I'm developing an app that has an UI pretty similar to Play Store. It is organized as a multiple panels one above another. First it has a panel containing a photo. Under that it has another panel containing some text and a custom background color. Under that it has another photo and finally it has a Linear Layout with vertical orientation containing a pretty long list of little views filled dynamically at runtime. I have all this inside a Scroll View, naturally.
The problem? That dynamic fill of the linear layout takes a long processor time and makes my app unresponsive during those inner views inflation. So I thought to replace the linear layout by a Recycler View. And the performance is awesome!
So? Well... Not everything is so awesome. I can't scroll the Recycler View because it's inside the Scroll View. And if I remove the Scroll View then I can't scroll the entire view (some things doesn't fit on the screen).
What's the best approach for fixing this?
It's not recommended to use a RecyclerView or ListView inside of a ScrollView precisely due to the double scrolling issues. RecyclerView is very robust and is prepared to receive headers, footers, etc. I see no reason why the entire layout could not be inside of a RecyclerView instead of a ScrollView
The ViewHolder implementation can include logic to inflate different layouts depending on what section should be next.
Pseudocode:
i.e.
if(currentAdapterItem == sectionA){
useLayoutA();
} else{
useLayoutB();
}
Just use a NestedScrollView instead of a normal ScrollView. It handles the nested scrolling quite well.
Related
Am trying to create a page with a scrollable list. Features would be a normal list to remove item by clicking on it. Number of items in that list are limited and added dynamically by user. You can consider a to do list as example. Now which would be a better approach to implement it? Recycler view with data bound to its adapter? Or the normal linear layout with items added as children at run time?
My current implementation is recycler view. But,I found it lagging and animations are not performing well. So a linear layout is auto animated by specifying it xml -- by setting animate layout changes to true.
FYI data is local and syncs in background.
Never use a LinearLayout for anything longer than a single screen. The whole point of ListView and RecyclerView is to efficiently reuse views instead of needing to hold things in memory when they're not visible. Maybe you can refine or reask your question so people can help you with whatever difficulty you're having with animations, rather than avoiding the issue.
I have a ScrollView that contains several other views and I would like for one of these views to be a grid of other views having the same layout (e.g. ImageView).
Since having one scrollable view inside another is not recommended, I would like this grid view not to be scrollable, otherwise I would have used GridView or RecyclerView.
Surely I can place the grid views inside one of the standard layouts (e.g. TableLayout) but this may cause memory issues when many grid items exist.
Is there any standard approach or a library that allows to recycle views for a non scrollbale view inside ScrollView?
If you try to force GridView or RecyclerView to be non-scrollable (so basically you would have to force the dimensions of the view to display all the elements) you will end up in the same situation as if you used TableLayout (so you would need to watch out for memory issues).
If you disable the scrolling of scrollable (recycling) elements like GridView/RecyclerView you disable the most important part that makes those things work efficiently (that makes those things reuse their views).
The way you should solve your issue is to implement your other Views of your ScrollView as a part of the RecyclerView. Your RecyclerView should be equipped with the adapter that can inflate multiple types of Views (you can read about it for example here).
Since you are using RecyclerView you could use NestedScrollView instead of ScrollView They should play more nicely since RecyclerView extends from NestedScrollingChild and NestedScrollView extends from NestedScrollingParent.
Other views you can use are VerticalGridView or HorizontalGridView but as you said you are worried about performance issues and you can provide a GridLayoutManager to the RecyclerView I would stick with that.
I have an activity which shows these three things in order.
ViewFlipper (User can fling it left/right)
EditText
ListView (List view can have n number of rows. lets limit it for 100. each row has images which get downloaded asynchronously)
I want that user can scroll vertically so I put above three item in single relative layout and that in to scrollView
<RelativeLayout>
<ScrollView>
<RelativeLayout>
</RelativeLayout>
</ScrollView>
</RelativeLayout>
Problem with this approach
ListView and scroll view together is bad user-experience. When List will cover all screen user will have problem in scrolling complete view itself.
Solution which I could think of
Disable Scroll on ListView and let it show all items (Is this good enough)
User addHeaderView (not sure how to use it)
Second Approach (Which I did and ran into problems).
Instead of using ListView add LinearLayout (replacement of listrow) dynamically.
Problem with this approach
Lot of ugly coding as there is no sophisticated adapter for such scenarios. Need to populate each LinearLayout and it creates more issue because I have async Image loading for every LinearLayout.
What could be better approach. Any alternates?
Do not use a ScrollView and a ListView together, this is a bad thing as mentioned by Romain Guy, the creator of ListView. The problem with you LinearLayout approach is performance: you will need to create n new Views, while the ListView just reuses existing ones.
The solution I could think of (in case it is not possible to make your Layout components to fit on the screen without scrolling), you could disable scrolling in your ListView and add "scroll up" and "scroll down" buttons, setting the onClickListener and OnLongClickListener to let the user control scrolling speed. Though this might be not the best approach. Consider re-disigning your layout so the components fit on a single screen. This is usually not a good user expierince to enable scrolling because of layout components not fitting on a single screen. Your could add a page more to your ViewFlipper and place your ListView there for example
I'm researching creating a view for displaying EPG data. That is the view should:
have a fixed header column that shows the services,
have a fixed header row that shows the time and
a content area that has equal-height TextViews of flexible width for showing the actual EPG entries
Most importantly, scolling vertically must scroll header column as well, scrolling horizontally must scroll header row.
Apart from drawing the whole view myself (inside a scrollable?) I'm totally stumped if there is any good approach I could use involving linear layouts or such.
Any hints are greatly appreciated- please note that I'm and android beginner.
Approach 1: Everything (that is all views) are pre-generated.
Have top and left one-way ScrollViews together with a bidirectional ScrollView and have the scolling be synchronized ( Android: Synchronized scrolling of two different views ). Synchronized scrolling isn't to difficult to do if you've subclassing the ScrollViews and add your own ScrollManager to handle notifications.
Drawback: ScrollViews inside ScrollViews for the main content area do seem to be the desired option. The whole thing will become highly resource intensive as all items need to be created upfront to be available for scrolling.
Approach 1 takes care of view-synchronization for the scrolling, but is a huge resource hog (imagine an EPG with 30+ channels and 100+ events per channel).
Approach 2
One approach for this I could imagine would be- for the main content area- a ListView with a custom ArrayAdapter. Custom adapter would probably return a LinearLayout or similar holding the individual events. That way, scrolling would still work bidirectionally if the ListView is put into horizontal ScrollView and at least the LinearLayouts themselves could be recycled by the ListView.
Are there better approaches?
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.