I have a ViewPager, that i'm populating with fragments which has a listview inside. The point is that i have to show a really big amount of data, and i need to make pages, so i only request littel amounts of data.
My problem is that i need to call an asynctask to retrieve the data when the page is changed, and fill the listview of this page, how can i do this? How can i change that listview in the onPostExecute of the task?
PS: i have used an eclipse template for tabs + swipe activity, so im not posting my code.
I'm not sure I got your problem right, but the first thing that comes to my mind, is that I would use an AsyncTaskLoader instead of a simple AsyncTask. From my (limited) experience, loaders solve a lot of problems when it comes to Fragment/Activity lifecycle/configuration changes.
Loaders guide (Android Developers)
No matter what method you are using to get the data, changing the content of the list view in page B after loading the data in page A shouldn't be much of a problem: you have plenty of options, from simply saving the data for page B in the Activity (then changing the page with setCurrentItem and intercepting the page change event with setOnPageChangeListener),
to a more elegant approach employing a SQLite database (which btw would allow you to do some caching on the results, if possible).
Oh, and let's not forget that, if you are using an implementation of the abstract class FragmentPagerAdapter you can probably pass the data directly from one page to the other, as this PagerAdapter implementation
represents each page as a Fragment that is persistently kept in the fragment manager as long as the user can return to the page.
(just use getItem(int) to get a reference to the page you need. I never tried this myself, though).
Hope this helps
EDIT I just found out that getting a reference to the current Fragment shown in the ViewPager is tricky if you are not using a FragmentPagerAdapter: if this was the root of your problem, information about how it can be done can be found here:
Update data in ListFragment as part of ViewPager
Retrieve a Fragment from a ViewPager
Communication between ViewPager and current Fragment
Related
using firebase-ui and some coding I have set up my code to work like this:
1) it retrieves data from firebase (image, text and so on), then it passes them to another activity.
2) the new activity receives datas like strings and shows them.
Just to give you an idea I am looking forward to building a streaming app. What I want to do is to show an episode list via recyclerview.
What I am doing right now is a nested scroll view and a copy-paste script to pass up to 26 episodes, but this is not a really good method and I would like to have some suggestions in order to go forward in the best way and solve this problem.
this is a screenshot of the app: https://imgur.com/a/vgBnZTA I am just passing strings to the 2nd activity, then i check if it is not a null string, if it is i hide the layout, otherwise it shows, but it is just a copypaste of code. I hope i was clear enough
Thanks everyone for your support
I need to show one thousands question with 4 options to fill using one activity. I got an idea to use viewpager, but cant able to show 1000 fragment.
It is possible to use ViewPager with 1000 fragments. Just make sure that your adapter extends FragmentStatePagerAdapter.
From the documentation:
This version of the pager is more useful when there are a large number
of pages, working more like a list view. When pages are not visible to
the user, their entire fragment may be destroyed, only keeping the
saved state of that fragment. This allows the pager to hold on to much
less memory associated with each visited page as compared to
FragmentPagerAdapter at the cost of potentially more overhead when
switching between pages.
I have a Android app that shows lots of real-time data jammed onto one large scrolling activity.
Now i want to split it up into two simpler screens using fragments, where only one fragment may be on the screen at any one time.
I read up a whole lot on fragments and watched several videos, but before i start ripping up my code to convert it to fragments i wanted to know the following.
If i create two fragments A and B, then while showing fragment B, data comes in for fragment A. Can the controlling activity still communicate with fragment A giving it data even though its off screen? OR do i have to save the data somewhere and then when the user switches to fragment A then I give fragment A the data to be shown, while saving incoming data for fragment B which will now be off screen?
The problem is that right now im not saving any data because everything is on one screen, so as data come in i just displayed it, but if i switch to using fragments i dont know if i can do the same thing by passing the data to the fragments even if they are not on screen at the same time.
Thanks.
If you retrieve your data with multiple asynchronous requests in your Activity, you may create a fragment for each of them and move related retrieval operation into that fragment (probably to oncreateView() method). Then, you can use ViewPager (probably with TabLayout) in the parent Activity to be able to use all those fragments. Therefore, your Activity only deals with setting the ViewPager and leave the rest to fragments.
ViewPager shows one page at a time but it can initialize other fragments as well, even before they are shown. You can use ViewPager's setOffscreenPageLimit() method to increase that range.
In case you need a communication channel between fragments and the activity, you may create callback mechanisms, as described here.
Basically what the title says. I'm trying to start a ViewPager activity when a user clicks a RecyclerView item. I'm not having problems here, that works fine. The goal is to go from a grid based gallery to viewpager gallery. I'm also trying to send the List<> of data which is loaded over the network. This is where I'm having a lot of trouble. The data is sent through a singleton because it's too large to send through intent and if opened in the new activity too quickly upon app startup, more data is loaded in the original activity (Even if Call is cancelled, using Retrofit2 btw) and I need to notify the adapter, which I have a listener that does.
Another crash that is common is a null pointer when reading an item in viewpager activity, which doesn't make sense to me because the item is not null in the original activity before sending, but if I wait a few seconds it is not null. Some of the code pertaining to my issue can be found here, a question I asked yesterday with a solution I could not successfully implement.
Please point me in the right direction for starting a ViewPager of the same dataset from a RecyclerView, thanks
When you are "sending" feed data to the view pager activity, use a shallow copy of the list instead of directly referencing it as shown below
DataTransferer.get().storeItems(new ArrayList(feed));
This should prevent IllegalStateException raised by feed being updated on your RecyclerView activity.
Has anybody had any luck with a view pager switching between fragments that contain listviews? In particular, the listviews I am working with inflate two separate layouts to get the desired effect. However, to my understanding this is causing the viewpager to disappear as well as the tabhost. I believe this to be so because it is working with other fragments that only inflate once.
Edit 1:
I was trying to see what would happen if I used one of the fragments that showed the tabhost and used the viewpager first. I would switch views and see the correct next one. However, shortly thereafter one of the fragments that does not show the tabhost or use the viewpager, for some odd reason, would load up.
Edit 2:
It's weird it is not even loading up on the right page. It should load up on 3 but instead it loads up on 2 and replaces the former screen that was actually supposed to be there.
Adding listviews to two fragments is very easy.
In short, you want to have a main activity that's the viewpager itself. Next, the viewpager is going to host two tabs (can be as many as you want, really) which will both contain separate layouts...each with a listview of its own.
Code
The first thing we need to do is add some classes. I've made a GitHub Gist of 4 classes that I'd like you to implement into your project. You'll need to change the package name and R class to meet your project's needs.
Gist: https://gist.github.com/Andrew-Quebe/b3e9f1d0f8223ba2f8df
Second, we need to make our host activity. This is what will show the tabs and toolbar. See this next Gist as I don't want to spam up this answer with tons of code.
Gist: https://gist.github.com/Andrew-Quebe/8add2fc064397ab8efe4
You've probably gotten an error in the MainActivity.java file due to a missing ViewPagerAdapter class. That's up next!
Gist: https://gist.github.com/Andrew-Quebe/fd70ee97c2e00d72f025
And finally, the tabs that'll show our listviews!
Gist: https://gist.github.com/Andrew-Quebe/3e2a87706c98a69e7353
My apologies for taking so long in my response...I actually took the time to build all this code and error check it for you. I had an example of tabs once before but it was outdated...you weren't the only reason I made all this code. The full project can be found on GitHub here: https://github.com/Andrew-Quebe/SlidingTabsExample
Hope this helps!
Edit:
Download the sample APK to see how everything looks: https://github.com/AMQTech/SlidingTabsExample/blob/master/APKs/Sample.apk?raw=true
First of all I would like to apologize. I pointed you all in the wrong way. I did some research and as it turns out you cannot have the fragment container (frame layout) in the activity layout already. All I had to do was put the fragment container into a different layout and inflate it when the time came to switch to another fragment class and that fixed it. Thanks to everyone.