Android - 来自 AlertDialog 的字符串值在访问时不断重置

Posted 2023-03-22

【中文标题】Android - 来自 AlertDialog 的字符串值在访问时不断重置

【英文标题】：Android - String value from AlertDialog keeps resetting on access

【发布时间】：2017-03-19 17:54:21

【问题描述】：

我遇到了一个问题，即使我在 AlertDialog Fragment 中为它输入了数据，我也将数据输入到我的字符串一直重置为 null 的位置。假设我将数据输入到 EditText 对象中，将其存储在字符串变量中，将其设置为我的 Getter/Setter 类中的字符串值，然后在我的片段中从该类中检索。

AlertDialog 的图片

AlertDialog 片段

import android.app.AlertDialog;
import android.app.Dialog;
import android.app.DialogFragment;
import android.content.DialogInterface;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.EditText;

import org.ramferno.scoutapplication.ramfernoscout.R;
import org.ramferno.scoutapplication.ramfernoscout.providers.AddressProvider;

public class AddressDialogFragment extends DialogFragment 
    AddressProvider addressProvider = new AddressProvider();
    EditText enterIP;
    String urlAddress;

    @Override
    public Dialog onCreateDialog(Bundle savedInstanceState) 
        //Declare and initialize objects
        LayoutInflater i = getActivity().getLayoutInflater();
        View v = i.inflate(R.layout.fragment_dialog, null);
        enterIP = (EditText) v.findViewById(R.id.enterIP);

        //Create AlertDialog
        AlertDialog.Builder b = new AlertDialog.Builder(getActivity())
                .setTitle("Enter IP Address")
                .setPositiveButton("ADD",
                        new DialogInterface.OnClickListener() 
                           public void onClick(DialogInterface dialog, int whichButton) 
                                urlAddress = enterIP.getText().toString();
                                addressProvider.setAddress(urlAddress);
                             //End of onClick
                        ) //End of DialogInterface
                .setNegativeButton("Cancel",
                        new DialogInterface.OnClickListener() 
                           public void onClick(DialogInterface dialog, int whichButton) 
                                dialog.cancel();
                             //End of onClick
                         //End of DialogInterface
                ); //End of AlertDialog
        b.setView(v);
        return b.create();
     //End of onCreateDialog
 //End of class

Getter/Setter 类

public class AddressProvider 
    private String urlAddress;

    public String getAddress() 
        return urlAddress;
     //End of getAddress

    public void setAddress(String urlAddress) 
        this.urlAddress = urlAddress;
     //End of setAddress
 //End of class

ScoutFragment（从 Getter/Setter 接收字符串的片段）

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

import org.ramferno.scoutapplication.ramfernoscout.downloaders.Downloader;
import org.ramferno.scoutapplication.ramfernoscout.R;
import org.ramferno.scoutapplication.ramfernoscout.providers.AddressProvider;

//Start of ScoutFragment
public class ScoutFragment extends Fragment 
    //Declares Android UI objects
    AddressProvider addressProvider = new AddressProvider();
    FloatingActionButton addDataScout;
    ListView eListScoutInfo;
    String IP = addressProvider.getAddress();

    //Declare and initialize variable
    String urlAddress = "http://" + IP + "/ramfernoscout/matchdb/matchretrieve.php";

    public ScoutFragment() 
        // Required empty public constructor
     //End of ScoutFragment

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) 
        //Inflates layout for this fragment
        View view = inflater.inflate(R.layout.fragment_scout, null, false);

        //Instantiate ListView object with the xml ListView object
        eListScoutInfo = (ListView) view.findViewById(R.id.listScoutInfo);

        //Add instructions to the Refresh FAB that will download the data from the database server
        FloatingActionButton fab = (FloatingActionButton) view.findViewById(R.id.fab2);
        fab.setOnClickListener(new View.OnClickListener() 
            @Override
            public void onClick(View view) 
                Downloader d = new Downloader(getActivity(),urlAddress,eListScoutInfo);
                d.execute();
             //End of onClick
        ); //End  of setOnClickListener

        //Change fragment to AddScoutDataFragment with animations
        addDataScout = (FloatingActionButton) view.findViewById(R.id.fab);
        addDataScout.setOnClickListener(new View.OnClickListener() 
            public void onClick(View v) 
                AddScoutDataFragment fragment = new AddScoutDataFragment();
                FragmentTransaction fragmentTransaction = getFragmentManager().beginTransaction();
                fragmentTransaction.setCustomAnimations(R.anim.enter_from_right,
                        R.anim.exit_to_left, R.anim.enter_from_left, R.anim.exit_to_right);
                fragmentTransaction.replace(R.id.fragment_container, fragment);
                fragmentTransaction.commit();
             //End of onClick
        ); //End of setOnClickListener

        //Returns view
        return view;
     //End of onCreateView
 //End of class

【参考方案1】：

您在ScoutFragment 和AddressDialogFragment 中都使用AddressProvider addressProvider = new AddressProvider();。

new 运算符将创建AddressProvider 类的新实例。如果你想持久化数据，你应该只创建一个AddressProvider 的实例。所以你应该将AddressProvider 设为SingleTon 类。

public class AddressProvider 
    private static AddressProvider ourInstance = new AddressProvider();
    private String urlAddress;

    private AddressProvider() 
    

    public static AddressProvider getInstance() 
        return ourInstance;
    

    public String getAddress() 
        return urlAddress;
    

    public void setAddress(String urlAddress) 
        this.urlAddress = urlAddress;
    

用法，

要存储 IP，

AddressProvider.getInstance().setAddress("xxx.xxx.xx.xx");

检索，

AddressProvider.getInstance().getAddress()