Develop Reference

How can I know when a custom ListView is scrolling Up?

I can detected when I scroll until the very bottom using
.size() - 1 of my elem. But if I start to scroll up at the middle of the list, how can I know it, in the method GetView() of course.

Found a way to do it which works more or less well...
list.setOnScrollListener(new AbsListView.OnScrollListener() {
private int mLastFirstVisibleItem;
#Override
public void onScrollStateChanged(AbsListView view, int scrollState) {
}
#Override
public void onScroll(AbsListView view, int firstVisibleItem,
int visibleItemCount, int totalItemCount) {
if(mLastFirstVisibleItem<firstVisibleItem) /* DOWN */
{
scrolling = false;
}
if(mLastFirstVisibleItem>firstVisibleItem) /* UP*/
{
scrolling = true;
}
mLastFirstVisibleItem=firstVisibleItem;
}
});

Parallel listviews should scroll together when any one listview scrolls in Android

I am having two listviews in parallel on single screen. Both are having their own scroll listener.
What I want to do is scroll the first listview, then the second listview should also scroll and vice versa.
Is this possible ?

Suppose your ListViews are mListView1 and mListView2, then do something like this -
mListView1.setOnScrollListener(new OnScrollListener() {
#Override
public void onScrollStateChanged(AbsListView view, int scrollState) {}
#Override
public void onScroll(AbsListView view, int firstVisibleItem,
int visibleItemCount, int totalItemCount) {
// Smooth scroll mListView2 according to mListView1.
mListView2.smoothScrollToPosition(firstVisibleItem);
}
#Override
private void isScrollCompleted() {}
});

GridView onScrollPositionChanged?

I have a GridView and I want to change somthing, while the user scrolls, when it reaches a certain position. I know we have the onScroll() method of OnScrollListener, but in the reference it says:
This will be called after the scroll has completed
Is there a proper way to do this?
Thanks in advance for any help.

According to your goal, it seems that onScrollStateChanged(AbsListView view, int scrollState) method should do what you want.
Then, using getScrollY method of your GridView should allow you to check what position are you curretly at.
mList.setOnScrollListener(new OnScrollListener() {
#Override
public void onScrollStateChanged(AbsListView view, int scrollState) {
int scrollPosition = view.getScrollY();
// doSomething(scrollPosition)
}
#Override
public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
}
});

Realign Listview after scrolling/fling

I am trying to get a ListView to realign after every scroll/fling. By realign I mean realign in such a way, that the top item of the ListView is aligned with the top of the ListView, if it is cut off it should scroll down smoothly until it is realigned and fully visible.
I implemented a scroll-listener:
firstRowListView.setOnScrollListener(new OnScrollListener() {
private boolean correcting = false;
#Override
public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
}
#Override
public void onScrollStateChanged(AbsListView arg0, int scrollState) {
if (!correcting && scrollState == OnScrollListener.SCROLL_STATE_IDLE) {
correcting = true;
firstRowListView.smoothScrollToPosition(firstRowListView.getFirstVisiblePosition());
correcting = false;
}
}
}
});
(For easier visibility I only left the important bits in). If I scroll smoothly (no fling) it works fine, but if I fling the list it doesn't realign itself. Although LogCat tells me that the onScrollStateChange-method is executed in the same way as when I perform a "normal" scroll.
Why is this and how do I get the ListView to realign even after a Fling?

Following should work but on Galaxy tab 7 (4.0.4) I can see recursion happening. So I would strongly suggest that you implement some mechanism to avoid that otherwise this solution will break on some devices:
mylv.setOnScrollListener(new OnScrollListener() {
#Override
public void onScroll(AbsListView view, int firstVisibleItem,
int visibleItemCount, int totalItemCount) {
}
#Override
public void onScrollStateChanged(final AbsListView lv,
int scrollState) {
if (scrollState == OnScrollListener.SCROLL_STATE_IDLE) {
lv.post(new Runnable() {
#Override
public void run() {
lv.smoothScrollToPosition(lv
.getFirstVisiblePosition());
}
});
}
}
});

On older devices ListView does not report SCROLL_STATE_IDLE after SCROLL_STATE_TOUCH_SCROLL. Please use workaround mentioned here . http://code.google.com/p/android/issues/detail?id=5086#c7
You can also remove correcting variable safely, as it is of no use in this code.

How to keep listview showing the bottom items as I scroll an endless list?

I am having this trouble when developing an endless listview..As I scroll down to the bottom I fetch more data and update the listview, however it goes back to the top of the list. What else to I need to make the list load new item but not changing the position? Please help, Thx!
streamLV.setOnScrollListener(new OnScrollListener() {
#Override
public void onScrollStateChanged(AbsListView view, int scrollState) {
}
#Override
public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
boolean loadMore = firstVisibleItem + visibleItemCount >= totalItemCount;
if(loadMore){
dosomething to get the items..then
lvAdapter.addItem(item);
}
streamLV.setAdapter(lvAdapter);
}
}
});

Try calling lvAdapter.notifyDatasetChanged() instead of setting it again on the ListView (instead of calling streamLV.setAdapter()).