为什么在按下后退按钮时会调用当前片段的 oncreateview？

Question

我正在尝试从后台检索片段。它正在被检索，但问题是在按下后退按钮时，oncreate 视图和当前片段的后续生命周期方法也被调用。这是我将片段放入后台堆栈的代码：

fragment=new FileTrackingFragment();
bundle=new Bundle();
bundle.putString("name","Dak Monitoring");
bundle.putInt("num",2);
fragment.setArguments(bundle);
ft.replace(R.id.parent, fragment, fragment.getClass().getName());
ft.addToBackStack(fragment.getClass().getName());
ft.commit();
break;

片段代码如下：

package com.example.rajvirsingh.epunjaboffice.DakMonitoring;

import android.app.Activity;
import android.app.ProgressDialog;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.design.widget.Snackbar;
import android.support.percent.PercentRelativeLayout;
import android.support.v4.app.Fragment;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Spinner;
import android.widget.TextView;
import android.widget.Toast;

import com.example.rajvirsingh.epunjaboffice.FileTracking.HistoryAdapter;
import com.example.rajvirsingh.epunjaboffice.MainActivity;
import com.example.rajvirsingh.epunjaboffice.R;
import com.example.rajvirsingh.epunjaboffice.Utility.Constants;
import com.example.rajvirsingh.epunjaboffice.Utility.SessionManager;
import com.loopj.android.http.AsyncHttpClient;
import com.loopj.android.http.RequestParams;
import com.loopj.android.http.TextHttpResponseHandler;

import org.json.JSONArray;

import java.util.ArrayList;

import cz.msebera.android.httpclient.Header;

/**
 * Created by rajvirsingh on 07/03/17.
 */

public class ConsolidatedReportFragment extends Fragment implements AdapterView.OnItemSelectedListener {
  SessionManager sessionManager;
  JSONArray consolidatedRJsonArray;
  String userCode,branchCode;
  MainActivity mainActivity;
  Spinner spinDuration;
  String selectedDuration="";
  ProgressDialog pDialog;
  TextView error,serial;
  PercentRelativeLayout pl;
  PercentRelativeLayout ll;
  RecyclerView recyclerView;
  AsyncHttpClient client = new AsyncHttpClient();
  String []durationValues={"This Week","This Month","This Year","Total"};


  @Nullable
  @Override
  public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
    return inflater.inflate(R.layout.fragment_dak_monitoring_consolidated,container,false);
  }


  @Override
  public void onAttach(Activity activity) {
    super.onAttach(activity);
    sessionManager=SessionManager.NewInstance(activity);
    userCode=sessionManager.pref.getString("usercode","");
    branchCode=sessionManager.pref.getString("branchcode","");
    mainActivity=(MainActivity) getActivity();
    if(((AppCompatActivity) getActivity()).getSupportActionBar()!=null) {
      ((AppCompatActivity) getActivity()).getSupportActionBar().show();
      mainActivity.setToolbarTitle("Consolidated Report");
      mainActivity.unlockDrawer();
      mainActivity.loadNavigationMenu(R.menu.menu_dak_monitoring);
    }
  }

  @Override
  public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
    super.onViewCreated(view, savedInstanceState);

    pDialog = new ProgressDialog(getActivity(),R.style.DialogStyle);
    pDialog.setMessage("Loading...");
    pDialog.setTitle("Office Management");
    pDialog.setIndeterminate(true);
    pDialog.setCancelable(true);

    sessionManager=SessionManager.NewInstance(getActivity());

    error=(TextView)view.findViewById(R.id.err);
    serial=(TextView)view.findViewById(R.id.serial);


    spinDuration=(Spinner)view.findViewById(R.id.spin_duration);
    ArrayAdapter<String> arrayAdapter=new ArrayAdapter<String>(getActivity(),android.R.layout.simple_spinner_item,durationValues);
    arrayAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
    spinDuration.setAdapter(arrayAdapter);
    spinDuration.setOnItemSelectedListener(this);
    spinDuration.setSelection(0);
    selectedDuration="1";

    pl=(PercentRelativeLayout)view.findViewById(R.id.percentile);

    ll=(PercentRelativeLayout) view.findViewById(R.id.ll1);
    recyclerView=(RecyclerView)view.findViewById(R.id.recyclerView);

    if(Constants.isOnline(getActivity()))
    {

      getConsolidatedReport();
    }
  }

  void getConsolidatedReport()
  {
    RequestParams params = new RequestParams();
    params.put("_userMasterCode",userCode);
    params.put("_parameter", selectedDuration);
    String url=getString(R.string.urlGetConsolidatedMonitoringReport);

    client.get(url, params, new TextHttpResponseHandler() {
      @Override
      public void onFailure(int statusCode, Header[] headers, String responseString, Throwable throwable) {
        pDialog.dismiss();
        ll.setVisibility(View.GONE);
        recyclerView.setVisibility(View.GONE);
        error.setVisibility(View.VISIBLE);
        if(getView()!=null)
          Snackbar.make(getView(), "Error!", Snackbar.LENGTH_LONG).show();
      }

      @Override
      public void onSuccess(int statusCode, Header[] headers, String responseString) {

        try {
          pDialog.dismiss();
          int p1 = responseString.indexOf(">");
          int p2 = responseString.lastIndexOf("<");
          String r = responseString.substring(p1 + 1, p2);
          p1 = r.indexOf(">");
          r = r.substring(p1 + 1, r.length());
          ll.setVisibility(View.VISIBLE);
          recyclerView.setVisibility(View.VISIBLE);
          error.setVisibility(View.GONE);
          consolidatedRJsonArray = new JSONArray(r);
          ConsolidatedReportAdapter consolidatedReportAdapter=new ConsolidatedReportAdapter(consolidatedRJsonArray,getActivity());
          recyclerView.setAdapter(consolidatedReportAdapter);
          recyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
        } catch (Exception e) {
          if (getActivity() != null && isAdded()) {
            ll.setVisibility(View.GONE);
            recyclerView.setVisibility(View.GONE);
            error.setVisibility(View.VISIBLE);
            if(getView()!=null)
              Snackbar.make(getView(), "No Information Exist! For Selection", Snackbar.LENGTH_LONG).show();
            else
              Toast.makeText(getActivity(),"No Information Exist! For Selection",Toast.LENGTH_LONG).show();
            pDialog.dismiss();
          }
        }
      }
    });
  }

  @Override
  public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
    switch (parent.getId())
    {
      case R.id.spin_duration:
        selectedDuration=String.valueOf(position+1);
        getConsolidatedReport();
        break;
    }
  }

  @Override
  public void onNothingSelected(AdapterView<?> parent) {

  }

  @Override
  public void onPause() {
    super.onPause();
    pDialog.dismiss();
  }

  @Override
  public void onStop() {
    client.cancelAllRequests(true);
    super.onStop();
  }

}

Answer 1

当您移动到下一个片段时，当您的视图被破坏时，它将调用它，因此它会在按下后退按钮时再次要求查看，这应该是在内存中保持片段视图（当前不可见）的方法稍后会导致内存问题。它是 onCreate() 方法，不会再次调用。

如果您不想在后按时调用 onCreateView，请使用 ft.add(R.id.parent, fragment, fragment.getClass().getName());

有关片段堆栈行为方式的更多详细信息，请参阅here。