向活动添加片段

Question

First of all, I read everything here. https://developer.android.com/guide/components/fragments.html

I have one activity and I want to divide the screen horizontally and add 2 fragments. I know how to add fragments on XML but I don't want that. I want to add them on Java.

So the problem is FragmentManager doesnt work unless my activity extends Fragment. Should I do that on the activity or should I add fragment transaction methods on one of the fragments?

If I extend my activity to Fragment, does it also become a fragment?

If I put the fragmentmanager and fragmenttransaction on one of the fragments how can I make the connection with activity?

this is the activity which I want my fragments displayed on

import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

public class ConversionActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_conversion);

        NumpadFragment fragment = new NumpadFragment();
        FragmentManager fragmentManager = getFragmentManager();
        FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
        fragmentTransaction.add(R.id.numpad_layout,fragment);
        fragmentTransaction.commit();

    }
}

and this is one of the fragments

import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

public class NumpadFragment extends Fragment {
    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        return inflater.inflate(R.layout.fragment_numpad,container,false);
    }
}

Answer 1

Some suggestions:

• Use fragmentTransaction.replace (unless you need your fragments to be added to stack)
• As containter for your fragment, use FrameLayout
• Don't create new fragment by "new" operator. Add newInstance() method instead and create new fragment instance by calling that methrod. Also, implement interaction between your fragment and activity. Tip: use Android Studio wizard to add fragment to your project. Android Studio will generate skeleton with all needed methods already included
• You definitely need to use getSupportFragmentManager (because your fragment is android.support.v4.app.Fragment )
• DEBUG! - if you say "my app is crashing", it's useless. Post your logcat/exception/whatever to show crash reason.