CODEWITHSUNDEEP
javaandroidgenericsandroid-fragments
Viktor Valencia
Viktor Valencia

Reputation: 435

How to make an Interface with Generic type and inheritance of Android Fragment?

I'm developing an Android project with an Activity and some Fragments. The idea is: When the activity is launched it shows the Fragment A, and when the user click on Fragment A button, the activity should replace the Fragment A, whit a new instance of Fragment B, I would like to make the fragments completly independent of the host Activity, as a modular fragments.

So I wanna to implement a simple interface that help me to change the current fragment on the activity to another. In the interface I have create a single method that could manage a FragmentTransaction for any object type inheritance of Fragment class, but I'm little lost with this issue, I have searched and read much documentation but I couldn't get a clear answer about this. I not sure how to do it. I have some code but it's incorrect or incomplete

Here is my interface for my Fragment A:

public interface ActivityInterface {
    void replaceFragment(int fragmentId, <? extends Fragment> fragment);
}

this would be the Activity implementation:

public class MyActivity  implements ActivityInterface {

    public void  replaceFragment(int fragmentId, <? extends Fragment> fragment) {
        FragmentTransaction fragmentTransaction = getFragmentManager().beginTransaction();
        fragmentTransaction.replace(fragmentId, fragment);
        fragmentTransaction.commit();
    }

}

I am a novice in 'Java Generics' topic so please be clear, I'd appreciate a lot.

Upvotes: 2

Views: 1632

Answers (1)

EpicPandaForce
EpicPandaForce

Reputation: 81539

I believe you are looking for this:

public interface ActivityInterface {
    <T extends Fragment> void replaceFragment(int fragmentId, T fragment);
}

public class MyActivity  implements ActivityInterface {

    public <T extends Fragment> void replaceFragment(int fragmentId, T fragment) {
        FragmentTransaction fragmentTransaction = getFragmentManager().beginTransaction();
        fragmentTransaction.replace(fragmentId, fragment);
        fragmentTransaction.commit();
    }
}

(although technically I think that'd work just fine with merely void replaceFragment(int fragmentId, Fragment fragment);)

Upvotes: 1

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