ERROR: debe implementar OnFragmentInteractionListener

Es trowing un error diciendo que debo implment el OnFragmentInteractionListener, pero por lo que estoy enterado lo estoy aplicando correctamente … Cualquier ayuda sería apreciada grandemente.

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import android.app.Activity; import android.app.FragmentManager; import android.app.FragmentTransaction; import android.os.Bundle; public class MainActivity extends Activity implements NavFragment.OnFragmentInteractionListener, ContentFragment.OnFragmentInteractionListener{ @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); FragmentManager fragmentManager = getFragmentManager(); FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction(); fragmentTransaction.add(R.id.nav, new NavFragment()); fragmentTransaction.commit(); fragmentTransaction = fragmentManager.beginTransaction(); fragmentTransaction.add(R.id.content, new ContentFragment()); fragmentTransaction.commit(); } @Override public void onNavFragmentInteraction(String string) { Bundle args = new Bundle(); args.putString("string", string); ContentFragment content = new ContentFragment(); content.setArguments(args); FragmentManager fragmentManager = getFragmentManager(); FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction(); fragmentTransaction.addToBackStack(null); fragmentTransaction.commit(); } @Override public void onContentFragmentInteraction(String string){ } } 

NavFragment

 import android.app.Activity; import android.app.Fragment; import android.os.Bundle; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.widget.Button; import android.widget.EditText; public class NavFragment extends Fragment implements View.OnClickListener { private static final String ARG_PARAM1 = "param1"; private static final String ARG_PARAM2 = "param2"; private String mParam1; private String mParam2; private Button button; private OnFragmentInteractionListener mListener; public static NavFragment newInstance(String param1, String param2) { NavFragment fragment = new NavFragment(); Bundle args = new Bundle(); args.putString(ARG_PARAM1, param1); args.putString(ARG_PARAM2, param2); fragment.setArguments(args); return fragment; } public NavFragment() { } @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); if (getArguments() != null) { mParam1 = getArguments().getString(ARG_PARAM1); mParam2 = getArguments().getString(ARG_PARAM2); } } @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { View v = inflater.inflate(R.layout.fragment_nav, container, false); button = (Button) v.findViewById(R.id.submit); button.setOnClickListener(this); return v; } public void onButtonPressed(String string) { } @Override public void onAttach(Activity activity) { super.onAttach(activity); try { mListener = (OnFragmentInteractionListener) activity; } catch (ClassCastException e) { throw new ClassCastException(activity.toString() + " must implement OnFragmentInteractionListener"); } } @Override public void onDetach() { super.onDetach(); mListener = null; } @Override public void onClick(View v) { String string = ((EditText) v.findViewById(R.id.gridSize)).toString(); mListener.onNavFragmentInteraction(string); } public interface OnFragmentInteractionListener { public void onNavFragmentInteraction(String string); } } 

ContenidoFragmento

 import android.app.Activity; import android.app.Fragment; import android.net.Uri; import android.os.Bundle; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.widget.GridView; public class ContentFragment extends Fragment { private static final String ARG_PARAM1 = "param1"; private static final String ARG_PARAM2 = "param2"; private String mParam1; private String mParam2; private OnFragmentInteractionListener mListener; public static ContentFragment newInstance(String param1, String param2) { ContentFragment fragment = new ContentFragment(); Bundle args = new Bundle(); args.putString(ARG_PARAM1, param1); args.putString(ARG_PARAM2, param2); fragment.setArguments(args); return fragment; } public ContentFragment() { // Required empty public constructor } @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); if (getArguments() != null) { mParam1 = getArguments().getString(ARG_PARAM1); mParam2 = getArguments().getString(ARG_PARAM2); } } @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { View v = inflater.inflate(R.layout.fragment_content_fragmet, container, false); String string = "1"; if (getArguments() != null) { Bundle args = getArguments(); string = (String) args.get("string"); } GridView gridView = (GridView) v.findViewById(R.id.gridview); gridView.setNumColumns(Integer.parseInt(string)); gridView.setAdapter(new GridAdapter(this, Integer.parseInt(string))); return v; } public void onButtonPressed(Uri uri) { } @Override public void onAttach(Activity activity) { super.onAttach(activity); try { mListener = (OnFragmentInteractionListener) activity; } catch (ClassCastException e) { throw new ClassCastException(activity.toString() + " must implement OnFragmentInteractionListener"); } } @Override public void onDetach() { super.onDetach(); mListener = null; } public interface OnFragmentInteractionListener { public void onContentFragmentInteraction(String string); } } 

error

 03-02 18:46:47.254 1958-1958/com.peterchappy.lab5 E/AndroidRuntime﹕ FATAL EXCEPTION: main Process: com.peterchappy.lab5, PID: 1958 java.lang.RuntimeException: Unable to start activity ComponentInfo{com.peterchappy.lab5/com.peterchappy.lab5.MainActivity}: java.lang.ClassCastException: com.peterchappy.lab5.MainActivity@2298f3ca must implement OnFragmentInteractionListener at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2298) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360) at android.app.ActivityThread.access$800(ActivityThread.java:144) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:135) at android.app.ActivityThread.main(ActivityThread.java:5221) at java.lang.reflect.Method.invoke(Native Method) at java.lang.reflect.Method.invoke(Method.java:372) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694) Caused by: java.lang.ClassCastException: com.peterchappy.lab5.MainActivity@2298f3ca must implement OnFragmentInteractionListener at com.peterchappy.lab5.ContentFragmet.onAttach(ContentFragmet.java:83) at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:853) at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1067) at android.app.BackStackRecord.run(BackStackRecord.java:833) at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1452) at android.app.Activity.performStart(Activity.java:5948) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2261)            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)            at android.app.ActivityThread.access$800(ActivityThread.java:144)            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)            at android.os.Handler.dispatchMessage(Handler.java:102)            at android.os.Looper.loop(Looper.java:135)            at android.app.ActivityThread.main(ActivityThread.java:5221)            at java.lang.reflect.Method.invoke(Native Method)            at java.lang.reflect.Method.invoke(Method.java:372)            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694) 

  public interface OnFragmentInteractionListener { public void onNavFragmentInteraction(String string); } 

  public interface OnFragmentInteractionListener { public void onContentFragmentInteraction(String string); } 

  @Override public void onNavFragmentInteraction(String string) { // Do stuff } @Override public void onContentFragmentInteraction(String string) { // Do different stuff }