从堆栈弹出片段

Question

我正在尝试创建一个包含两个片段的活动。 活动开始时显示一个片段，而用户按下工具栏中的一个按钮则显示另一个片段。

在第二个片段中，我想添加向后导航，当用户按下“后退”按钮时，第二个片段应关闭，第一个片段应出现。

但是我遇到一些错误，无法修复。

MainActivity.java

package com.geapps.notapp.activities;

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.support.v7.app.ActionBarActivity;
import android.support.v7.widget.Toolbar;
import android.view.MenuItem;
import android.view.View;

import com.geapps.notapp.R;
import com.geapps.notapp.fragments.MainFragment;
import com.geapps.notapp.fragments.NewNoteFragment;

public class MainActivity extends ActionBarActivity
{
    @Override
    protected void onCreate(Bundle savedInstanceState) 
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        if (savedInstanceState == null) 
        {
            loadFragment(new MainFragment(), "Main");
        }

        Toolbar toolbar = (Toolbar)findViewById(R.id.toolbar);
        toolbar.setTitle("Toolbar");
        toolbar.inflateMenu(R.menu.main);


        toolbar.setOnMenuItemClickListener(new Toolbar.OnMenuItemClickListener() 
        {
            @Override
            public boolean onMenuItemClick(MenuItem menuItem) 
            {
                switch (menuItem.getItemId())
                {
                    case R.id.action_new:
                        loadFragment(new NewNoteFragment(), "New Note");
                        break;
                }

                return false;
            }
        });
    }

    public void loadFragment(Fragment fragment, String tag)
    {
        FragmentManager fragmentManager = getSupportFragmentManager();
        FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();

        fragmentTransaction.replace(R.id.main_container, fragment, tag);
        fragmentTransaction.addToBackStack(tag);
        fragmentTransaction.commit();
    }
} 

MainFragment.java

package com.geapps.notapp.fragments;

import java.util.ArrayList;

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ListView;

import com.geapps.notapp.R;
import com.geapps.notapp.adapters.NotesListAdapter;
import com.geapps.notapp.models.Note;

public class MainFragment extends Fragment 
{
    private View view;

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

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
    {
        view = inflater.inflate(R.layout.fragment_main, container, false);

        loadNotes();

        return view;
    }

    private void loadNotes()
    {
        ListView notesList = (ListView)view.findViewById(R.id.notes_list);

        ArrayList<Note> notes = new ArrayList<Note>();
        notes.add(new Note("Sunday homework", "1. Do math homework and then sleep"));
        notes.add(new Note("Job details", "Programming job especially iOS and Android development"));
        notes.add(new Note("Journal Part 1", "What am I going to do now? I have no way to run .. :("));

        NotesListAdapter notesListAdapter = new NotesListAdapter(this.getActivity(), notes);
        notesList.setAdapter(notesListAdapter);
    }
}

NewNoteFragment.java

package com.geapps.notapp.fragments;

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v7.widget.Toolbar;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

import com.geapps.notapp.R;

public class NewNoteFragment extends Fragment 
{
    private View view;

    public void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setRetainInstance(true);
    }

    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
    {
        view = inflater.inflate(R.layout.fragment_new_note, container, false);

        Toolbar toolbar = (Toolbar)getActivity().findViewById(R.id.toolbar);
        toolbar.getMenu().findItem(R.id.action_new).setVisible(false);

        toolbar.setNavigationIcon(R.drawable.ic_action_back);
        toolbar.setNavigationOnClickListener(new View.OnClickListener() 
        {
            @Override
            public void onClick(View v) 
            {
                FragmentManager fragmentManager = getActivity().getSupportFragmentManager();
                fragmentManager.popBackStack("Main", FragmentManager.POP_BACK_STACK_INCLUSIVE);
            }
        });

        return view;
    }
}

这是错误：

PathClassLoader(BaseDexClassLoader).findClass(String) line: 61  
PathClassLoader(ClassLoader).loadClass(String, boolean) line: 501   
PathClassLoader(ClassLoader).loadClass(String) line: 461    
BackStackRecord.getEnterTransition(Fragment, boolean) line: 1056    
BackStackRecord.configureTransitions(int, BackStackRecord$TransitionState, boolean, SparseArray, SparseArray) line: 1138    
BackStackRecord.beginTransition(SparseArray, SparseArray, boolean) line: 1029   
BackStackRecord.popFromBackStack(boolean, BackStackRecord$TransitionState, SparseArray, SparseArray) line: 883  
FragmentManagerImpl.popBackStackState(Handler, String, int, int) line: 1593 
FragmentManagerImpl$3.run() line: 509   
FragmentManagerImpl.execPendingActions() line: 1489 
FragmentManagerImpl$1.run() line: 454   
Handler.handleCallback(Message) line: 615   
FragmentActivity$1(Handler).dispatchMessage(Message) line: 92   
Looper.loop() line: 137 
ActivityThread.main(String[]) line: 4921    
Method.invokeNative(Object, Object[], Class, Class[], Class, int, boolean) line: not available [native method]  
Method.invoke(Object, Object...) line: 511  
ZygoteInit$MethodAndArgsCaller.run() line: 1038 
ZygoteInit.main(String[]) line: 805 
NativeStart.main(String[]) line: not available [native method]  

Answer 1

试试这个

getActivity().getSupportFragmentManager().popBackStack();

Answer 2

让系统自行处理，而不是自定义。 进行以下更改并尝试一下：

 public void loadFragment(Fragment fragment, String tag)
{
    FragmentManager fragmentManager = getSupportFragmentManager();
    FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();

    fragmentTransaction.replace(R.id.main_container, fragment, tag);


//    fragmentTransaction.addToBackStack(tag);
    fragmentTransaction.addToBackStack(null);

    fragmentTransaction.commit();
}

和

 toolbar.setNavigationOnClickListener(new View.OnClickListener() 
    {
        @Override
        public void onClick(View v) 
        {
            FragmentManager fragmentManager = getActivity().getSupportFragmentManager();
   //         fragmentManager.popBackStack("Main", FragmentManager.POP_BACK_STACK_INCLUSIVE);
   //         fragmentManager.popBackStack(); 
              getActivity().onBackPressed(); 
        }
    });

Answer 3

虽然很晚，但为方便起见，请尝试以下操作：

当您将第一个片段添加到活动中之前，请在提交前调用addToBackStack（null），这将允许第二个片段中的用户按后退按钮返回第一个片段。

getFragmentManager().beginTransaction().replace(R.id.main_container, fragment).addToBackStack(null).commit();

现在，将其添加到第二个片段的on单击方法中，以删除第二个片段并返回第一个片段。

 getActivity().getFragmentManager().beginTransaction().remove(this).commit();
            //now recreating main activity to return to first fragment
                getActivity().recreate();

替代方法和更好的方法是使用界面， 请参见此处的android文档

Answer 4

尝试以下三种方法中的任何一种

1.＃

getActivity().getSupportFragmentManager().popBackStack();

2.＃

    getActivity().getSupportFragmentManager().popBackStack(null, FragmentManager.POP_BACK_STACK_INCLUSIVE);

3.＃

getActivity().getSupportFragmentManager().popBackStackImmediate(null, FragmentManager.POP_BACK_STACK_INCLUSIVE);