我一直在寻找 stackoverflow 来解决我的问题并找到了一些很好的东西，但它对我不起作用或者我很愚蠢地看到它 ( How to implement OnFragmentInteractionListener )

我想在框架内放置一个 fragment ，所以我创建了它等等。我必须实现一个接口(interface)及其方法。我(认为)我做到了，但我的应用程序每次都崩溃...

*编辑:我的应用程序崩溃，当我调用 openHome 或 openRecommended 时，onCreate 方法有效，我收到这些错误，但一切都正确显示。

这是我的代码:

主 Activity .java

import android.app.Activity;
import android.app.FragmentManager;
import android.app.FragmentTransaction;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.view.View;


public class MainActivity extends Activity implements HomeFragment.OnFragmentInteractionListener, RecommendedFragment.OnFragmentInteractionListener
{
    FragmentTransaction fragmentTransaction;
    HomeFragment homeFragment;

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

        homeFragment = new HomeFragment();

        getFragmentManager().beginTransaction().add(R.id.mainFrame, homeFragment).commit();
    }

    protected void openHome(View view)
    {
        /*Intent homeIntent = new Intent(this, HomeFragment.class);
        startActivity(homeIntent);

        homeFragment = new HomeFragment();
        getFragmentManager().beginTransaction().replace(R.id.mainFrame, homeFragment).commit();*/

        System.out.println("Success");
    }

    public void openRecommended(View view)
    {
        Intent recommendedIntent = new Intent(this, RecommendedFragment.class);
        startActivity(recommendedIntent);

        RecommendedFragment recommendedFragment = new RecommendedFragment();
        getFragmentManager().beginTransaction().replace(R.id.mainFrame, recommendedFragment).commit();
    }

    @Override
    public void onFragmentInteractionHome(Uri uri)
    {

    }

    @Override
    public void onFragmentInteractionRecommended(Uri uri)
    {

    }
}

首页 fragment .java

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;


/**
 * A simple {@link Fragment} subclass.
 * Activities that contain this fragment must implement the
 * {@link HomeFragment.OnFragmentInteractionListener} interface
 * to handle interaction events.
 * Use the {@link HomeFragment#newInstance} factory method to
 * create an instance of this fragment.
 */
public class HomeFragment extends Fragment
{
    private OnFragmentInteractionListener mListener;


    public static HomeFragment newInstance()
    {
        HomeFragment fragment = new HomeFragment();
        return fragment;
    }

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

    @Override
    public void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
    }

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

    // TODO: Rename method, update argument and hook method into UI event
    public void onButtonPressed(Uri uri)
    {
        if (mListener != null)
        {
            mListener.onFragmentInteractionHome(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;
    }

    /**
     * This interface must be implemented by activities that contain this
     * fragment to allow an interaction in this fragment to be communicated
     * to the activity and potentially other fragments contained in that
     * activity.
     * <p/>
     * See the Android Training lesson <a href=
     * "http://developer.android.com/training/basics/fragments/communicating.html"
     * >Communicating with Other Fragments</a> for more information.
     */
    public interface OnFragmentInteractionListener
    {
        // TODO: Update argument type and name
        public void onFragmentInteractionHome(Uri uri);
    }
}

RecommendedFragment 看起来一样，除了一些方法有不同的名称。

我总是得到这个错误:

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.domain.app/com.domain.app.MainActivity}: java.lang.ClassCastException: com.domain.app.MainActivity@b1d296b0 must implement OnFragmentInteractionListener at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245) at android.app.ActivityThread.access$800(ActivityThread.java:135) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:136) at android.app.ActivityThread.main(ActivityThread.java:5017) at java.lang.reflect.Method.invokeNative(Native Method) at java.lang.reflect.Method.invoke(Method.java:515) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595) at dalvik.system.NativeStart.main(Native Method) Caused by: java.lang.ClassCastException: com.domain.app.MainActivity@b1d296b0 must implement OnFragmentInteractionListener at com.domain.app.HomeFragment.onAttach(HomeFragment.java:74) at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:849) at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1062) at android.app.BackStackRecord.run(BackStackRecord.java:684) at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1447) at android.app.Activity.performStart(Activity.java:5240) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2168)             at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)             at android.app.ActivityThread.access$800(ActivityThread.java:135)             at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)             at android.os.Handler.dispatchMessage(Handler.java:102)             at android.os.Looper.loop(Looper.java:136)             at android.app.ActivityThread.main(ActivityThread.java:5017)             at java.lang.reflect.Method.invokeNative(Native Method)             at java.lang.reflect.Method.invoke(Method.java:515)             at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)             at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)             at dalvik.system.NativeStart.main(Native Method)

我真的需要帮助，我被困了几个小时......

约翰

最佳答案

我删除了无用的引用以及与 RecommendedFragment 类相关的所有内容。如果您发布它，我会更新我的答案。

我已经测试过它并且有效。但是请尝试解释 openHome() 方法的含义，因为根据您的代码从未使用过它，但是您说调用它时应用程序崩溃了。

我将此方法添加到界面中，因为在我看来这是最合乎逻辑的事情。

//主 Activity

public class MainActivity extends Activity implements HomeFragment.OnFragmentInteractionListener {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        getFragmentManager().beginTransaction()
                .add(R.id.mainFrame, new HomeFragment())
                .commit();
    }

    @Override
    public void openHome(View view) {
        System.out.println("Success");
    }

    @Override
    public void onFragmentInteractionHome(Uri uri) {
        Toast.makeText(this, "Success", Toast.LENGTH_SHORT).show();
    }

}

//首页 fragment

public class HomeFragment extends Fragment {

    private OnFragmentInteractionListener mListener;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        return inflater.inflate(R.layout.fragment_home, container, false);
    }

    public void onButtonPressed(Uri uri) {
        if (mListener != null) {
            mListener.onFragmentInteractionHome(uri);
        }
    }

    @Override
    public void onAttach(Activity activity) {
        super.onAttach(activity);
        try {
            mListener = (OnFragmentInteractionListener) activity;
            mListener.onFragmentInteractionHome(Uri.parse("doWhatYouWant"));
        } catch (ClassCastException e) {
            throw new ClassCastException(activity.toString()
                    + " must implement OnFragmentInteractionListener");
        }
    }

    @Override
    public void onDetach() {
        super.onDetach();
        mListener = null;
    }


    public interface OnFragmentInteractionListener {
        public void onFragmentInteractionHome(Uri uri);
        public void openHome(View view);
    }

}

关于java - Android: fragment 交互监听器出错，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/25753953/