I was just reading few stackoverflow threads about scrolling views larger than parents. Everywhere is used ScrollView or HorizontalScrollView for this, but what is puzzling me is why does every single view have methods and xml attributes for setting scrolling? For example, Im currently overriding method onScrollChanged() of View class. I mean can every view have a scrollbar?
Because View is a class/Object.
To give you a more to the point example here you go:
public class Test extends View {
}
Therefor, it's pretty much obvious for View to have methods for each instance of the object.Right?
Related
I'm currently trying to design a ViewGroup (specifically a subclass of FrameLayout) that can layout any number of subviews and enable them for drag/drop outside the layout group. It's almost identical to a LinearLayout:
Curently I am able to drag the views outside the ViewGroup and draw them, however after letting go of the view it can't be re-selected and further dragged around.
I'm wondering if there is a way to do this in a way that isolates the logic to the Layout subclass and doesn't involve needing to do much/any extra stuff in consuming fragments/view groups.
I've tried overriding getHitRect(Rect) in my FrameLayout subclass but it never seems to be called. dispatchTouchEvent(MotionEvent) is of course not called either, presumably because the parent ViewGroup has decided not to deliver the touch to it because it was outside the bounds. I've tried implementing a TouchDelegate as well, but I think that needs to be set on the parent view, which means needing to know about this and doing this additional step when using this Layout.
Any ideas on if/how this is possible? On iOS it can be implemented fairly easily by overriding hitTest: to take into account the frames of the child views. Is there a similar method like this on Android?
Your help is greatly appreciated!
Without any code it is very hard to see what you are doing, but best guess would be that each view should a child view of the relative layout.
I have a horizontal RecyclerView inside a NestedScrollView inside a SwipeRefreshLayout. Presumably this is a cause for error. When I load the data the children display fine but once I scroll to an end and rescroll the children aren't filling their views.
In action
I've found a bunch of different advice on how to fix this with layout constraints, different parent view types, and changing focus but the problem still occurs. onBindViewHolder is definitely getting called but for some reason the binding doesn't happen?
This strange happened because of recycling process for the recycler view, all layout code written at the bind view (in the View holder) will ignored on recycling, and to solve it, add this code:
RecyclerView.setRecyclerListener(new RecyclerView.RecyclerListener() {
#Override
public void onViewRecycled(RecyclerView.ViewHolder holder) {
((BusinessChildViewHolder) holder).onBind();
// onBind method inside your holder and it just applies the layout changes that you need
}
});
Found the issue: In my viewholder I set certain layouts as invisible and since the views are recycled they weren't showing. All I had to do was set them to visible.
From this solution https://stackoverflow.com/a/29325270/6136947
I have been working with Android for about 4 months. I need some guidance on how to implement something like this:
In that picture I've used three of the custom viewGroups (calling it ArcScrollView) stacked on top of on another which is what I am trying to achieve.
The questions that I have are:
Do I need to extend ViewGroup, frameLayout or what?
How can I make it scrollable?
I took a look at LinearLayout source code and it was extending frameLayout but again LinearLayout is not scrollable and need to be hosted by a scrollView.
I need to have complete control over scrolling because these arcScrollView are rectangles and I need onTouchIntercept of the viewGroup to return false (not consuming) at certain positions.
Is scrolling actually just changing the starting position of the first child view and putting them after one another or something magical that Android does?
I think I need to override the onDraw method also for drawing the partial circle. Does that effect anything that I need to worry about?
Should I override the ScrollView and LinearLayout instead? because I think there is a lot that have been implemented in them.
I am trying to draw a View in a ViewGroup without adding it to the child list.
I am doing this because I want to display something like a ProgressBar in the exact center of layouts like a LinearLayout so I don't want the layout to handle the measuring and layouting.
I also don't want to complicate the view hierarchy by adding extra layouts just to achieve this effect so my solution was to extend the LinearLayout, create a ProgressBar and handle measuring, layouting and drawing for that view myself.
My implementation seems to work ok from what I tested but I am wondering if there is anything I am not noticing or if there are any problems that can appear in the future.
From what I understand calling addView also sets the child view's parent and calls dispatchAttachedToWindow, these methods are package-private so I can't call them myself.
Is there any side effect that can arise from calling measure, layout and draw on a view that has no parent and that was not "attached" to a window? Is there a safer way to achieve the same effect?
Thanks.
I have extended LinearLayout (vertical) to create a custom compound component. This in turn contains two children:
one custom view that is drawn directly onto the view canvas.
one HorizontalScrollView->LinearView(Horizontal)->Multiple custom views.
I would now like to redraw the custom view to match the visible contents of the scroll view. The reason for this is that the long array of custom components in the scroll view are mainly static and suitable to be drawn ahead of time, while the top view is supposed to be highly dynamic and relate to whatever things are visible in the scroll view.
I hope I made the problem/idea somewhat clear. I am not att all confident this is the best approach, and I'd enjoy hearing any suggestions on alternative solutions or perhaps some idea on how to trigger a redraw-event everytime the scroll position changes in the HorizontalScrollView.
Thank!
You can have your activity listen to the scroll view adapter. in the adapter when ever the scroll position changes you execute the delegate in the Activity.
That way the activity can update the rest of the views upon scroll view change.