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

Question

我遇到了一个问题，即使我在 AlertDialog fragment 中输入了数据，我输入的数据仍然重置为 null。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，然后从 fragment 中的该类中检索。

AlertDialog 图像

AlertDialog fragment

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 fragment )

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

Answer 1

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

new 运算符将创建 AddressProvider 类的新实例。如果您想保留数据，您应该只创建一个 AddressProvider 实例。所以你应该将 AddressProvider 设置为 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;
    }
}

使用情况，

存储IP，

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

检索，

AddressProvider.getInstance().getAddress()