Java 错误：必须实现 OnFragmentInteractionListener
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时间：2020-08-11 06:53:28 来源:igfitidea点击:
ERROR: must implement OnFragmentInteractionListener
提问by Peter Chappy
It's trowing an error saying I must implment the OnFragmentInteractionListener, but as far as I'm aware I'm implementing it properly ... Any help would be greatly appreciated.
这是一个错误，说我必须实施 OnFragmentInteractionListener，但据我所知，我正在正确实施它......任何帮助将不胜感激。
Main Activity
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
导航片段
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
内容片段
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
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.access0(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.access0(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)
采纳答案by unrulygnu
The OnFragmentInteractionListenerinterfaces in both of your Fragments contain a method with the same signature, and MainActivityis implementing one method to try to cover both interfaces.
OnFragmentInteractionListener您Fragment的两个s 中的接口都包含一个具有相同签名的方法，并且MainActivity正在实现一种方法以尝试覆盖这两个接口。
Change the signature of one or both of the methods, then implement both methods in MainActivity. For example:
更改一个或两个方法的签名，然后在MainActivity. 例如：
NavFragment
导航片段
public interface OnFragmentInteractionListener {
public void onNavFragmentInteraction(String string);
}
ContentFragment
内容片段
public interface OnFragmentInteractionListener {
public void onContentFragmentInteraction(String string);
}
MainActivity
主要活动
@Override
public void onNavFragmentInteraction(String string) {
// Do stuff
}
@Override
public void onContentFragmentInteraction(String string) {
// Do different stuff
}
