How can I write a method with a fragment class as an argument that will allow me to create a new instance of that fragment?

Question

The Goal

I'm trying to write a method that would replace the code that I use to swap fragments in order to keep copying and posting to a minimum (and to stay D.R.Y.)

The Problem

I get an error when I attempt to use the class that I passed in as an argument to create a new instance of that class.

The error occurs in this line of code, to the left of the operator (equal sign):

newFragmentClass new_fragment = newFragmentClass.newInstance();     

The error it gives me is: "newFragmentClass cannot be resolved to a type".

Full Code

    private void changeFragment(Class<?> newFragmentClass)
    {
        // Detect the current fragment
            Fragment current_fragment = getSupportFragmentManager().findFragmentById(R.id.fragment_container);
    
        // Create a new instance of the given class, edit later to gracefully handle errors
            newFragmentClass new_fragment = newFragmentClass.newInstance(); 
            
        // Switch to the new fragment
            FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
            transaction.detach(current_fragment);
            transaction.replace(R.id.fragment_container, new_fragment);
            transaction.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE);
            transaction.commit();
            
        // Change the tab background to indicate that the tab is active, reset backgrounds for any other tabs
            findViewById(R.id.page_one_tab).setBackgroundResource(R.drawable.menu_button_background_active);
            findViewById(R.id.page_two_tab).setBackgroundResource(R.drawable.menu_button_background);
            findViewById(R.id.page_three_tab).setBackgroundResource(R.drawable.menu_button_background);
    
    }
    
    // Page One Tab Button Functionality
    public void pageOneTab (View v)
    {
        // Change the fragment to SelectPlayersFragment
        changeFragment(Page_One_Fragment.class);
    }

Attempted Solutions

I've been searching StackOverflow and the internet at large for quite a while and have not been able to find a solution. A few topics like this one seemed as if they would resolve the problem, but then I ran into an error on the transaction.replace line that I could not find a fix for: "The method replace(int, Fragment) in the type FragmentTransaction is not applicable for the arguments (int, Object)".

Answer 1

You probably want something like:

private Fragment changeFragment(Class<? extends Fragment> newFragmentClass)  {
    Fragment current_fragment = getSupportFragmentManager().findFragmentById(R.id.fragment_container);
    // Create a new instance of the given class, edit later to gracefully handle errors
    Fragment new_fragment = null;
    try {
         new_fragment = newFragmentClass.newInstance();
    } catch (InstantiationException e) {            
        throw new RuntimeException(e); // for some reason this fragment loading has failed so crash
    } catch (IllegalAccessException e) {            
        throw new RuntimeException(e);
    } 
    FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
    transaction.detach(current_fragment);
    transaction.replace(R.id.fragment_container, new_fragment);
    // ...   

Answer 2

Perhaps a more simpler solution would be to pass a Fragment as argument, instead of aClass, and use it to replace the current fragment. Also, you don't need to detach the current fragment, that is what replace() does for you.

Something like this:

public void changeFragment(Fragment fragment) {
    FragmentManager manager = getSupportFragmentManager();
    FragmentTransaction transaction = manager.beginTransaction();
    transaction.replace(R.id.fragment_container, fragment, "tag");
    transaction.commit();
    //.....
}

And you use it like this:

changeFragment(new Page_One_Fragment());

Answer 3

I think you want this:

private <T extends Fragment> void changeFragment(Class<T> newFragmentClass)
{
    ...
    // Create a new instance of the given class, edit later to gracefully handle errors
    T new_fragment = newFragmentClass.newInstance(); 
    ...
}

Answer 4

Because your "newFragmentClass' is only a parameter of method, it's not a type so you can not instance it. Follow my code to fix your problem

private <T extends Fragment> void changeFragment(Class<T> newFragmentClass)
    {
        // Detect the current fragment
            Fragment current_fragment = getSupportFragmentManager().findFragmentById(R.id.content);

        // Create a new instance of the given class, edit later to gracefully handle errors
            T new_fragment = newFragmentClass.newInstance(); 

        // Switch to the player select fragment
            FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
            transaction.detach(current_fragment);
            transaction.replace(R.id.fragment_container, new_fragment);
            transaction.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE);
            transaction.commit();

        // Change the tab background to indicate that the tab is active, reset backgrounds for any other tabs
            findViewById(R.id.page_one_tab).setBackgroundResource(R.drawable.menu_button_background_active);
            findViewById(R.id.page_two_tab).setBackgroundResource(R.drawable.menu_button_background);
            findViewById(R.id.page_three_tab).setBackgroundResource(R.drawable.menu_button_background);

    }