Question

它提出了一个错误，说我必须实施OnFragmentInteractionListener，但据我所知，我正确地实施了它......任何帮助都将不胜感激。

主要活动

    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);
    }

}

ContentFragment

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);
    }
}

错误

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)

Answer 1

两个Fragment中的OnFragmentInteractionListener接口都包含一个具有相同签名的方法，而MainActivity正在实现一种方法来尝试覆盖这两个接口。

更改一个或两个方法的签名，然后在MainActivity中实现这两个方法。例如：

<强> NavFragment

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

<强> ContentFragment

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

<强> MainActivity

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

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

错误：必须实现OnFragmentInteractionListener

1 个答案: