can set the position to a ListView, using the first parameter as the new position on the list, and the second parameter can be used to set the distance from the top
i have gridview with two column
user can scroll vertically to see gridview items
the problem is when user scrolling is finished
the first visible row is not completely seen .i want to set top of first visible row to top of gridview so first row is comletely visible
can anyone help me?
Update:
the first item is
and the second item is
but after scroll we see
you can try this
grid.setOnScrollListener(new OnScrollListener() {
#Override
public void onScrollStateChanged(AbsListView arg0, int scrollState) {
//this is the state when scroll finish
if(scrollState==SCROLL_STATE_IDLE)
//the first visible item is the first (even partially) visbile item
//setSelection will scroll the grid to the beginning of such item
grid.setSelection(firstVisibleItem);
}
#Override
public void onScroll(AbsListView arg0, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
}
});
I use RecyclerView, and i hope it's good for you!
mLayoutManager = new GridLayoutManager(getActivity(), 2);
mListRV= (RecyclerView).findViewById(R.id.list_rv);
mListRV.setLayoutManager(mLayoutManager);
mListRV.setOnScrollListener(new RecyclerView.OnScrollListener() {
#Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
if (newState == RecyclerView.SCROLL_STATE_IDLE) {
View v = mLayoutManager.getChildAt(0);
int offsetTop = v.getTop();
int offsetBottom = v.getBottom();
int height = (offsetBottom - offsetTop);
if(offsetTop >= -height/2) {
mListRV.smoothScrollBy(0, offsetTop);
} else {
mListRV.smoothScrollBy(0, height + offsetTop);
}
}
}
});
With this code, when you finish scroll, if the first visible item only show a part in recyclerView. It will auto scroll to show full item. You can use:
mLayoutManager.scrollToPositionWithOffset(position, offset);
But it is so fast, the user can be confused. And you will not need use customLayoutManager to edit scroll's properties.
Hope that helps for you!
I have a listview with a bunch of items of different sizes
I have a button to scroll to a certain item in the listview
however, when this item is last, the listview of course stops when this item becomes visible
but I want the listview to scroll up in such a way that this last item is the only visible item on the screen - and the bottom of the list is blank
how do I do this?
my scroll method:
public void scrollTo(int newPosition) {
lv.smoothScrollToPositionFromTop(newPosition+ 1, 0, 500);
handler.postDelayed(new Runnable() {
#Override
public void run() {
//this is needed in order for the item to be at the top
//because the listview stops, if scrolling from top down, and stops
//once item becomes visible
lv.smoothScrollToPositionFromTop(newPoisition+ 1, 0, 0);
}
}, 501);
}
this is the crash report for adding a dummy item manually
Well, you can do this in the following way:
Detect the end of the list view.
When the list view reached the end, keep the last one in the list(array list that is used to populate the list) and the delete all others and refresh the list. If you do not want to delete them, simply copy to another array list and copy back the items, if the user needs to move up again.
To detect the end of the list view you can use the following class:
public final class GVOnScrollListener implements AbsListView.OnScrollListener {
public void onScroll(AbsListView view, int firstVisibleItem,
int visibleItemCount, int totalItemCount) {
if (loading) {
if (totalItemCount > previousTotal) {
loading = false;
previousTotal = totalItemCount;
offset++;
}
}
if (!loading && totalItemCount == (firstVisibleItem + visibleItemCount) && (productCount > totalItemCount)) {
productListServiceRequest();
businessResultListView.setSelection(firstVisibleItem);
loading = true;
new Handler().postDelayed(new Runnable() {
public void run() {
readyToRequest = true;
}
}, 2000);
readyToRequest = false;
}
}
public void onScrollStateChanged(AbsListView view, int scrollState) {
}
}
and set it to the list view like:
listview.setAdapter(businessPromotionListAdapter);
With the above class, you can see:
Number of items that you can see in the screen.
Number of items that you have scrolled up.
Total number of items in the list.
I need to check all element on a ListView to set a label only to a one of those.
I can't edit the database or the adapter, I just want to scroll the ListView to perform a check and set a string on a TextView.
#Override
protected void onResume(){
super.onResume();
...
cursor = getCursor();
startManagingCursor(cursor);
adapter = new SimpleCursorAdapter(this,R.layout.profile_item_layout,cursor,from,to);
lst_profiles.setAdapter(adapter);
SharedPreferences customSharedPreference = PreferenceManager.getDefaultSharedPreferences(ProfilerActivity.this.getApplicationContext());
long current = customSharedPreference.getLong(ProfileManager.CURRENT, -1);
toast(lst_profiles.getChildCount()); //display 0
if(current!=-1){
for(int i=0;i<lst_profiles.getChildCount();i++){
if(lst_profiles.getItemIdAtPosition(i)==current)
((TextView)lst_profiles.getChildAt(i).findViewById(R.id.activeLabel)).setText(getString(R.string.active));
else
((TextView)lst_profiles.getChildAt(i).findViewById(R.id.activeLabel)).setText("");
}
}
}
How can I do? I need to wait something?
P.S. Obviusly the ListView is not empty.
That seems to be a nasty hack. But okay...
The thing is, that your list won't have children as long as the list is not displayed to the user. But you have to understand that getChildCount will return the amount of visible list items (so maybe about 10 views) and the position of them will never relate to the actual item position in the adapter.
If you really need to communicate with the views on a such low level you could try to attach a scroll listener to your list:
#Override
public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
for (int i = 0; i < visibleItemCount; i++) {
View child = getChildAt(i);
// i + firstVisibleItem == the actual item position in the adapter
}
}