使用 Bundle 将字符串值从活动发送到片段返回 null答案

【问题标题】：Send string values from activity to fragment using Bundle returns null使用 Bundle 将字符串值从活动发送到片段返回 null
【发布时间】：2018-05-25 02:24:09
【问题描述】：

我有一个底部导航栏，其中包含用户可以选择的 4 个菜单项。根据他们选择的内容确定在我的框架中显示哪个片段。我可以加载片段并与它们交互。但我还需要向每个片段发送一些字符串值，但无法弄清楚我哪里出错了。当我开始我的片段并尝试使用 getArguments() 访问我的值时，它总是返回 null。以下是我的代码：

unitactivity.java 我在其中运行用于选择片段的代码

import android.app.ProgressDialog;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.design.widget.BottomNavigationView;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.MenuItem;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import java.util.HashMap;

public class UnitActivity extends AppCompatActivity {

    private BottomNavigationView bottomNavigation;
    private Fragment fragment;
    private FragmentManager fragmentManager;

    Boolean CheckEditText;
    ProgressDialog progressDialog;

    String ReadOnly;
    String LexaUser;
    String Password;
    String QA;
    String SearchValue;
    String UnitId;
    String UnitSize;
    String UnitStatus;

    Button UnitDetailsHeader;
    TextView UnitSizeText;
    TextView UnitStatusText;

    String finalResultUnitDetails;
    String HttpURLUnitDetails = "https://[path/to/server]/getUnitDetails.php";
    HashMap<String, String> hashMapUnitDetails = new HashMap<>();
    HttpParse httpParse = new HttpParse();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_units);

        Intent intent = getIntent();

        LexaUser = intent.getStringExtra("UserName");
        ReadOnly = intent.getStringExtra("ReadOnly");
        Password = intent.getStringExtra("Password");
        QA = intent.getStringExtra("QA");
        SearchValue = intent.getStringExtra("SearchInput");

        bottomNavigation = (BottomNavigationView)findViewById(R.id.bottom_navigation);
        bottomNavigation.inflateMenu(R.menu.bottom_menu);
        fragmentManager = getSupportFragmentManager();

        bottomNavigation.getMenu().getItem(0).setChecked(true);

        UnitDetailsHeader = findViewById(R.id.UnitDetailsViewTitle);
        UnitDetailsHeader.setText(SearchValue);

        UnitSizeText = findViewById(R.id.UnitSize);
        UnitStatusText = findViewById(R.id.UnitStatus);

        if (SearchValue.contains("-")) {
            getUnitDetails(SearchValue, LexaUser);
        } else {
            getSiblings();
        }

        bottomNavigation.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
            @Override
            public boolean onNavigationItemSelected(@NonNull MenuItem item) {
                int id = item.getItemId();

                switch (id){
                    case R.id.action_search:
                        fragment = new NewUnitStatusFragment();
                        break;
                    case R.id.action_cart:
                        fragment = new PendingUnitStatusFragment();
                        break;
                    case R.id.action_hot_deals:
                        fragment = new FinalUnitStatusFragment();
                        break;
                    case R.id.action_siblings:
                        fragment = new SiblingUnitFragment();
                        break;
                }

                Bundle connBundle = new Bundle();
                connBundle.putString("SearchValue", SearchValue);
                connBundle.putString("LexaUser", LexaUser);
                connBundle.putString("Password", Password);
                connBundle.putString("QA", QA);

                fragment.setArguments(connBundle);

                final FragmentTransaction transaction = fragmentManager.beginTransaction();
                transaction.replace(R.id.main_container, fragment).commit();

                return true;
            }
        });
    }
}

当我尝试访问片段中的值时：(onCreateView)

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

    Bundle bundle = getArguments();

    if (bundle != null) {
        SearchValue = bundle.getString("SearchValue");
        LexaUser = bundle.getString("LexaUser");
        Password = bundle.getString("Password");
    }

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

    newUnitStatusContext = getContext();
    newUnitStatusActivity = getActivity();

    statusSpinner = view.findViewById(R.id.Status);
    generalCauseSpinner = view.findViewById(R.id.GeneralCause);
    newUSComment = view.findViewById(R.id.NewComment);
    newUnitStatusImage = view.findViewById(R.id.AddPhoto);
    addPhotoBtn = view.findViewById(R.id.AddPhotosLabel);
    addNewUnitStatus = view.findViewById(R.id.addBtnNewUnitStatus);

    ArrayAdapter<CharSequence> statusSpinnerAdapter = ArrayAdapter.createFromResource(newUnitStatusContext,
            R.array.new_unit_status_array, android.R.layout.simple_spinner_item);

    statusSpinnerAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
    statusSpinner.setAdapter(statusSpinnerAdapter);

    newUnitStatus = statusSpinner.getSelectedItem().toString();

    ArrayAdapter<CharSequence> generalCauseSpinnerAdapter = ArrayAdapter.createFromResource(newUnitStatusContext,
            R.array.status_general_cause_array, android.R.layout.simple_spinner_item);

    generalCauseSpinnerAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
    generalCauseSpinner.setAdapter(generalCauseSpinnerAdapter);

    generalCause = generalCauseSpinner.getSelectedItem().toString();

    addPhotoBtn.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View view) {
                startGallery();
        }
    });

    // Set a click listener for the text view
    addNewUnitStatus.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View view) {

            newUnitStatus = statusSpinner.getSelectedItem().toString();
            generalCause = generalCauseSpinner.getSelectedItem().toString();
            newUnitStatusComment = newUSComment.getText().toString();

            Toast.makeText(newUnitStatusContext, "SV: " +SearchValue + " US: " + newUnitStatus + " GC: " + generalCause + " USC: " + newUnitStatusComment + " User: " + LexaUser + " PW: " + Password, Toast.LENGTH_LONG).show();

            //addNewUnitStatus(SearchValue, newUnitStatus, generalCause, newUnitStatusComment, newUnitStatusPhoto, LexaUser, Password);

        }
    });

    return view;
}

感谢所有帮助！谢谢！

【问题讨论】：

你确定吗，在为新片段创建实例之前，你已经填充了变量SearchValue, LexaUser, Password, QA。如果您在该活动中没有收到来自该 Bundle 的变量怎么办？
对不起，我没有将它包含在我的代码中，但我实际上调用了一个名为 getUnitDetails() 的函数，它使用相同的值，并且工作正常......
在 IDE 中的 fragment.setArguments(connBundle) 处放置一个断点；调试并遍历它并检查捆绑包是否正确传递。
活动中的变量分配是否正确？你调试了吗？
到目前为止，我已经完成了打开片段的调试步骤。我可以在我的 UnitActivity 类中看到我的变量，但它们对于片段本身保持为空。

标签： android android-fragments android-bundle

【解决方案1】：

对于其他答案，您可以尝试以下方法：

bottomNavigation.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
            @Override
            public boolean onNavigationItemSelected(@NonNull MenuItem item) {
                int id = item.getItemId();

                Bundle connBundle = new Bundle();
                connBundle.putString("SearchValue", SearchValue);
                connBundle.putString("LexaUser", LexaUser);
                connBundle.putString("Password", Password);
                connBundle.putString("QA", QA);

                switch (id){
                    case R.id.action_search:
                        fragment = new NewUnitStatusFragment(connBundle);
                        break;
                    case R.id.action_cart:
                        fragment = new PendingUnitStatusFragment(connBundle);
                        break;
                    case R.id.action_hot_deals:
                        fragment = new FinalUnitStatusFragment(connBundle);
                        break;
                    case R.id.action_siblings:
                        fragment = new SiblingUnitFragment(connBundle);
                        break;
                }

                final FragmentTransaction transaction = fragmentManager.beginTransaction();
                transaction.replace(R.id.main_container, fragment).commit();

                return true;
            }
        });

在您的 Fragment 中，您从传递的捆绑参数中获取参数，例如：

private Bundle bundle;

    public static FragmentA(Bundle bundle) {
        this.bundle = bundle;
    }

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

    if (bundle != null) {
        SearchValue = bundle.getString("SearchValue");
        LexaUser = bundle.getString("LexaUser");
        Password = bundle.getString("Password");
    }

    //etc...
}

【讨论】：