Develop Reference

Smooth Scroll Not Working on Initial Scroll for Android RecyclerView

I am working on an Android app that runs on only one devicerunning KitKat.
The smooth scrolling feature for a RecylerView I used that was working on other physical tablets and genymotion has unfortunately stopped working on the one device it needs to work on.
Instead of scrolling to a certain position it passes over the target position and scrolls all the way to the bottom and looks really bad.
I am able to track down the error to the abstract SmoothScroller in the RecyclerView class.
if (getChildPosition(mTargetView) == mTargetPosition) {
onTargetFound(mTargetView, recyclerView.mState, mRecyclingAction);
mRecyclingAction.runIfNecessary(recyclerView);
stop();
} else {
Log.e(TAG, "Passed over target position while smooth scrolling.");
mTargetView = null;
}
I was using a SnappingLinearLayoutManager that I found online, but swapped it out with the normal LinearLayoutManager from Android, and still am having the same problem.
The list is 7 items long (user can see 4 at a time) and I scroll to the 5th item (position 4) item.
When I scroll to the 3rd I don't receive this error.
Also after I scroll the list up and down once, the error stops happening.
EDIT:
I am able to use layoutManager.scrollToPositionWithOffset(); But I am trying to do this with the smooth scroll animation.
Here is some of my code and details:
private void setupMainRecyclerViewWithAdapter() {
mainLayoutManager = new SnappingLinearLayoutManager(this, LinearLayoutManager.VERTICAL, false);
mainListRecyclerView.setLayoutManager(mainLayoutManager);
settingsMainListAdapter = new SettingsListAdapter(SettingsActivity.this,
settingsPresenter.getSettingsItems(),
settingsPresenter);
mainListRecyclerView.setAdapter(settingsMainListAdapter);
mainListRecyclerView.addItemDecoration(new BottomOffsetDecoration(EXTRA_VERTICAL_SCROLLING_SPACE));
}
#Override
public void scrollMainList(boolean listAtTop) {
if(listAtTop) {
mainListRecyclerView.smoothScrollToPosition(4);
moveMainMoreButtonAboveList();
} else {
mainListRecyclerView.smoothScrollToPosition(0);
moveMainMoreButtonBelowList();
}
}

If you call recyclerView.smoothScrollToPosition(pos) will be called immediately on the UI thread and if recyclerView's Adapter is too much busy to generating view items then the calling of smoothScrollToPosition will be missed then because recyclerView has no data to smooth scroll. So it's better to do that in a background thread by recyclerView.post(). By calling this it goes into the Main thread queue and gets executed after the other pending tasks are finished.
Therefore you should do something like this which worked for my case:
recyclerView.post(new Runnable() {
#Override
public void run() {
recyclerView.smoothScrollToPosition(pos);
}
});

Well, I realize it's too late, however I tried some different solutions and found one...
in custom LinearSmoothScroller I override updateActionForInterimTarget
#Override
protected void updateActionForInterimTarget(Action action) {
action.jumpTo(position);
}
It's appears not very smooth, but not instant in contrast with scrollToPositionWithOffset.

Just add one line for smooth scroll
recyclerView.setNestedScrollingEnabled(false);
it will work fine

Take a look at hasPendingAdapterUpdates(). You can use this along with a delay() for coroutines or Thread.sleep() to enable the backing data to be available before doing the scroll.

How to make a ViewFlipper behave like a Scroller?

Good day everyone.
I am creating a calendar component, and I'm working in the month view. I have created a view named MonthView, and I am adding a couple instances of this to a ViewFlipper:
viewFlipper = new ViewFlipper(getContext());
viewFlipper.addView(new MonthView(viewFlipper.getContext()));
viewFlipper.addView(new MonthView(viewFlipper.getContext()));
I have implemented the fling gesture so that I change views when sliding my finger left or right. This will cyclically update and display the months.
Now, I need to give the fling gesture a smoothly effect when touching and slowly sliding my finger. The same we get when we use a Slider instead a ViewFlipper.
The problem with Scroller is that the effect is not cyclic. Once I get to the last view, I have to slide in the other direction.
I need someone help me find how to give a scroll-like effect to the ViewFlipper, or how to make a Scroller cyclic.
Thanks in advance.
Extra comment:
I have already implemented a ViewFlipper with 2 views. I update the views by using the SimpleOnGestureListener.onFling(...) method, and the behavior I got is something like this:
Imagine I always slide from rigth to left, like flipping a book's page to read the next one, and also imagine there is a caption in the header of the view that is displayed after flipping.
View # 0 --> Caption: January 2011
View # 1 --> Caption: Febrary 2011
View # 0 --> Caption: March 2011
View # 1 --> Caption: April 2011
View # 0 --> Caption: May 2011
If at this point I slide from left to right, the result will be something like:
View # 1 --> Caption: April 2011
View # 0 --> Caption: March 2011
The ability to cyclically move forward or backward, giving the user the idea of having infinite views, but using only a couple is characteristic of ViewFlipper, and that's what I can't loose.
That's why I need a way to add the cool scroll effect without loosing what I've got.
Thanks.

Then you can use ViewFlinger!
viewflinger this an android widget (extends ViewGroup) that allows to group a set of views that can be swiped horizontally. It offers a smoother transition that cannot be accomplished using ViewFlipper. This is based on the Workspace class on the iosched project, which is based in the class with the same name of the Launcher app.
Download: 1.0.2 | Sources | JavaDoc
If you use Maven, you can use it as an artifact from this repository: http://mvn.egoclean.com/. Also, you would want to look this video where I show how it looks like: http://www.youtube.com/watch?v=gqIXq5x7iLs (sorry for my accent which sucks)

I think what you wanted to do is create an apparently infinite list of layouts being flinged by either the ViewFlipper or Christian's ViewFlinger. And also you want to keep reusing views / layouts inside the Flinger / Flipper. Right ?
If yes, probably the following is what you wanted to do. I've done this based on Christian's ViewFlinger,
Here you go,
First add three layouts to the ViewFlinger:
<com.egoclean.android.widget.flinger.ViewFlinger
android:id="#+id/calendarViewFlipper"
android:layout_width="fill_parent"
android:layout_height="fill_parent" >
<ScrollView
android:id="#+id/calendarViewLayout0"
android:layout_width="fill_parent"
android:layout_height="fill_parent" >
</ScrollView>
<ScrollView
android:id="#+id/calendarViewLayout1"
android:layout_width="fill_parent"
android:layout_height="fill_parent" >
</ScrollView>
<ScrollView
android:id="#+id/calendarViewLayout2"
android:layout_width="fill_parent"
android:layout_height="fill_parent" >
</ScrollView>
</com.egoclean.android.widget.flinger.ViewFlinger>
Then inside your activity, you take an array of three views so that you can access them directly through the array instead of searching every time inside the flinger,
private ViewFlinger viewFlinger;
private ViewGroup layouts[] = new ViewGroup[3];
private boolean userEvent = false;
#Override
public final void onCreateSub(Bundle savedInstanceState)
{
setContentView(R.layout.your_layout);
viewFlinger = (ViewFlinger) findViewById(R.id.calendarViewFlipper);
layouts[0] = (ViewGroup) findViewById(R.id.calendarViewLayout0);
layouts[1] = (ViewGroup) findViewById(R.id.calendarViewLayout1);
layouts[2] = (ViewGroup) findViewById(R.id.calendarViewLayout2);
viewFlinger.setOnScreenChangeListener(new ViewFlinger.OnScreenChangeListener()
{
#Override
public void onScreenChanging(View newScreen, int newScreenIndex)
{
}
#Override
public void onScreenChanged(View newScreen, int newScreenIndex)
{
if (userEvent)
{
ViewGroup tempLayout = null;
if (newScreenIndex != 1)
{
// We don't want our actions to raise events and create a cyclic event chain
userEvent = false;
if (newScreenIndex == 2) // Scrolling towards right
{
tempLayout = layouts[0];
viewFlinger.removeViewFromFront();
viewFlinger.addViewToBack(tempLayout);
layouts[0] = layouts[1];
layouts[1] = layouts[2];
layouts[2] = tempLayout;
// Any other logic comes here...
}
else if (newScreenIndex == 0) // Scrolling towards left
{
tempLayout = layouts[2];
viewFlinger.removeViewFromBack();
viewFlinger.addViewToFront(tempLayout);
layouts[2] = layouts[1];
layouts[1] = layouts[0];
layouts[0] = tempLayout;
// Any other logic comes here...
}
// We switch the screen index back to 1 since the current screen index would change back to 1
viewFlinger.setCurrentScreenNow(1, false);
userEvent = true;
// And any other logic that you'd like to put when the swapping is complete May be fill the swapped view with the correct values based on its new location etc...
View result = refreshView(tempLayout.getChildAt(0));
if (result.getParent() != tempLayout)
{
((ViewGroup) result.getParent()).removeView(result);
tempLayout.removeAllViews();
tempLayout.addView(result);
}
}
}
}
});
}
I hope this is clear to you and helps you with your problem. It is working very fine for me! Should work fine for you too.
P.S. Thanks # Christian for the ViewFlinger, it is awesome. However it lacks some good onConfigurationChanged logic, if you get time do put something in :). The rest is the best !

Stop ListView scroll animation

I have a ListView with about 100 entries. When the user does the "fling" from bottom to top it starts scrolling and keeps on scrolling even when the finger does not touch the display any more.
Is there a way to stop the scrolling animation at this point?

and we lookup the android source code (AbsListView), give it a ACTION_CANCEL touchEvent, can stop the fling. it is easy.
listView.dispatchTouchEvent(MotionEvent.obtain(SystemClock.uptimeMillis(), SystemClock.uptimeMillis(), MotionEvent.ACTION_CANCEL, 0, 0, 0));

I didn't try the solution of Pompe de velo but since smoothScrollToPosition() is not available for API level less than 8 this didnt work for me.
I agree, changing default behaviour is not a good Idea, but sometimes you need to. So here is my (dirty) solution which uses reflection. This is by far not the recommended way since it's a hack but it works for me. There might be a better solution but I didn't found it.
class StopListFling {
private static Field mFlingEndField = null;
private static Method mFlingEndMethod = null;
static {
try {
mFlingEndField = AbsListView.class.getDeclaredField("mFlingRunnable");
mFlingEndField.setAccessible(true);
mFlingEndMethod = mFlingEndField.getType().getDeclaredMethod("endFling");
mFlingEndMethod.setAccessible(true);
} catch (Exception e) {
mFlingEndMethod = null;
}
}
public static void stop(ListView list) {
if (mFlingEndMethod != null) {
try {
mFlingEndMethod.invoke(mFlingEndField.get(list));
} catch (Exception e) {
}
}
}
}

Well there surely is a way to do it. But the point is more whether or not it is advisable to do it, in my opinion.
The list is a standard Android control that behaves constistently across all applications. So I would be surprised if I found a list that did not behave the same in your application. You can stop the fling by putting your finger back on the screen at any time.
That said, if you want to do extra work, you could subclass the list view and override its on touch method. Best way to know what to do is to get the source code of ListView (ListView in Android 1.6).

You can prevent flinging for ListViews in API 8 by overriding onTouchEvent and calling smoothScrollBy.
#Override
public boolean onTouchEvent(MotionEvent ev) {
switch (ev.getAction()) {
case MotionEvent.ACTION_UP:
this.smoothScrollBy(0, 0);
break;
}
return super.onTouchEvent(ev);
}
This takes over from the fling scrolling and scrolls 0px instead.

My opinion is that you shouldn't modify this behaviour, since the fling behaviour is what the user expects.
However, to your question. I haven't tried this but in theory it should work.
Implement an OnScrollListener to your ListView and use the onScrollStateChanged() method to check if the current state is SCROLL_STATE_FLING. After you've determined that the scrolling perfoms by a fling you can get your ListView's first visible position by using the getFirstVisiblePosition() method and from there you can use smoothScrollToPosition() where you put in your getFirstVisiblePosition() value as an argument.

if you what disable default animation from list view just need set id for root (main) layout in xml and call void onClickListener in class for root layout

Android OnLongClickListener strange / unreliable behaviour

I'm currently fighting against the OnLongClickListener on Android Api Lvl 8.
Take this code:
this.webView.setOnLongClickListener(new OnLongClickListener() {
#Override
public boolean onLongClick(View v) {
System.out.println("long click");
return true;
}
});
It works perfectly. I can press anywhere on the WebView and the event triggers every time.
Now take a look at this one:
this.webView.setOnLongClickListener(new OnLongClickListener() {
#Override
public boolean onLongClick(View v) {
final EditText editText = getUrlTextField();
switch (editText.getVisibility()) {
case View.VISIBLE:
editText.setVisibility(View.GONE);
return true;
case View.GONE:
editText.setVisibility(View.VISIBLE);
return true;
default:
return false;
}
}
});
Assuming the URL EditText components is currently visible, it gets gone from the display and should be shown again when another long click event is triggered.
But if you run this, the event just works once (!) when one performs a long click on any position on the WebView. To make things complicated, the long click works again when it is performed on a link on the website...
Can anyone explain if it is a bug in the sdk and/or if there is a mistake in my thinking how the OnLongClickListener is working?!? :/
EDIT:
I've run now several different scenarios on a Nexus One and come to following conclussion: Changing the layout on runtime more or less kills the OnLongClickListener... I haven't found a way to get it work reliably at all...
I would really appreciate if anyone could give me a hint... I'm at my wits end :(

Personnally, I ended up by re-setting the listener after each relayout.

I've run into this issue as well. It seems that if the view layout changes in a way that child view bounds need to be modified (i.e. TextView is wrap_content width and you set its text to something longer/shorter than it was before), views in the hierarchy will have their onStartTemporaryDetach method called (most likely due to a layout pass, although I haven't dug deep enough to find out for sure). If you look at the source for View that onStartTemporaryDetach ultimately unsets the pressed state of the view.
Changing the views in your layout that will be updated periodically to have bounds that will not change regardless of the value you set, will fix the issue. Although, that is still not awesome.

android: AbsListView.OnScrollListener SCROLL_STATE_IDLE is not called after SCROLL_STATE_TOUCH_SCROLL (Version 2.1)

I have a problem with android version 2.1. It looks like a bug.
I attached an OnScrollListener to my listView.
I'm using the method onScrollStateChanged(AbsListView view, int scrollState) for monitoring the scroll's state of my listview.
The scrollstate could assume 3 value (taken from the documentation):
SCROLL_STATE_FLING: The user had
previously been scrolling using
touch and had performed a fling. The
animation is now coasting to a stop
SCROLL_STATE_IDLE:The view is not
scrolling. Note navigating the list
using the trackball counts as being
in the idle state since these
transitions are not animated.
SCROLL_STATE_TOUCH_SCROLL:The user
is scrolling using touch, and their
finger is still on the screen
I assume that the SCROLL_STATE_IDLE will always be passed after one of other two states.
It's always true excepted for android version 2.1.
SCROLL_STATE_IDLE is not passed after SCROLL_STATE_TOUCH_SCROLL
The problem happens also if you stop the fling by a touch instead of let the scroll stop by itself.
This strange behaviour leaves my listView in an unconsistate state.
Someonelse has the same problem?
Suggestion for a "not-so-dirty" work around?

I think there is a bug that has been registered for this case.
http://code.google.com/p/android/issues/detail?id=5086

I got a similar issue on 2.2.
If the list is big enough, and I scroll down up, I got first CROLL_STATE_TOUCH_SCROLL while my finger is on the screen. When my finger leave the screen I got the SCROLL_STATE_FLING. When my view has stopped moving I got the SCROLL_STATE_IDLE.
But, if during scroll, it reaches either View Top or Bottom, I only scroll/fling values and never the idle.
I checked out Shelves project from Romain Guy and his implementation suffer the same issue on 2.2.x I'm wondering if he had noticed yet.
I haven't tried yet with 2.3.x

I found something of a workaround for this (at least for API level 9+, where I'm still seeing the bug). I'm using a GridView, but I believe this should also work for ListView.
I'm using a subclass of GridView where I am detecting the overscroll (top or bottom):
public class CustomGridView {
private boolean mIsOverScrolled = false;
#Override
protected void onOverScrolled(int scrollX, int scrollY,
boolean clampedX, boolean clampedY) {
mIsOverScrolled = true;
super.onOverScrolled(scrollX, scrollY, clampedX, clampedY);
}
public boolean isOverScrolled() {
return mOsOverScrolled;
}
public void clearOverScroll() {
mIsOverScrolled = false;
}
}
Then, in my OnScrollListener of CustomGridView, I have:
#Override
public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount,
int totalItemCount) {
if (gridView.isOverScrolled()) {
gridView.clearOverScroll();
}
// ...
}
Now when I'm checking for OnScrollListener.SCROLL_STATE_IDLE, I also check if !gridView.isOverScrolled(). I'm not sure if that fixes your specific use cases, but hopefully you can use the additional piece of info to determine your current state despite the bug.

I have had this same problem and posted a workaround on the bug list mentioned by DeRagan:
Link