Fragment-Back-Stack

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

Purpose

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.

Usage

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();
fragmentStack.push(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
ft.hide(fragmentStack.lastElement());
//push the new fragment into stack
fragmentStack.push(resultListFragment);

![Second Fragment](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();
    fragmentStack.lastElement().onPause();
    ft.remove(fragmentStack.pop());
    fragmentStack.lastElement().onResume();
    ft.show(fragmentStack.lastElement());
    ft.commit();
} else {
    //if size is `1` it means first fragment is visible and we can exit from application
    super.onBackPressed();
}

MIT License

The MIT License (MIT)

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

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