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ViewPager Fragment RecycleView Reset

I have 3 fragments in the ViewPager.
PersonalFragment
CropFragment
NotesFragment
Every fragment has a RecyclerView and I was adding items using a dialog in it. However, when I go to the last fragment (i.e. NoteFragment), the first fragment's (i.e. PersonalFragment) RecyclerView gets empty (all items are removed). The same thing happens when I come back to the first fragment, the last fragment's RecyclerView resets (all items are removed).

It is difficult to understand without seeing some of your code which is related. I think you might have implemented the onResume function incorrectly. Each time you go to the third fragment in your ViewPager, the first Fragment needs to be reinitialized and you need to take care of this in your onResume function.
However, another workaround for your problem is setting the off-screen page limit of the ViewPager like the following.
viewPager.setOffscreenPageLimit(2);
Hope that helps.

Android - viewpager fragments

Without me pasting any code, i have an activity that shows three fragments using a viewpager to swipe between them.
When the activity is created, tab one is showing.. If i select the second tab and go back to the first tab, everything is fine. But if i select the third tab and then select the first tab again, the onResume method is called within the first tab and its causing some undesirable results... why would onResume only be called when coming from the third tab and not the second? Its like tab one is being killed when you swipe to tab three, but tab one is not being killed if you just swipe to tab two..

Without seeing the code I can only guess, but when you use tab you are going to be using a FragmentPagerAdapter or FragmentPagerStateAdapter this keeps reference to the fragments that are kept alive. I'm going to guess that you are using the FragmentPagerStateAdapter which only keeps certain fragments alive and destroys other fragments when they leave the view. So that when you are on the 3rd fragment, the first fragment is being destroyed, which is recreated and thus calls onResume when you go back and visit it. When you are on the 2nd tab, the fragment isn't destroyed and so when you visit it, it does not need to call onResume. Fragments keep one fragment to the left and one to the right "alive" even though they are not in view. So when you are on 1, 2 is alive. When you are on 2, 1 & 3 are alive, when you are on 3, 2 is alive. I hope this helps.

To add more to BlackHat's answer,
You should use FragmentStatePagerAdapter, if you dont already, instead of FragmentPagerAdapter.
Also you should set the OffscreenPageLimit property of yoru view pager to the number of pages that should be retained to either side of the current page in the view hierarchy in an idle state.

Where should I code in Fragment that it will run only once- android

I am implementing Tab Layout with Swipeable Views in android. For implementation I had followed
AndroidHive
and
Tabs and swipe views.
But with both, I am facing the same problem. I am having 3 fragments but when my application run, onCreateView of 1st and 2nd Fragment called instead of only of 1st fragment's. When I swipe and go to 2nd fragment, onCreateView of 3rd Fragments get called.
So, whatever I code in 2nd fragment execute in the first fragment view. I researched and came to know that it happen to keep the next fragment into memory for smooth animation. But I am wondering, where I would code in the fragment so that it will execute only once or how to restrict Fragment getItem() method to be called only once. What can be the solution for this?

According to the Fragment's documentation you can implement the onCreate() link:
The system calls this when creating the fragment. Within your implementation, you should initialize essential components of the fragment that you want to retain when the fragment is paused or stopped, then resumed.
This should fix your problem, because i guess you now only use the onCreateView which might be called more than once.
For more information you can check the Fragment's lifecycle or documentation

FragmentStatePagerAdapter fails to load the fragments again when I get back to old instance of the parent Fragment

Scenario:
I have a fragment which has a ViewPager which contains 5 instances(different) of a single Fragment with different values, each having a listivew that contains some sort of items.
Problem:
The flow goes smooth when I click an item of listView(say on page1) but the moment I come back from there on pressing back (overridden OnBackPressed in the main_activity (will discuss later)), the viewPager fails to load the subFragments.
But when I switch to the 2nd or 3rd page, it gets displayed, and on going back to 1st page, it now gets displayed.
OnBackPressed():
I am maintaining a manual stack here. When I click on an item of ListView, the current Fragment Instance (of the parent Fragment ofcourse) goes into stack. And when user comes back , that instance gets popped off the stack and I replaces it on the activities FrameLayout container.
References:
Fragments not getting recreated by FragmentStatePagerAdapter after coming back to the main Fragment instance
Guys, I am really pissed off here, please help me out.

Frankly, I haven't worked much with fragments.
But it seems like the page is being thrown off the memory every time you switch to other pages. I am not sure but if there is a way for android to manage this and keep the page in its memory persistently, it might solve the problem

Finally I am able to get a workaround for this issue, which included two things:
while replacing the fragment make a call to
ft.replace(R.id.content_frame, frag).addToBackStack(null);
while initiating the ViewPager, the fragment manager to be used is :
mAdapter = new myAdapter(getChildFragmentManager());
Actually the problem is that, android fails to recognise and load the older instance of the fragment unless you explicitly add that instance to the backstack. So after adding it to BackStack, there is practically no need to maintain your own manual Stack, but you still can do that.

View pager with fragments - showing dialog onStart

I'm new in using view pager, I've done everything correctly, I conveted my activities into fragments and put them in FragmentPagerStateAdapter.
When testing it in the emulator, what I noticed is that the onCtreate to the onResume are called one fragment before the actual visibility on the view pager - it makes sense, the device wants to get ready for the next step, but the problem is that I have one fragment which calls a dialog every onStart so that actually happens on the wrong fragment.
What should be done?

You can use an OnPageChangeListener on your ViewPager to detect when you navigate to the right fragment.