对于那些谁使用静态片段

在这种情况下，如果你有一个静态片段，那么它会更可取。 为片段创建一个实例对象

private static MyFragment instance=null;

在MyFragment的onCreate()中初始化该实例

  instance=this;

也可以创建一个函数来获取Instance

 public static MyFragment getInstance(){
   return instance;
}

也可以创建函数

public boolean allowBackPressed(){
    if(allowBack==true){
        return true;
    }
    return false;
}


 //allowBack is a boolean variable that will be set to true at the action 
 //where you want that your backButton should not close activity. In my case I open 
 //Navigation Drawer then I set it to true. so when I press backbutton my 
 //drawer should be get closed

public void performSomeAction(){
    //.. Your code
    ///Here I have closed my drawer
}

在你能做的活动中

@Override
public void onBackPressed() {

    if (MyFragment.getInstance().allowBackPressed()) { 
        MyFragment.getInstance().performSomeAction();
    }
    else{
        super.onBackPressed();
    }
}

工作代码:

package com.example.keralapolice;

import android.app.Fragment;
import android.app.FragmentManager;
import android.app.FragmentManager.OnBackStackChangedListener;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.Gravity;
import android.view.KeyEvent;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Toast;

public class ChiefFragment extends Fragment {
    View view;

    // public OnBackPressedListener onBackPressedListener;

    @Override
    public View onCreateView(LayoutInflater inflater,
            ViewGroup container, Bundle args) {

        view = inflater.inflate(R.layout.activity_chief, container, false);
        getActivity().getActionBar().hide();
        view.setFocusableInTouchMode(true);
        view.requestFocus();
        view.setOnKeyListener(new View.OnKeyListener() {
            @Override
            public boolean onKey(View v, int keyCode, KeyEvent event) {
                Log.i(getTag(), "keyCode: " + keyCode);
                if (keyCode == KeyEvent.KEYCODE_BACK) {
                    getActivity().getActionBar().show();
                    Log.i(getTag(), "onKey Back listener is working!!!");
                    getFragmentManager().popBackStack(null, FragmentManager.POP_BACK_STACK_INCLUSIVE);
                    // String cameback="CameBack";
                    Intent i = new Intent(getActivity(), home.class);
                    // i.putExtra("Comingback", cameback);
                    startActivity(i);
                    return true;
                } else {
                    return false;
                }
            }
        });
        return view;
    }
}

使用addToBackStack方法替换一个片段:

getFragmentManager().beginTransaction().replace(R.id.content_frame, fragment).addToBackStack("my_fragment").commit();

然后在您的活动中，使用以下代码从一个片段返回到另一个片段(前一个片段)。

@Override
public void onBackPressed() {
    if (getParentFragmentManager().getBackStackEntryCount() > 0) {
        getParentFragmentManager().popBackStack();
    } else {
        super.onBackPressed();
    }
}

在你的oncreateView()方法中，你需要写这些代码，在KEYCODE_BACk条件下，你可以写任何你想要的功能

View v = inflater.inflate(R.layout.xyz, container, false);
//Back pressed Logic for fragment 
v.setFocusableInTouchMode(true); 
v.requestFocus(); 
v.setOnKeyListener(new View.OnKeyListener() { 
    @Override 
    public boolean onKey(View v, int keyCode, KeyEvent event) {
        if (event.getAction() == KeyEvent.ACTION_DOWN) {
            if (keyCode == KeyEvent.KEYCODE_BACK) {
                getActivity().finish(); 
                Intent intent = new Intent(getActivity(), MainActivity.class);
                startActivity(intent);

                return true; 
            } 
        } 
        return false; 
    } 
}); 

创建接口:

后退按钮处理程序接口

public interface BackButtonHandlerInterface {
    void addBackClickListener (OnBackClickListener onBackClickListener);
    void removeBackClickListener (OnBackClickListener onBackClickListener);
}

OnBackClickListener

public interface OnBackClickListener {
     boolean onBackClick();
}

在活动:

public class MainActivity extends AppCompatActivity implements BackButtonHandlerInterface {

    private ArrayList<WeakReference<OnBackClickListener>> backClickListenersList = new ArrayList<>();

    @Override
    public void addBackClickListener(OnBackClickListener onBackClickListener) {
        backClickListenersList.add(new WeakReference<>(onBackClickListener));
    }

    @Override
    public void removeBackClickListener(OnBackClickListener onBackClickListener) {
        for (Iterator<WeakReference<OnBackClickListener>> iterator = backClickListenersList.iterator();
         iterator.hasNext();){
            WeakReference<OnBackClickListener> weakRef = iterator.next();
            if (weakRef.get() == onBackClickListener){
                iterator.remove();
            }
        }
    }

    @Override
    public void onBackPressed() {
        if(!fragmentsBackKeyIntercept()){
            super.onBackPressed();
        }
    }

    private boolean fragmentsBackKeyIntercept() {
        boolean isIntercept = false;
        for (WeakReference<OnBackClickListener> weakRef : backClickListenersList) {
            OnBackClickListener onBackClickListener = weakRef.get();
            if (onBackClickListener != null) {
                boolean isFragmIntercept = onBackClickListener.onBackClick();
                if (!isIntercept) isIntercept = isFragmIntercept;
            }
        }
        return isIntercept;
    }
}

在片段:

public class MyFragment extends Fragment implements OnBackClickListener{

    private BackButtonHandlerInterface backButtonHandler;

    @Override
    public void onAttach(Activity activity) {
        super.onAttach(activity);
        backButtonHandler = (BackButtonHandlerInterface) activity;
        backButtonHandler.addBackClickListener(this);
    }

    @Override
    public void onDetach() {
        super.onDetach();
        backButtonHandler.removeBackClickListener(this);
        backButtonHandler = null;
    }

    @Override
    public boolean onBackClick() {
        //This method handle onBackPressed()! return true or false
        return false;
    }

}

更新

提供自定义向后导航

class MyFragment : Fragment() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        // This callback will only be called when MyFragment is at least Started.
        val callback = requireActivity().onBackPressedDispatcher.addCallback(this) {
            // Handle the back button event
        }

        // The callback can be enabled or disabled here or in the lambda
    }

}

在您的活动中添加此代码

@Override

public void onBackPressed() {
    if (getFragmentManager().getBackStackEntryCount() == 0) {
        super.onBackPressed();
    } else {
        getFragmentManager().popBackStack();
    }
}

并在commit()之前在Fragment中添加这一行

ft.addToBackStack(任何名称);