I know this question has been asked many times, and I have looked everyone of them here but none of which helped me.
What I am trying to do is to mimic the UI from iOS where you have a UITableView with cells that are UICollectionView. The cells are images that page horizontally. I am trying to do this with a listview of viewpagers.
My current solution is I create each row before hand. It is a linearlayout with a title, the viewpager, and two buttons on the bottom. I already created the adapters for the viewpagers as well. In the getView method of listview, I just return the view in the created collection based on the position as the index. I know this is bad practice, it uses a lot of memory, but the method is just one line.
I have tried the viewholder pattern, but only some rows in the listview will get the viewpager. The recycling mechanism doesn't really help in my situation, so I sacrifice more memory for the same effect.
So I can see all the viewpagers in my listview. The problem now is that only the bottom 2 are able to page from iamge to image. The ones on position 0,1,2, couldn't. I thought it has to do with listview intercepting the events, but how come the ones on the bottom work perfectly??
Any help is appreciated!
Related
I'm making sort of a news feed, that is displayed below a static menu. To avoid the news feed from being scrolled in the tiny bit of space that's left after the menu, I wanted to scroll both the menu and the newsfeed at the same time.
Now I'm realizing this with a LinearLayout, so it doesn't scroll itself like the listview. But my question is, is using a LinearLayout, which from what I know doesn't reuse views like a listView, bad practice? How likely am I to get into memory issues, since the news feed can have A LOT of views, and they all contain images.
Many thanks!
Apparently there is a pretty good chance for you to get an OutOfmemmoryexception in no time with this approach,If you want to go with re-using the views
I suggest you should go with the new RecyclerViews in Android,
Go here for a tutorial on recycler views
I don't know if this qualifies to be an answer. But if you are using a LinearLayout with a header view and a ListView inside it, then there are no issues. Since the main worry you have is the news feed which would be recycled by the ListView. Neglecting to use view recycling is asking for trouble, and will likely break after 50 or so (Android hates images).
As for the header that must disappear. I would avoid putting it as the first item in a ListView as suggested in the comments, and rather have it static in the LinearLayout. And use a view translation and/or transparency to hide it. This keeps the option availible to display the header at any point, regardless of the list's scroll.
Everyone knows that GridView does not supports headers and footers like a ListView.
There is a few ways to implementing this:
Use a ListView and form columnt manually via ViewGroups. It not works for me, because it's require a lot of layout operations like measuring and layouting, and it's difficult to implement draw selector on top.
Use special adapter. It works fine with a footer: we should fill last cells with a Space and manually insert after them out footer with width that equals GridView width. But this not works with headers: although header is stretched, next cells float on it.
Use a GridLayout. GridLayout is good, but what about performance with 500-1000 cells? AdapterView supports caching and reusing Views, as far as I know, this is not possible with GridLayout.
Extend GridView and write custom class, that allows to draw a header before the grid content. It's difficult, but it's should work very fast. Let's try to figure out how to do this:
Measure the header. It's very simple, I have not questions about this.
Layout header in the top of the grid. We also should consider with scrolling position to allow move header with whole grid content, so my first question is: how to know where bottom border should be located while scrolling?
Layout whole grid content after the header. How to do that? I've newer do this before.
Dispatch draw to the header view too and resolve overscrolling effect if it's not work well.
Handle the scroll event and refresh header position.
So what you can suggest me? How to do header offset? Is it right to invoke relayouting with every scroll event?
I searched an answer on a same situation with a GridView (but for a FooterView).
I've read attentively your suggestions and some from other websites. I had the same reflexion. I found a simple way as your tip: "Use special adapter. It works fine with a footer..." and this answer by #RaulSoto helped me a lot. But when I tried to update my gridview, I had a NPE, because my footer was not like the layout of my items and I had a custom filter which recalculated the getCount() method, but without understand that another view was added.
Finally, I found only solution which works: a custom class.
Create your own class as you said: "Extend GridView and write custom class" but don't extend GridView. You should extend with ListView and measure the entire width, the column width and the number of columns. I think, it's less difficult that to extend GridView, calculate the height of the header view and move it as you move your gridview or refresh the header each time you handle a scroll event..
I searched to do it in this way and I took this little project on GitHub: HFGridView by Sergey Burish. It was exactly what I need, no more.
I only added a custom attrs file in my app and customize a bit his project to have the expected result (especially, it was to have one column in portrait, two in landscape mode, refering to the numColumns attribute in my layout).
And when I try, just for test, to add a HeaderView and refresh the content with adding new items, the header view stays at the top of my gridview list, without refreshing himself.
So, I think you should search to create your class as GridView extends ListView. Refer you to the HFGridView by SBurish, it is very simple to understand how it does.
Hope this helps you with your purpose.
Photos in this layout can be swiped left and right, and swipe should be 'intelligent', like switching between photos and NOT like just horizontal scrolling of photos.
2 implementations that come to my mind:
HorizontalScrollView (but swiping is dumb)
ViewPager (but there is no way to see adjacent photos)
So, basicly I need a ViewPager for photos that can show adjacent photos.
Is there a robust solution for this?
For cool swiping action viewpager is the best. And you won't have problems with memory. BUT I have no idea how to make view pager part of listview.
If you have final number of items you can use Android Gallery widget which is deprecated since api 16 but does exactly what you need, the main problem is that it cant reuse gallery items inside the adapter.
You also can try this:
Horizontal list view
I have used TwoWayView to implement my layout.
It's better than HorizontalView, cause it re-uses views (like ListView).
I have an app which loads a boatload of images and displays them in a TableLayout which is inside a ScrollView. At run time I get the width of the layout parent and use that to determine how many images can go in each TableRow (all of the images are of a set size).
I'm concerned about memory issues when loading more and more images. I know ListView recycles its views but I don't know how to dynamically change number of views in each item. I am only aware of inflating XML which isn't going to change the number of views per item at run time.
So my question is what is easier - figuring out how to recycle views in my table by myself, or making a list's items change based on screen size? Just a link to a tutorial on how to do whichever is easier is good enough an answer for me.
I suggest you to use ListView with the ViewHolder approach (you can see it here: How to load the Listview "smoothly" in android).
The ListView, when scrolled, removes the views that are no more visible and gets the views that are about to become visible. This way, it's better than using a ScrollView and a TableLayout.
I've been stuck with this situation for few days now. My problem is I've multiple gallery views and I want to make the scrolling of all the gallery views synchronized. So if one gallery view is scrolled I need to scroll all the other gallery Views in my layout at the same time and the entire view should seem like it's one coherent view getting scrolled and not multiple views.
I've to use multiple gallery views and using a horizontalScrollView or anything else doesn't seem to be a good option in my case.
I found a similar question here:
Synchronize two Galleries but there are no solutions.
Right now I'm out of ideas and any pointers will be helpful