java - android:SharedPreferences不保存数据

Question

我制作了一个小型Android应用程序，从 ListView 中打开谷歌地图 Activity ，当您长按 map 时，它会将该位置的地址保存在ArrayList中，然后将其添加到 ListView 中，该位置的纬度和经度也以这种方式保存，然后我通过SharedPreferences保存所有这些信息。 我的问题是，即使 ListView 在应用程序运行时更新，但当我重新启动应用程序时，我会丢失所有数据，基本上意味着信息永远不会被保存。 数据的保存是在 MapsActivity 中的 onMapLongClick 方法中完成的，数据加载是在 MainActivity 中的 OnCreate 方法中完成的。

主要 Activity :

package com.rapha.favoriteplaces;

import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import java.io.IOException;
import java.util.ArrayList;

public class MainActivity extends AppCompatActivity {
    static ArrayList<String> places = new ArrayList<>();
    static ArrayList<String> lats = new ArrayList<>();
    static ArrayList<String> lngs = new ArrayList<>();
    static ArrayAdapter arrayAdapter;

    @Override
    public void onBackPressed()
    {

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

        ListView listView = (ListView)findViewById(R.id.list);

        places.add("Add a location...");

        final Intent intent = new Intent(getApplicationContext(), MapsActivity.class);

        SharedPreferences sharedPreferences = this.getSharedPreferences("package com.rapha.favoriteplaces", Context.MODE_PRIVATE);

        try {
            places = (ArrayList<String>) ObjectSerializer.deserialize(sharedPreferences.getString("places", ObjectSerializer.serialize(new ArrayList<String>())));

            lats = (ArrayList<String>)ObjectSerializer.deserialize(sharedPreferences.getString("lats", ObjectSerializer.serialize(new ArrayList<String>())));
            lngs = (ArrayList<String>)ObjectSerializer.deserialize(sharedPreferences.getString("lngs", ObjectSerializer.serialize(new ArrayList<String>())));
        } catch (IOException e) {
            e.printStackTrace();
        }

        if(places.size() > 0 && lats.size() > 0 && lngs.size() > 0)
        {
            System.out.println("load data sucessfully check");
        }

        arrayAdapter = new ArrayAdapter(this, android.R.layout.simple_list_item_1, places);
        listView.setAdapter(arrayAdapter);

        listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {

            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {

                if(position == 0)
                {
                    intent.putExtra("coisa", position);
                    startActivity(intent);
                }
                else
                {
                    intent.putExtra("coisa", position);
                    String lat = ((lats.get(position - 1)));
                    String lon = ((lngs.get(position - 1)));
                    intent.putExtra("lat", lat);
                    intent.putExtra("lon", lon);
                    intent.putExtra("ad", places.get(position));

                    startActivity(intent);
                }
            }
        });
    }
}

map Activity :

package com.rapha.favoriteplaces;

import android.*;
import android.Manifest;
import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.content.pm.PackageManager;
import android.location.Address;
import android.location.Geocoder;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.net.Uri;
import android.os.Build;
import android.os.Handler;
import android.support.annotation.NonNull;
import android.support.v4.app.ActivityCompat;
import android.support.v4.app.FragmentActivity;
import android.os.Bundle;
import android.support.v4.content.ContextCompat;
import android.util.Log;
import android.view.GestureDetector;
import android.view.MotionEvent;
import android.widget.Toast;
import com.google.android.gms.appindexing.Action;
import com.google.android.gms.appindexing.AppIndex;
import com.google.android.gms.appindexing.Thing;
import com.google.android.gms.common.api.GoogleApiClient;
import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.OnMapReadyCallback;
import com.google.android.gms.maps.SupportMapFragment;
import com.google.android.gms.maps.model.BitmapDescriptorFactory;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.Marker;
import com.google.android.gms.maps.model.MarkerOptions;
import java.io.IOException;
import java.util.List;
import java.util.Locale; 

public class MapsActivity extends FragmentActivity implements  OnMapReadyCallback, GoogleMap.OnMapLongClickListener {

    private GoogleMap mMap;
    LocationManager locationManager;
    LocationListener locationListener;
    String address;

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);

        if (grantResults.length > 0 && grantResults[0] != PackageManager.PERMISSION_GRANTED) {
            if (ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
                locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 5, 100000, locationListener);
            }
        }
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_maps);
        // Obtain the SupportMapFragment and get notified when the map is ready to be used.
        SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager()
                .findFragmentById(R.id.map);
        mapFragment.getMapAsync(this);
    }
    /**
     * Manipulates the map once available.
     * This callback is triggered when the map is ready to be used.
     * This is where we can add markers or lines, add listeners or move the camera. In this case,
     * we just add a marker near Sydney, Australia.
     * If Google Play services is not installed on the device, the user will be prompted to install
     * it inside the SupportMapFragment. This method will only be triggered once the user has
     * installed Google Play services and returned to the app.
     */
    @Override
    public void onMapReady(GoogleMap googleMap) {
        mMap = googleMap;

        Intent intent = getIntent();

        mMap.setOnMapLongClickListener(this);
        int coisa = intent.getIntExtra("coisa", 0);

        if(coisa == 0)
        {
            locationManager = (LocationManager) this.getSystemService(Context.LOCATION_SERVICE);

            locationListener = new LocationListener() {
                @Override
                public void onLocationChanged(Location location) {

                    LatLng userLocation = new LatLng(location.getLatitude(), location.getLongitude());

                    mMap.moveCamera(CameraUpdateFactory.newLatLngZoom(userLocation, 15));
                }

                @Override
                public void onStatusChanged(String provider, int status, Bundle extras) {

                }

                @Override
                public void onProviderEnabled(String provider) {

                }

                @Override
                public void onProviderDisabled(String provider) {

                }
            };
            if (Build.VERSION.SDK_INT < 23) {
                locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 100, locationListener);
            } else {
                if (ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
                    ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.ACCESS_FINE_LOCATION}, 1);
                } else {
                    locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 100, locationListener);
                    mMap.clear();
                    Location lastKnownLocation = locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);
                    LatLng userLocation = new LatLng(lastKnownLocation.getLatitude(), lastKnownLocation.getLongitude());
                    mMap.moveCamera(CameraUpdateFactory.newLatLngZoom(userLocation, 15));
                }
            }
        }
        else
        {
            double lat = Double.parseDouble(intent.getStringExtra("lat"));
            double lon = Double.parseDouble(intent.getStringExtra("lon"));
            LatLng location = new LatLng(lat, lon);

            mMap.addMarker(new MarkerOptions().position(location).title(intent.getStringExtra("ad")));
            mMap.moveCamera(CameraUpdateFactory.newLatLngZoom(location, 15));
        }
    }
    @Override
    public void onMapLongClick(LatLng latLng) {

        Geocoder geocoder = new Geocoder(getApplicationContext(), Locale.getDefault());
        try {
            List<Address> addresses = geocoder.getFromLocation(latLng.latitude, latLng.longitude, 1);

            if (addresses != null && addresses.size() > 0) {

                address = addresses.get(0).getAddressLine(0);
            }

        } catch (IOException e) {
            e.printStackTrace();
        }
        mMap.addMarker(new MarkerOptions().position(latLng).title(address));
        MainActivity.lats.add(String.valueOf(latLng.latitude));
        MainActivity.lngs.add(String.valueOf(latLng.longitude));
        MainActivity.places.add(address);
        MainActivity.arrayAdapter.notifyDataSetChanged();

        SharedPreferences sharedPreferences = getSharedPreferences("com.rapha.favoriteplaces",Context.MODE_PRIVATE);

        try {

            sharedPreferences.edit().putString("lats", ObjectSerializer.serialize(MainActivity.lats)).apply();
            sharedPreferences.edit().putString("lngs", ObjectSerializer.serialize(MainActivity.lngs)).apply();

            sharedPreferences.edit().putString("places", ObjectSerializer.serialize(MainActivity.places)).apply();

        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

对象序列化器类:

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;

public class ObjectSerializer {

    public static String serialize(Serializable obj) throws IOException {
        if (obj == null) return "";
        try {
            ByteArrayOutputStream serialObj = new ByteArrayOutputStream();
            ObjectOutputStream objStream = new ObjectOutputStream(serialObj);
            objStream.writeObject(obj);
            objStream.close();
            return encodeBytes(serialObj.toByteArray());
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }

    public static Object deserialize(String str) throws IOException {
        if (str == null || str.length() == 0) return null;
        try {
            ByteArrayInputStream serialObj = new ByteArrayInputStream(decodeBytes(str));
            ObjectInputStream objStream = new ObjectInputStream(serialObj);
            return objStream.readObject();
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }

    public static String encodeBytes(byte[] bytes) {
        StringBuffer strBuf = new StringBuffer();

        for (int i = 0; i < bytes.length; i++) {
            strBuf.append((char) (((bytes[i] >> 4) & 0xF) + ((int) 'a')));
            strBuf.append((char) (((bytes[i]) & 0xF) + ((int) 'a')));
        }

        return strBuf.toString();
    }

    public static byte[] decodeBytes(String str) {
        byte[] bytes = new byte[str.length() / 2];
        for (int i = 0; i < str.length(); i += 2) {
            char c = str.charAt(i);
            bytes[i / 2] = (byte) ((c - 'a') << 4);
            c = str.charAt(i + 1);
            bytes[i / 2] += (c - 'a');
        }
        return bytes;
    }
}

Answer 1

您似乎正在投入和获得两种不同的偏好。

从首选项获取时，您使用包 com.rapha.favoriteplaces:

SharedPreferences sharedPreferences = this.getSharedPreferences("package com.rapha.favoriteplaces", Context.MODE_PRIVATE);
try {
    places = (ArrayList<String>) ObjectSerializer.deserialize(sharedPreferences.getString("places", ObjectSerializer.serialize(new ArrayList<String>())));
    // ...

保存您使用的值时com.rapha.favoriteplaces:

SharedPreferences sharedPreferences = getSharedPreferences("com.rapha.favoriteplaces",Context.MODE_PRIVATE);
sharedPreferences.edit().putString("lats", ObjectSerializer.serialize(MainActivity.lats)).apply();

将它们设置为相同，然后尝试。