Develop Reference

scrollBy doesn't work properly in nested recyclerview

I have a vertically scrolling RecyclerView with horizontally scrolling inner RecyclerViews just like this.
With this implementation, users can scroll each horizontal recyclerview synchronously. However, when a user scroll vertically to the parent recyclerView, a new horizontal recyclerview which has just attached on window doesn't display on same scroll x position. This is normal. Because it has just created.
So, I had tried to scroll to the scrolled position before it was displayed. Just like this:
Note: this is in adapter of the parent recyclerview whose orientation is vertical.
#Override
public void onViewAttachedToWindow(RecyclerView.ViewHolder holder) {
super.onViewAttachedToWindow(holder);
CellColumnViewHolder viewHolder = (CellColumnViewHolder) holder;
if (m_nXPosition != 0) {
// this doesn't work properly
viewHolder.m_jRecyclerView.scrollBy(m_nXPosition, 0);
}
}
As you can see, scrollBy doesn't effect for row 10, row 11, row 12 and row 13 After that, I debugged the code to be able find out find out what's happening. When I set scroll position using scrollBy, childCount() return zero for row 10, row 11, row 12 and row 13 So they don't scroll. But why ? and Why others work ?
How can I fix this ?
Is onViewAttachedToWindow right place to scroll new attached recyclervViews ?
Note: I have also test scrollToPosition(), it doesn't get any problem like this. But I can't use it at my case. Because users can scroll to the any x position which may not the exact position. So I need to set scroll position using x value instead of the position.
Edit: You can check The source code

I found a solution that is use scrollToPositionWithOffset method instead using scrollBy. Even if both of two scroll another position, they have really different work process in back side.
For example: if you try to use scrollBy to scroll any pixel position and your recyclerView had not been set any adapter which means there is no any data to display and so it has no any items yet, then scrollBy doesn't work. RecyclerView uses its layoutManager's scrollBy method. So in my case, I am using LinearLayoutManager to the horizontal recyclerViews.
Lets see what it's doing :
int scrollBy(int dy, RecyclerView.Recycler recycler, RecyclerView.State state) {
if (getChildCount() == 0 || dy == 0) {
return 0;
}
mLayoutState.mRecycle = true;
ensureLayoutState();
final int layoutDirection = dy > 0 ? LayoutState.LAYOUT_END : LayoutState.LAYOUT_START;
final int absDy = Math.abs(dy);
updateLayoutState(layoutDirection, absDy, true, state);
final int consumed = mLayoutState.mScrollingOffset
+ fill(recycler, mLayoutState, state, false);
if (consumed < 0) {
if (DEBUG) {
Log.d(TAG, "Don't have any more elements to scroll");
}
return 0;
}
final int scrolled = absDy > consumed ? layoutDirection * consumed : dy;
mOrientationHelper.offsetChildren(-scrolled);
if (DEBUG) {
Log.d(TAG, "scroll req: " + dy + " scrolled: " + scrolled);
}
mLayoutState.mLastScrollDelta = scrolled;
return scrolled;
}
As you can see scrollBy ignores the scroll intentions if there is no any child at that time.
if (getChildCount() == 0 || dy == 0) {
return 0;
}
On the other hand scrollToPosition can work perfectly even if there is no any set data yet.
According to the Pro RecyclerView slide, the below sample works perfectly. However you can not do that with scrollBy.
void onCreate(SavedInstanceState state) {
....
mRecyclerView.scrollToPosition(selectedPosition);
mRecyclerView.setAdapter(myAdapter);
}
As a result, I have changed little thing to use scrollToPositionWithOffset().
Before this implementation I was calculating the exact scroll x position as a pixel.
After that, when the scroll came idle state, calculating the first complete visible position to the first parameter of the scrollToPositionWithOffset().
For second parameter which is the offset, I am getting the value using view.getLeft() function which helps to get left position of this view relative to its parent.
And it works perfectly!!

Compare Drawables on ImageViews

I'm trying to create a One-armed Bandit app.
I have created an animation xml file to go through multiple images. When a button is clicked, the animation stops.
My question is how to compare the picture that one animation stopped on with that of another? So far I've tried something like this:
if(wheel1.getBackground().getConstantState().equals(wheel2.getBackground().getConstantState())) matches++;
Any help is appreciated.

you must be starting the animation with .animationStart()
just use .onAnimationStop() and it will trigger the event automatically.

A View should not maintain application logic, the controller (your hosting Activity or Fragment) should.
That said, to achieve what you want use View.setTag() to apply a logical description of each View to it.
Then when stopping animation, loop through all Views you have and get their position on screen, get the Views mostly visible in each column of your bandit machine and compare their tags (View.getTag())
for example, if the items animate vertically use below method to determine where the bandit stopped.
//the area where to compare views
int BOUND_TOP, BOUNT_DOWN;
//your content view
ViewGroup rootLayout;
//method to get information about what is visible
public List<Object> getVisibleViewTags() {
List<Object> list = new LinkedList<>();
int count = rootLayout.getChildCount();
for (int pos = 0; pos < count; pos++) {
View child = rootLayout.getChildAt(pos);
float translationY = child.getTranslationY();
if (translationY > BOUND_TOP && translationY < BOUND_DOWN) {
list.add(child.getTag());
}
}
return list;
}
Now you just need to attach information about a view as tag to it.
example:
view.setTag("view_apples");
or
view.setTag("view_bananas");

Find out only completely visible list items in android- list view

I want to find out the position or ids related to a ListView's items: only those ones which are completely visible on the screen.
Using listview.getFirstVisibleposition and listview.getLastVisibleposition takes partial list items into account.

I followed a little bit similar approach as suggested by Rich, to suit my requirement which was to fetch completely visible items on screen when List View is scrolled every time.
This is what i did
public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
//Loop to get tids of all completely visible List View's item scrolled on screen
for (int listItemIndex = 0; listItemIndex <= getListView().getLastVisiblePosition() - getListView().getFirstVisiblePosition(); listItemIndex++) {
View listItem = getListView().getChildAt(listItemIndex);
TextView tvNewPostLabel = (TextView) listItem.findViewById(R.id.tvNewPostLabel);
if (tvNewPostLabel != null && tvNewPostLabel.getVisibility() == View.VISIBLE) {
int listTid = (int) tvNewPostLabel.getTag();
if (listItem.getBottom() < getListView().getHeight()) {//If List View's item is not partially visible
listItemTids.add(listTid);
}
}
}
}

I have not tried this, but here are the pieces of the framework that I believe will get you to what you're looking for (at least this is what I'd try first)
As you've stated, you should get the last visible position from the list view using ListView.getLastVisiblePosition()
You can then access the View representing this position using ListView.getChildAt(position)
You now have a reference to the view, which you can call a combination of View.getLocationOnScreen(location) and View.getHeight()
Also call View.getLocationOnScreen(location) and View.getHeight() on the ListView. y + height of the View should be less than or equal to y + height of the ListView if it is fully visible.

How to detect when any child view recieves a click

Given an arbitrary ViewGroup G with an arbitrary collection of child views, how can I detect when the user clicks on any of the child views? In this case, I want to draw a highlight for G.
I could add an onClick listener for each child, but I'm trying to avoid that so that the code doesn't have to be changed when the layouts change.
Alternatively, I could add onTouch handlers to G and set the highlight during ACTION_DOWN. However, this would trigger for actions that don't actually result in clicks, such as a swipe (the swipe could be handled by ViewPager, for example, and ultimately be irrelevant to G).
My layout for G has the focusable attributes:
android:focusable="true"
android:focusableInTouchMode="true"
Thanks.

Here is how I do it:
//in onTouch method of parent, I get the coordinates of click
int x = ((int) motionEvent.getX());
int y = ((int) motionEvent.getY());
//obtain the clickable arrea of the child as HitRect
Rect clickRect = new Rect();
Rect rect = new Rect();
imageView.getHitRect(rect);
//ask if the area contains the coordinates of the click
if(rect.contains(x, y)){
//do some work like if onClickListener on the child was called.
return false; //you clicked here, don't need to handle other Childs
}
//ask for other childs like before...
Now, you can target the parent as the delegate of all clicks done inside it, even if it is done in a child.
EDIT:
To ignore other touch event that are not click, you can ask for how much user moved the finger:
case MotionEvent.ACTION_MOVE:
case MotionEvent.ACTION_CANCEL:
if (Math.abs(motionEvent.getRawX() - initialTouchX) > 5 || Math.abs(motionEvent.getRawY() - initialTouchY) > 5) {
return true; // user mover finger too much, ignore touch
}
return false; // finger still there waiting for click
I give a square of 10 pixels to permit a confortable click, and if you exit it, I ignore it.
EXTRA:
Here is the complete code for click and long click with onTouchListener.

You could use the View.getChildCount() to loop through all child views and see if the touch intersects with the child view.
This involves getting x and y positions and calculating if it fits within the child view, use View.getChildAt(position) to get the reference to the child view .
So it would be something like this:
int childNr = theView.getChildCount();
for (int i = 0; i < childNr; i++){
YourView tmp = (YourView) theView.getChildAt(i);
if(tmp.intersects(x, y)){
do some work
}
}
here you would have to put your view variable instead of theView and the class name which handles the views instead of (YourView) and x, y are the coordinates of the pressed spot.

In your XML, you could add point all the children to the same onClick method. Inside that method you could draw the highlight to G and then do something (or nothing) for the individual child view.

Commonsware Drag Drop shrinks row height permanently

I did get the drag and drop working and the TouchListView class works great. However in my case I have rows of various height due to my adapter which contains an EditText that can have multiple lines. Therefore after I drop, all my rows convert to the tlv:normal_height which in my case is 74dip. This causes many rows to cut off all my text in the EditTexts. I tried re initializing my adapter (mylistview.setAdapter= myadapter), setting the ListView to GONE then VISIBLE and invalidateViews() but nothing seems to reset the ListView back to before I dragged, short of leaving the activity and coming back. What can be done here? -Thx
tlv:normal_height="74dip"
tlv:expanded_height="128dip"

There's little question that the original AOSP code was designed for uniform row heights, and the whole expanded_height construct was there to provide space for the user to visualize where the drop would occur.
One starting point would probably be to create a TouchListAdapter mixin interface (akin to SpinnerAdapter) where the normal_height and expanded_height would be retrieved dynamically from the adapter based on position as opposed to being fixed values declared in the layout. Whether that alone would be sufficient or more work would need to be done, I can't say.
If you come up with a solution, patches are welcome. Otherwise, I'll probably take a look at this sometime, but not very soon.
My apologies for not having a near-term silver bullet.

I edited the unExpandViews() method - called getAdapter() and for every item in my adapter set the height to 0 and then all the rows were set back to original. I also bypassed the delete part of the method since it did not apply to me.
private void unExpandViews(boolean deletion) {
int height_saved = 0;
CheckBoxifiedTextListAdapter cbla = (CheckBoxifiedTextListAdapter)getAdapter();
for (int i = 0;i < cbla.getCount(); i++)
{
//View v = getChildAt(i);
View v = cbla.getView(i, null, null);
//if (v == null)
//{
/*
if (deletion)
{
// HACK force update of mItemCount
int position = getFirstVisiblePosition();
int y = getChildAt(0).getTop();
setAdapter(getAdapter());
setSelectionFromTop(position, y);
// end hack
}
layoutChildren(); // force children to be recreated where needed
v = getChildAt(i);
if (v == null)
{
break;
}
height_saved = v.getHeight();
*/
//}
//else
//height_saved = v.getHeight();
if (isDraggableRow(v))
{
ViewGroup.LayoutParams params = v.getLayoutParams();
params.height = 0;
v.setLayoutParams(params);
v.setVisibility(View.VISIBLE);
}
}
}