package example.hfad.fragments_chapter7;

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

public class WorkoutDetailFragment extends Fragment {
    private long workoutId;

    public WorkoutDetailFragment() {
        // Required empty public constructor
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        return inflater.inflate(R.layout.fragment_workout_detail, container, false);
    }

    public void setWorkout(long id){
        this.workoutId = id;
    }
}

package example.hfad.fragments_chapter7;
import android.app.Activity;
import android.os.Bundle;

public class MainActivity extends Activity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        WorkoutDetailFragment frag = (WorkoutDetailFragment) getFragmentManager().findFragmentById(R.id.detail_frag);
    frag.setWorkout(1);

    }
}

WorkoutDetailFragment frag = (WorkoutDetailFragment) getFragmentManager().findFragmentById(R.id.detail_frag);

WorkoutDetailFragment frag = (WorkoutDetailFragment) getSupportFragmentManager().findFragmentById(R.id.detail_frag);

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
  WorkoutDetailFragment frag = (WorkoutDetailFragment) getSupportFragmentManager().findFragmentById(R.id.detail_frag);
  frag.setWorkout(1);
}