I'm using FragmentPagerAdapter with a tabbed interface. My interface happens to have three tabs. I can see that as soon as my app is created, the adapter requests that both tabs one and two both be created immediately (I assume this is so swiping to the next tab appears smooth to the user).
Is there a way to stop the automatic loading of the next tab? My tabs are pretty heavy, and loading two right at startup is taking a good deal of time,
Thanks
Is there a way to stop the automatic loading of the next tab?
Sorry, no. This is driven by setOffscreenPageLimit(), and the minimum value is 1, meaning that ViewPager will always try to create and hold onto at least 1 page on each side.
It sounds like you need to move more logic into background threads.
Related
I am creating an app which will have multiple 'grids' containing a title and image thumbnails in each grid square.
Each Grid will have different content stored in it.
I have so far created one activity that initialises an instance of GridView, and uses a custom GridAdapter. (See photo for what it currently looks like) I was planning to swipe left to create a new empty grid in which the user can upload content. There may be anywhere up to 50 grids.
I'm just learning how to implement the gesture, and how to create a new instance of the activity, but from what I've read, I am thinking I have designed it badly.
I was planning for each grid to be an Activity (each takes up the full screen).
I envisaged an Activity as being like a Class in java that you can create instances from a blueprint. I thought if I created one 'Grid' I could create a new instance of it each time. Fragments didn't seem appropriate at the time, as the android tutorials often described them as being purposed to add components to activities.
I'm starting to think though that I am using the wrong methodology here and I need to change it? Can someone guide me in the right direction? I have written all the code already - if I need to change it, do Fragments and Activities share any methods, meaning I can retain some work?
Like you mentioned, using activities for holding content in your use case where switching may be triggered using gestures will definitely be resource heavy and cumbersome. Since, you mentioned swipe gestures, I believe fragments would be much lightweight in this situation. In fact, I would suggest you even look at ViewPager which even recycles fragments for you and optimizes user experience by loading the next fragment for a smoother experience. It will also handle swipe gestures for you!
[UPDATE]
Based on your updated explanation of the user flow, I'm certain that the ViewPager would fare as a better option mainly because it allows for a much better control and user navigation. It will also take care of handling swipe gestures and memory issues that come with these types of flows. Moreover, it will even allow for a page titles and bottom tab indicators in case you need them.
It will require each of its pages to be a fragment (your ViewPager will itself reside in an Activity). Once the user clicks on a grid cell, you can show a dialog window from where user input can be captured. This setup should be optimal for you resource wise in my opinion.
I have an scrollable tabs + swipe activity with 3 different fragments on it. It works well but I don't want my fragments to be destroyed when I navigate between them. For example, when I create the activity, it's shown the first fragment but it's created the second one too. When I swipe to the second fragment, the third is created, so I can swipe to the third one and it will be created before I open it. When I return to the second one, my third fragment still stays created but when I return to the first one, the third fragment is deleted.
There would be any way to avoid this? I don't want my fragments to be deleted when I navigate between them.
If you use a ViewPager, it has a method called setOffscreenPageLimit(int limit). Try and see if setting that higher works
This answer should help you figure out what's going on. Pretty much you are most likely using a FragmentStatePagerAdapter, when you should be using a FragmentPagerAdapter. That keeps it from deleting fragments not in view.
If, for performance reasons, you need to have the fragments deleted when they aren't being used, there are other options. Either look at why the performance is that bad when you have only 3 tabs (It shouldn't be unless you are doing something wrong with a listview, or have a map open, etc.) or you can code the fragments to save their state when they are being destroyed (which should be happening anyways with a FragmentStatePagerAdapter).
If that doesn't help, we'll need more info on what you are doing exactly to help.
I have created a tabbed android application using android.support.v4.view.PagerAdapter.
There are about seven tabs in the application and I plan to add more. Each tab contains a lot of controls (TextView, Spinners, Toggle buttons, Check boxes etc.)
On the first tab there is a drop down to select a profile. The user can 'Load' or 'Save' a profile he wants.
A profile contains data for all the controls in the tabs and I need to update the UI controls in all the tabs.
I have all the data loaded from the profile but the UI controls are not getting updated.
There is a 'UpdateUI' function which calls 'set' functions (setText, setChecked etc. for individual controls after finding its view by ID).
I was informed that only three tabs (Previous, Current and Next) are kept in memory so I wrote the application such that the 'UpdateUI' function is called to set UI data only when user swipes to that particular tab (figuring out the active fragment).
Using DDMS logs I saw that the data loaded was proper but the 'setText' or 'setXXXXX' function does not update the fragment tab.
I have also checked several possible issues:
Possibility of 'OnTextChanged' or an 'OnListener' updating the data again.
Made sure 'UpdateUI' is called from UI thread.
Using notify data change and redrawing UI to make sure UI is updated.
I am a novice Java/Android programmer. Please point me in the right direction.
viewpager.setOffscreenPageLimit(size);
you can instantiate all your fragments by setting limit then you can update all widgets inside other fragments.
If my understanding of Android Fragment management is right, once the fragment becomes invisible for user (say some other fragment completely overlayed it or in your case you change tabs) Fragment goes through onPause and possible onStop lifecycle stages, this mean it's kind of hybernated and can't be changed before it get's visible. viewpager.setOffsetPageLimit(size) tells the fragment manager (or rather pageAdapter) how many fragments should be kept hybernated, and I doubt it playing with this will change anything, but let me know if it's, because otherwise the solution may be more complicated.
What I'd do is recreate a fragment every time user gets to see it and pass your profile data to it's constructor (or following better practice newInstance() static method), it will in fact save memory since keeping many fragments there may be overwhelming. Alternatively you can check what profile is chosen everytime fragment is calling it's onResume, and update your controls there.
I want a Viewpager that shows loading while content is coming in from the background. Basically I expect the first View to be loaded, but View+1 and View-1 will still be loading. If the user swipes to either side I want them to be presented with a spinning dialog while it loads
Would I just add AsyncTasks into the ViewPager with some conditions determining when they will run? I dont want too many AsyncTasks to be loading as the viewpager will have many views off to the sides.
I think the Trulia app does this, it is similar to what I am looking for. Apartment image viewing shows a loading screen while the images are loading in that viewpage.
Also for the record, can I just treat viewpagers like onCreate functions of an activity? That would really clear things up
Insight appreciated
Have a look at the supplied FragmentPagerAdapter if you want to perform more Activity-like lifecycle management of each page.
I currently have a TabActivity which has 4 tabs, within one of the tab's I want to be able to move forward and back between 4 different Activities.
However if I try to start a new Activity now it removes the TabActivty and starts a whole new Activity with no tab bars.
I have read about using view groups but that this is not best practice and also about using a view flipper but this doesn't seem to let me switch between different Activities only change the views within the Activity. I can't implement back functionality for exa,ple.
Can anyone point me in the right direction as to what I should be looking for as a solution to this?
EDIT:
Some more information:
Within the TabActivity my first screen will be a ListView that contains 4 rows, then selecting one of these will in turn load another ListView with 2 rows again within the TabActivity and then the 3rd screen will just contain some text depending on which option the user chose again within the Tab Activity.
Is a ViewFlipper the best solution here? It seems to me that it will require a lot of coding within one Activity if I use the ViewFlipper?
I have done something similar. I used the ViewFlipper to achieve this. You can override onBackPressed in your Activity so you can deal with moving back through your views.
There's a couple of ways of doing this but a simple way would be to just increment a counter in your Activity as you move to the next views, then in your onBackPressed method if counter != 0 just show the previous view, if counter == 0 call super.onBackPressed.
You can see in my video showing what the result could look like (ignore the bug being shown in the video).