Question

在发布之前我已经尝试过几个方面，其中一个是关注此stackoverflow： How to change fragments using Android navigation drawer

然而，当我尝试在那里发布的一些解决方案时，即使片段是由android studio创建的，我也会收到错误。它说的是关于fragment.v4的东西，而在整个由android studio创建的片段中使用了它。

这是我的代码：

@Override
public void onNavigationDrawerItemSelected(int position) {
    // update the main content by replacing fragments
    FragmentManager fragmentManager = getSupportFragmentManager();
    Fragment fragment = new Fragment();
    switch(position) {
        case 1:
            fragment = new WeatherFragment();
            break;
        case 2:
            fragment = new WeatherFragment();
            break;
    }
    fragmentManager.beginTransaction().replace(R.id.container, fragment).commit();
}

点击第二项时我尝试更改的天气片段未显示。

任何提示？

这是我当前的错误：

06-10 05：28：23.247 24328-24328 / nl.shacklez.mijnrecepten E / AndroidRuntime：FATAL EXCEPTION：main 处理：nl.shacklez.mijnrecepten，PID：24328 java.lang.ClassCastException：nl.shacklez.mijnrecepten.MainActivity@2c5b3c99必须实现OnFragmentInteractionListener 在nl.shacklez.mijnrecepten.WeatherFragment.onAttach（WeatherFragment.java:83）在android.app.FragmentManagerImpl.moveToState（FragmentManager.java:853）在android.app.FragmentManagerImpl.moveToState（FragmentManager.java:1067）在android.app.BackStackRecord.run（BackStackRecord.java:833）在android.app.FragmentManagerImpl.execPendingActions（FragmentManager.java:1452）在android.app.FragmentManagerImpl $ 1.run（FragmentManager.java:447）在android.os.Handler.handleCallback（Handler.java:739）在android.os.Handler.dispatchMessage（Handler.java:95）在android.os.Looper.loop（Looper.java:135）在android.app.ActivityThread.main（ActivityThread.java:5221） at java.lang.reflect.Method.invoke（Native Method）在java.lang.reflect.Method.invoke（Method.java:372）在com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:899）在com.android.internal.os.ZygoteInit.main（ZygoteInit.java:694）

这是我的weatherFrag课程：

package nl.shacklez.mijnrecepten;

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;


public class WeatherFragment extends Fragment {
// TODO: Rename parameter arguments, choose names that match
// the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
private static final String ARG_PARAM1 = "param1";
private static final String ARG_PARAM2 = "param2";

// TODO: Rename and change types of parameters
private String mParam1;
private String mParam2;

private OnFragmentInteractionListener mListener;

/**
 * Use this factory method to create a new instance of
 * this fragment using the provided parameters.
 *
 * @param param1 Parameter 1.
 * @param param2 Parameter 2.
 * @return A new instance of fragment WeatherFragment.
 */
// TODO: Rename and change types and number of parameters
public static WeatherFragment newInstance(String param1, String param2) {
    WeatherFragment fragment = new WeatherFragment();
    Bundle args = new Bundle();
    args.putString(ARG_PARAM1, param1);
    args.putString(ARG_PARAM2, param2);
    fragment.setArguments(args);
    return fragment;
}

public WeatherFragment() {
    // 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) {
    // Inflate the layout for this fragment
    return inflater.inflate(R.layout.fragment_weather, container, false);
}

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

}

Answer 1

首先确保您的片段确实扩展了Fragment，然后使用此代码：

@SuppressLint("NewApi")
 void displayView(int position) {
        // update the main content by replacing fragments
        Fragment fragment = null;
        switch (position) {
        case 0:
            fragment = new firstFragment();
            break;
        case 2:
        fragment = new secondFragment();
        break;
    default:
            break;
        }
    if (fragment != null) {
            FragmentManager fragmentManager = getFragmentManager();
            fragmentManager.beginTransaction()
                    .replace(R.id.frame_container, fragment).commit();

            // update selected item and title, then close the drawer

            mDrawerList.setItemChecked(position, true);
            mDrawerList.setSelection(position);
            setTitle(navMenuTitles[position]);
            mDrawerLayout.closeDrawer(mDrawerList);
        } else {
            // error in creating fragment
            Log.e("MainActivity", "Error in creating fragment");
        }
    }

如果你不喜欢使用支持片段而不是android.app.Fragment;

尝试导入V4 fragment如果仍然显示错误，请确保已从SDK管理器安装Android Support Library，您还可以检查依赖项并重新同步项目。

希望这会有所帮助

Answer 2

查看以下代码，

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

在你的片段中。你必须实现这个

public interface OnFragmentInteractionListener {
    // TODO: Update argument type and name
    public void onFragmentInteraction(Uri uri);
}

您活动中片段的界面。这意味着您的活动应该实现WeatherFragment.OnFragmentInteractionListener。这个思想是Android Studio创建的片段的一个特性。它创建此接口以在片段和活动之间进行通信。通常我会在onAttach函数中的super.onAttach（activity）之后删除代码。

Android导航抽屉更改片段无效

2 个答案: