Android片段后退按

Question

我有几个片段。但是当按下按钮时，所有的片段都会导致PeriodFragment。我的问题是如何实现，以便当用户按下手机上的BACK按钮时，PeriodFragment将切换回它从中输入的片段。 这是从PeriodFragment.java Java代码：

public class PeriodFragment extends Fragment { 

    Button btnPretrazi; 

    public PeriodFragment() { 
     // Required empty public constructor 
    } 


    @Override 
    public View onCreateView(LayoutInflater inflater, ViewGroup container, 
          Bundle savedInstanceState) { 
     // Inflate the layout for this fragment 

     View view = inflater.inflate(R.layout.fragment_period, container, false); 


     //buttonPretraziPeriod 
     btnPretrazi = (Button) view.findViewById(R.id.buttonPretraziPeriod); 

     btnPretrazi.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View v) { 
       Toast.makeText(getContext(),"test", Toast.LENGTH_SHORT).show(); 
      } 
     }); 


     return view; 
    } 

} 

这是我的TvrdjavaFragment.java（具有该按钮以切换到PeriodFragment.java的片段中的一个）：

package com.example.ivanp.msnis; 

public class TvrdjavaFragment extends Fragment { 

    Button btnIdinaperiod; 

    public TvrdjavaFragment() { 
     // Required empty public constructor 
    } 


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

     View view = inflater.inflate(R.layout.fragment_tvrdjava, container, false); 
     // Inflate the layout for this fragment 
     //show date 
     TextView datumprikaz = (TextView) view.findViewById(R.id.datumprikaz); 
     Date danas = new Date(); 

     SimpleDateFormat sdf = new SimpleDateFormat("dd.MM.yyyy"); 
     String novDatum = sdf.format(danas); 

     datumprikaz.setText(novDatum); 
     //End of show date 

     btnIdinaperiod = (Button) view.findViewById(R.id.buttonIdinaperiod); 

     btnIdinaperiod.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View v) { 
       PeriodFragment periodFragment = new PeriodFragment(); 
       FragmentTransaction periodFragmentTransaction = getActivity().getSupportFragmentManager().beginTransaction(); 
       periodFragmentTransaction.replace(R.id.frame, periodFragment); 
       periodFragmentTransaction.commit(); 
      } 
     }); 

     return view; 
    } 

} 

I”新的Android工作室，所以请告诉细节。

Answer 1

添加到堆栈中会解决这个问题：

periodFragmentTransaction.replace(R.id.frame, periodFragment); 
periodFragmentTransaction.addToBackStack(null); 
periodFragmentTransaction.commit(); 

Answer 2

According to android docs当你的应用程序中使用的片段，个别FragmentTransaction对象可表示应添加到后退堆栈环境的变化。例如，如果您通过交换碎片来实现手机上的主/明细流，则应确保在详细信息屏幕上按下“后退”按钮可将用户返回到主屏幕。为此，请在提交事务之前调用addToBackStack（）：

// Works with either the framework FragmentManager or the 
// support package FragmentManager (getSupportFragmentManager). 
getSupportFragmentManager().beginTransaction() 
         .add(detailFragment, "detail") 
         // Add this transaction to the back stack 
         .addToBackStack() 
         .commit();