我正在尝试在我的片段中使用onBackPressed((，以便我可以允许用户回滚他在应用程序中导航的一堆片段。
问题是，当我将下面的方法添加到我的片段时，它给了我错误：Method does not override method from its superclass.
@Override
public void onBackPressed() {
android.support.v4.app.FragmentManager fragmentManager = getFragmentManager();
fragmentManager.popBackStack();
}
你知道为什么吗？
谢谢！
整个片段如下：
package it.bitrack.fabio.bitrack;
import android.content.Context;
import android.net.Uri;
import android.os.Bundle;
//import android.app.Fragment;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ListView;
import android.widget.ArrayAdapter;
import java.util.ArrayList;
import java.util.Arrays;
import android.view.KeyEvent;
/**
* A simple {@link Fragment} subclass.
* Activities that contain this fragment must implement the
* {@link AssetMngtView.OnFragmentInteractionListener} interface
* to handle interaction events.
* Use the {@link AssetMngtView#newInstance} factory method to
* create an instance of this fragment.
*/
public class AssetMngtView 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";
View view;
ListView assetMngtListView;
ArrayAdapter<String> listAdapter;
// TODO: Rename and change types of parameters
private String mParam1;
private String mParam2;
private OnFragmentInteractionListener mListener;
public AssetMngtView() {
// Required empty public constructor
}
/**
* 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 AssetMngtView.
*/
// TODO: Rename and change types and number of parameters
public static AssetMngtView newInstance(String param1, String param2) {
AssetMngtView fragment = new AssetMngtView();
Bundle args = new Bundle();
args.putString(ARG_PARAM1, param1);
args.putString(ARG_PARAM2, param2);
fragment.setArguments(args);
return fragment;
}
@Override
public void onBackPressed() {
android.support.v4.app.FragmentManager fragmentManager = getFragmentManager();
fragmentManager.popBackStack();
}
@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
view = inflater.inflate(R.layout.fragment_asset_mngt_view, container, false);
assetMngtListView = (ListView) view.findViewById(R.id.assetMngtListView);
setListView();
return view;
}
public void setListView() {
String[] options = new String[]{"Bind tag & thing", "Create new thing", "Edit existent thing", "Maintain existent thing", "View things notifications"};
ArrayList<String> optionsList = new ArrayList<String>();
optionsList.addAll(Arrays.asList(options));
listAdapter = new ArrayAdapter<>(getContext(), android.R.layout.simple_list_item_1, optionsList);
assetMngtListView.setAdapter(listAdapter);
}
// 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(Context context) {
super.onAttach(context);
if (context instanceof OnFragmentInteractionListener) {
mListener = (OnFragmentInteractionListener) context;
} else {
throw new RuntimeException(context.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
void onFragmentInteraction(Uri uri);
}
}
如果要在片段中实现onBackPressing行为，则应在片段的onViewCreated中执行此操作：
requireActivity().getOnBackPressedDispatcher().addCallback(new OnBackPressedCallback(true) {
@Override
public void handleOnBackPressed() {
if (isHandlingBackPressInFragment()) {
// Handle back press
} else {
// If you want to get default implementation of onBackPressed, use this
this.remove();
requireActivity().onBackPressed();
}
}
});
要实现您想要的，您应该覆盖关联Activity的onBackPressed()，如下所示：
@Override
public void onBackPressed() {
if (getSupportFragmentManager().getBackStackEntryCount() > 1) {
getSupportFragmentManager().popBackStack();
} else {
finish();
}
}
希望这有帮助。 对不起我的英语。
问题是Fragment没有public void onBackPressed()方法。
您收到错误是因为您的方法用@Override进行了注释，但它实际上并没有覆盖超类中的任何方法。@Override的目的正是这个，让你知道你认为你正在覆盖某些东西，但实际上，你并没有
附带说明一下，您尝试做的事情是不必要的。 如果您按下后退按钮并且后退堆栈中有片段，它们将自动弹出。 试试这个
public class FragmentsActivity extends AppCompatActivity {
public static class FragmentA extends Fragment {
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
View view = new TextView(getActivity());
view.setLayoutParams(new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT));
view.setBackgroundColor(0xffff0000);
return view;
}
}
public static class FragmentB extends Fragment {
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
View view = new TextView(getActivity());
view.setLayoutParams(new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT));
view.setBackgroundColor(0xff00ff00);
return view;
}
}
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_fragments);
FragmentManager fm = getSupportFragmentManager();
fm.beginTransaction()
.add(R.id.fragment_container, new FragmentA(), FragmentA.class.getSimpleName())
.commit();
// notice addToBackStack here
fm.beginTransaction()
.add(R.id.fragment_container, new FragmentB(), FragmentB.class.getSimpleName())
.addToBackStack(FragmentB.class.getSimpleName())
.commit();
}
}
使用方法 onBackPressed(( 并在 Activity 类中调用 popBackStack((，而不是在片段中调用
如果你想回到上一个片段，你可以使用它。content_frame是框架布局的 ID。您不能使用 onBackPress，因为没有活动，片段就无法独立存在。
FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
ft.replace(R.id.content_frame, new MainActivity());
ft.addToBackStack(null);
ft.commit();
如果我误解或遗漏了某些内容，我很抱歉，但您会收到错误，因为 onBackPressed(( 不是超类的方法(在您的情况下是片段类(