Thursday, 27 November 2014

Android Fragment Back Stack handling


Fragment Back Stack manager while displaying fragments on single activity and need to maintain on back press


We know that there is activity stack in Android. We don't need to maintain the stack while opening or closing activity. It will automatically handle the stack and show you the top of activity when you pressed back button.
But in fragment, its neccessary to handle them. Because Android is not going to handle them. We need to create a stack of fragment and manage them while pressing back button.
So, I have created one demo to represent how to handle the fragment in Back Stack.


In the sample application, you will find one object named fragmentStack. Its a Stack which will push and pop the fragment as per requirement.
Whenever you are displaying any new fragment, just push that fragment into stack using following code.

 //here this fragment is our first fragment  
 homeListFragment = new HomeListFragment();  


And when you are displaying any other fragment over this fragment, use following code.
We will create a new object of second fragment and add it to stack.

 //here this fragment is second fragment  
 resultListFragment = new ResultListFragment();  
 //hide the last fragment  
 //push the new fragment into stack  

Second Fragment.png

When backPressed event fires, we will check whether stack size is 2 or not. If it is, then we will pop last fragment and display the previous fragment by following code.

 if (fragmentStack.size() == 2) {  
   FragmentTransaction ft = fragmentManager.beginTransaction();  
 } else {  
   //if size is `1` it means first fragment is visible and we can exit from application  

Click here to download full source code