Develop Reference

android scrollview scroll to top direction when new view added

In scrollview, if I add any view in middle, normally all the views below the added view scrolls downside. But I want to scroll the top views of added view to upside without disturbing the bottom views. Is it possible in scrollview , please help me ?
In the figure , If view 4 was added , then view 1 has to be scrolled upwards , without changing the positions of view 2 and view 3.

You can probably get the height of the view you are adding with and then scroll the scrollview manually that many pixels
scrollView.scrollBy(0, viewAdded.getHeight())

I've been wanting to try this question for quite some time, I finally got the chance today. The method is pretty simple (in fact, #dweebo already mentioned it earlier) - we move the ScrollView up as we add the view. For getting precise (and valid) dimensions when adding, we use a ViewTreeObserver. Here's the code you can get hints from:
// Getting reference to ScrollView
final ScrollView scrollView = (ScrollView) findViewById(R.id.scrollView);
// Assuming a LinearLayout container within ScrollView
final LinearLayout parent = (LinearLayout) findViewById(R.id.parent);
// The child we are adding
final View view = new View(ScaleActivity.this);
LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, 100);
view.setLayoutParams(params);
// Finally, adding the child
parent.addView(view, 2); // at index 2
// This is what we need for the dimensions when adding
ViewTreeObserver viewTreeObserver = parent.getViewTreeObserver();
viewTreeObserver.addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
#Override
public boolean onPreDraw() {
parent.getViewTreeObserver().removeOnPreDrawListener(this);
scrollView.scrollBy(0, view.getHeight());
// For smooth scrolling, run below line instead
// scrollView.smoothScrollBy(0, view.getHeight())
return false;
}
});

Check whether a RecyclerView needs to scroll

I have a callback that is fired after a programmatic scroll to a certain item of a RecyclerView via LinearLayoutManager.smoothScrollToPosition(). The user taps on an item and the right item is scrolled to the top of the RecyclerView. I subclassed LinearLayoutManager to have it always snap to the top of the item.
This works in case the scroll event is fired, but when the RecyclerView is already in the right position, I don't get the onScrollStateChanged callback, as no scrolling occurs. Is there a way to get that event anyway? Like decide beforehand whether or not the RecyclerView needs to scroll or not?

Hope the following code would help
if(LinearLayoutManager.findFirstCompletelyVisibleItem() == yourDesiredPosition) {
//do your stuff
} else {
LinearLayoutManager.scrollToPositionWithOffset(yourDesiredPosition, offset);
//onScrollStateChanged would be trigger then.
}

I found the following solution myself:
// get the view the user selected
View view = mLayoutManager.findViewByPosition(index);
// get top offset
int offset = view.getTop();
if (offset == 0) { // the view is at the top of the scrollview
showDetailViewInternal(event);
} else {
// scrolling
}

Programmatically add items to scrollview top, but should not scroll to top

I have scrollview with child LinearLayout . I am adding data programmaticaly to it. When i add some data to top of linearlayout it automatically scrolls to top element. But i want something like , user reaches top -> scrolls upside to load previous data ->add data to linearlayout top but should not get focus, after addition complete , if user scrolls then and then only it should display .
How to achieve this?

Well I thought of a way and it works almost perfectly.
I have a LinearLayout (llCommunicationsLayout) inside a ScrollView (svCommunications) .
I inflate a new LinearLayout, I'm going to add views to the top of this new LinearLayout and then add this new layout to the LinearLayout inside the ScrollView.
This is the new layout:
final LinearLayout wrapperLayout = (LinearLayout) mInflater.inflate(R.layout.empty_layout, null);
I add my views to the 0'th position of this layout.
wrapperLayout.addView(view, 0);
After all the views are added into the wrapperLayout, I add the wrapperLayout into the llCommunicationsLayout (the one inside my ScrollView)
llCommunicationsLayout.addView(wrapperLayout, 0);
After this, I calculate their heights after the wrapperLayout is on screen (has a measurable height)
wrapperLayout.post(new Runnable() {
#Override
public void run() {
int wrapperHeight = wrapperLayout.getHeight();
int svHeight = svCommunications.getHeight();
int scrollHeight = Math.abs(svHeight - wrapperHeight);
DisplayMetrics displaymetrics = new DisplayMetrics();
getWindowManager().getDefaultDisplay().getMetrics(displaymetrics);
int displayHeight = displaymetrics.heightPixels / 4;
svCommunications.scrollTo(0, (scrollHeight + displayHeight));
}
});
Here, I get both the newly added layout's and the ScrollView's heights.
I calculate their difference, add the 1/4 of the height of the screen of my device and scroll it, voila!
It's not perfect, but after the layouts are added, it no longer scrolls to the top of the screen. Experiment with the displayHeight for different results.
Hope this helps someone out.

You can grab the current view which is on top of your LinearLayout then add new content to your LinearLayout and then scroll back to view which was previously on top. The code would be something like:
public void addViewsOnTop(List<View> views) {
final View currentViewOnTop = (linearLayout.getChildCount() > 0) ? linearLayout.getChildAt(0) : null;
// Add Views. Note that views will appear in reverse order
for(View view : views) {
linearLayout.addView(view, 0);
}
// Scroll back to view which was on top
if(currentViewOnTop != null) {
new Handler().post(new Runnable() {
#Override
public void run() {
scrollView.scrollTo(0, currentViewOnTop.getBottom());
}
});
}
}

Solved....
Try this, worked for me ,
lv_chat.setAdapter(adapter);
lv_chat.setSelection(somePreviousPosition);

How to check whether a view is visible in specific area or not inside ScrollView

I have one ScrollView inside my application, this ScrollView contains number of images in it, we have to scroll up to the bottom to view each and every image because the area of scrollview is more than the screen size.
Now the question is that how can I check that each image of ScrollView is inside a specific area(defined by me) or not.
If the image is inside that area I want to do something and if its not then I want to do something different.
Please help me to get out of the problem, any help would be appreciable.
Thanks.

See below code, Check is this working
public static boolean isInVisible(ScrollView scrollView, View view, Rect region, boolean relative)
{
int top = scrollView.getScrollY() + region.top;
int bottom = scrollView.getScrollY() + region.bottom;
if(!relative)
{
// If given region is not relative to scrollView
// i.e 0,0 does not point to first child left and top
top -= scrollView.getTop();
bottom -= scrollView.getTop();
}
Rect rect = new Rect(region);
rect.top = top;
rect.bottom = bottom;
Rect childRegion = new Rect(view.getLeft(), view.getTop(), view.getRight(), view.getBottom());
return Rect.intersects(childRegion, region);
}

yes each imageinside the ScrollView is defined by you.so,you change any modifications inside yhe scroll view.if you have any specific need then post your code

Android ViewFlipper + homescreen animation

I am trying to use a ViewFlipper and make it act like the home screen(The layout will move with your finger). Check out this for an example. I want to do this with a ViewFlipper that only contains two children so the opposite view should be shown on either side of the current view depending on which way the user moves their finger. This code works but only for 1 direction at a time. This is in onTouchEvent.
case MotionEvent.ACTION_MOVE:
leftView.setVisibility(View.VISIBLE);
rightView.setVisibility(View.VISIBLE);
// move the current view to the left or right.
currentView.layout((int) (touchEvent.getX() - oldTouchValue),
currentView.getTop(),
(int) (touchEvent.getX() - oldTouchValue) + 320,
currentView.getBottom());
// place this view just left of the currentView
leftView.layout(currentView.getLeft() - 320, leftView.getTop(),
currentView.getLeft(), leftView.getBottom());
// place this view just right of the currentView
rightView.layout(currentView.getRight(), rightView.getTop(),
currentView.getRight() + 320, rightView.getBottom());
Which ever of the bottom two lines I put last that direction will work correctly but the other will not.
Here is how I set the leftView and rightView:
final View currentView = myFlipper.getCurrentView();
final View leftView, rightView;
if (currentView == meView) {
Log.d("current layout: ", "me");
leftView = youView;
rightView = youView;
} else if (currentView == youView) {
Log.d("current layout: ", "you");
leftView = meView;
rightView = meView;
} else {
leftView = null;
rightView = null;
}
Is it going to be possible to set it up so that the same view is shown on both sides of the current view?

Thanks stealthcopter
That worked here is the new code if anyone is interested.
if (touchEvent.getX() < oldTouchValue){
// place this view just right of the currentView
rightView.layout(currentView.getRight(), rightView.getTop(),
currentView.getRight() + 320, rightView.getBottom());
}else if (touchEvent.getX() > oldTouchValue) {
// place this view just left of the currentView
leftView.layout(currentView.getLeft() - 320, leftView.getTop(),
currentView.getLeft(), leftView.getBottom());
}
I also moved the setVisibility() calls to the MotionEvent.ACTION_DOWN in an attempt to get rid of some flickering of the views. This helped but I still get a bit.

I have possibly not very constructive suggestion, but if you want it to behave like a home screen, why you don't want to look at the src of that, and modify it to your needs ?

To get rid of the flickering, set setVisibility(View.INVISIBLE) in MotionEvent.ACTION_DOWN. The default value is "GONE" on a view. That means that you can not set Layout() on a view until it's either "VISIBLE" or "INVISIBLE". So in three steps:
Set Visibility to INVISIBLE on the View
Set Layout() on the View
Set Visibility to Visible on the View

If I understand your request, this effect should now be implemented using a View Pager
Looks like this: