无法在会话中使用SharedPreferences存储字符串android

我想在启动屏幕上存储城市名称，使用Geocoder获取城市名称后，我试图将其存储在会话中，并将其用于其他活动。但是，添加会话对象后，应用程序正在崩溃。无法在会话中使用SharedPreferences存储字符串android

下面

是我session.java

import android.content.Context; 
import android.content.SharedPreferences; 
import android.preference.PreferenceManager; 

import java.security.PublicKey; 
import java.util.HashMap; 


public class Session { 
    private SharedPreferences sp; 
    private SharedPreferences.Editor spEditor; 

public Session(Context context) { 
     sp = PreferenceManager.getDefaultSharedPreferences(context); 

    } 

public void setLocation(String city){ 
     spEditor.putString("UserCity", city); 
     spEditor.commit(); 
    }

和我SplashActivity.java

import android.animation.ObjectAnimator; 
import android.annotation.SuppressLint; 
import android.annotation.TargetApi; 
import android.content.DialogInterface; 
import android.content.Intent; 
import android.content.pm.PackageManager; 
import android.graphics.Typeface; 
import android.location.Address; 
import android.location.Geocoder; 
import android.os.Build; 
import android.os.Bundle; 
import android.os.Handler; 
import android.support.v7.app.AlertDialog; 
import android.support.v7.app.AppCompatActivity; 
import android.view.Window; 
import android.view.WindowManager; 
import android.view.animation.Animation; 
import android.view.animation.AnimationUtils; 
import android.widget.ImageView; 
import android.widget.TextView; 
import android.widget.Toast; 

import java.io.IOException; 
import java.util.ArrayList; 
import java.util.List; 
import java.util.Locale; 

import zesteve.com.myapplication.location.LocationTrack; 

import static android.Manifest.permission.ACCESS_COARSE_LOCATION; 
import static android.Manifest.permission.ACCESS_FINE_LOCATION; 


public class SplashActivity extends AppCompatActivity { 

    TextView welcomeText; 
    ImageView mLogo; 
    ImageView zbgimg; 

    Typeface tf1; 

    private Session session; 

    private ArrayList<String> permissionsToRequest; 
    private ArrayList<String> permissionsRejected = new ArrayList<>(); 
    private ArrayList<String> permissions = new ArrayList<>(); 

    private final static int ALL_PERMISSIONS_RESULT = 101; 
    LocationTrack locationTrack; 


    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     requestWindowFeature(Window.FEATURE_NO_TITLE); 
     getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, 
       WindowManager.LayoutParams.FLAG_FULLSCREEN); 

     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_splash); 

     session = new Session(SplashActivity.this); 

     //GPS Tracker 
     permissions.add(ACCESS_FINE_LOCATION); 
     permissions.add(ACCESS_COARSE_LOCATION); 

     permissionsToRequest = findUnAskedPermissions(permissions); 
     //get the permissions we have asked for before but are not granted.. 
     //we will store this in a global list to access later. 

     if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) { 
      if (permissionsToRequest.size() > 0) 
       requestPermissions(permissionsToRequest.toArray(new String[permissionsToRequest.size()]), ALL_PERMISSIONS_RESULT); 
     } 

     locationTrack = new LocationTrack(SplashActivity.this); 

     if (locationTrack.canGetLocation()) { 
      double longitude = locationTrack.getLongitude(); 
      double latitude = locationTrack.getLatitude(); 

      Geocoder gcd = new Geocoder(SplashActivity.this, Locale.getDefault()); 
      List<Address> addresses = null; 
      try { 
       addresses = gcd.getFromLocation(latitude, longitude, 1); 
      } catch (IOException e) { 
       e.printStackTrace(); 
      } 
      if (addresses != null && addresses.size() > 0) { 
       String locality = addresses.get(0).getLocality(); 
       String address = addresses.get(0).getAddressLine(0); 
       String state = addresses.get(0).getAdminArea(); 
       String countryn = addresses.get(0).getCountryName(); 
       String postalCode = addresses.get(0).getPostalCode(); 
       String knownName = addresses.get(0).getFeatureName(); 


       session.setLocation(locality); 

       //Toast.makeText(SplashActivity.this,locality +" "+ postalCode + " " + latitude+ " " + longitude,Toast.LENGTH_SHORT).show(); 
      } 
     } else { 
      locationTrack.showSettingsAlert(); 
     } 

     welcomeText = (TextView) findViewById(R.id.welcome); 
     tf1 = Typeface.createFromAsset(getAssets(), "fonts/Roboto-Light.ttf"); 
     welcomeText.setTypeface(tf1); 
     mLogo = (ImageView) findViewById(R.id.applogo); 
     zbgimg = (ImageView) findViewById(R.id.zbgimg); 
     zbgimg.setImageResource(R.drawable.splash_screen_option_three); 


     animation2(); 
     animation3(); 

     new Handler().postDelayed(new Runnable() { 

      @SuppressLint("PrivateResource") 
      @Override 
      public void run() { 
       if (session.FbLoggedIn()) { 
        Intent i = new Intent(SplashActivity.this, 
          MainActivity.class); 
        startActivity(i); 
        finish(); 
        overridePendingTransition(R.anim.entry, R.anim.exit); 
       } else { 
        Intent i = new Intent(SplashActivity.this, 
          LoginActivity.class); 
        startActivity(i); 
        finish(); 
        overridePendingTransition(R.anim.entry, R.anim.exit); 
       } 

      } 

     }, 3000); 
    } 


    private void animation2() { 
     mLogo.setAlpha(1.0F); 
     Animation anim = AnimationUtils.loadAnimation(SplashActivity.this, R.anim.translate_top_to_center); 
     mLogo.startAnimation(anim); 
    } 

    private void animation3() { 
     ObjectAnimator alphaAnimation = ObjectAnimator.ofFloat(welcomeText, "alpha", 0.0F, 1.0F); 
     alphaAnimation.setStartDelay(1700); 
     alphaAnimation.setDuration(500); 
     alphaAnimation.start(); 
    } 


    ///GPS Tracker 
    private ArrayList<String> findUnAskedPermissions(ArrayList<String> wanted) { 
     ArrayList<String> result = new ArrayList<String>(); 

     for (String perm : wanted) { 
      if (!hasPermission(perm)) { 
       result.add(perm); 
      } 
     } 

     return result; 
    } 

    private boolean hasPermission(String permission) { 
     if (canMakeSmores()) { 
      if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) { 
       return (checkSelfPermission(permission) == PackageManager.PERMISSION_GRANTED); 
      } 
     } 
     return true; 
    } 

    private boolean canMakeSmores() { 
     return (Build.VERSION.SDK_INT > Build.VERSION_CODES.LOLLIPOP_MR1); 
    } 


    @TargetApi(Build.VERSION_CODES.M) 
    @Override 
    public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) { 

     switch (requestCode) { 

      case ALL_PERMISSIONS_RESULT: 
       for (String perms : permissionsToRequest) { 
        if (!hasPermission(perms)) { 
         permissionsRejected.add(perms); 
        } 
       } 

       if (permissionsRejected.size() > 0) { 


        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) { 
         if (shouldShowRequestPermissionRationale(permissionsRejected.get(0))) { 
          showMessageOKCancel("These permissions are mandatory for the application. Please allow access.", 
            new DialogInterface.OnClickListener() { 
             @Override 
             public void onClick(DialogInterface dialog, int which) { 
              if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) { 
               requestPermissions(permissionsRejected.toArray(new String[permissionsRejected.size()]), ALL_PERMISSIONS_RESULT); 
              } 
             } 
            }); 
          return; 
         } 
        } 

       } 

       break; 
     } 

    } 

    private void showMessageOKCancel(String message, DialogInterface.OnClickListener okListener) { 
     new AlertDialog.Builder(SplashActivity.this) 
       .setMessage(message) 
       .setPositiveButton("OK", okListener) 
       .setNegativeButton("Cancel", null) 
       .create() 
       .show(); 
    } 

    @Override 
    protected void onDestroy() { 
     super.onDestroy(); 
     locationTrack.stopListener(); 
    } 


}

我可以看到在

Toast.makeText(SplashActivity.this,locality +" "+ postalCode + " " + latitude+ " " + longitude,Toast.LENGTH_SHORT).show();

城市的名字，但无法储存它在会议中。我的session.jave与其他活动正常工作。波纹管是logcat的：

05-11 22:36:15.966 3836-3836/ 
zesteve.com.myapplication E/AndroidRuntime: 
FATAL EXCEPTION: main 
Process: zesteve.com.myapplication, PID: 3836 
java.lang.RuntimeException: 
Unable to start activity ComponentInfo 
{zesteve.com.myapplication/zesteve.com.myapplication.SplashActivity}: 
java.lang.NullPointerException: Attempt to invoke interface method 
android.content.SharedPreferences$Editor 
android.content.SharedPreferences 
$Editor.putString(java.lang.String, 
java.lang.String) 
on a null object reference 
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2439) 
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2499)                      at android.app.ActivityThread.access$900(ActivityThread.java:166) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1360) 
at android.os.Handler.dispatchMessage(Handler.java:102) 
at android.os.Looper.loop(Looper.java:148) 
at android.app.ActivityThread.main(ActivityThread.java:5468) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run 
(ZygoteInit.java:726) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) 

Caused by: java.lang.NullPointerException: 
Attempt to invoke interface method android.content.SharedPreferences$Editor 
android.content.SharedPreferences$Editor.putString(java.lang.String, java.lang.String) 
on a null object reference 

at zesteve.com.myapplication.Session.setLocation(Session.java:71) 
at zesteve.com.myapplication.SplashActivity.onCreate(SplashActivity.java:100) 
at android.app.Activity.performCreate(Activity.java:6556) 
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1108) 
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2392) 
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2499) 
at android.app.ActivityThread.access$900(ActivityThread.java:166) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1360) 
at android.os.Handler.dispatchMessage(Handler.java:102) 
at android.os.Looper.loop(Looper.java:148) 
at android.app.ActivityThread.main(ActivityThread.java:5468) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

来源

2017-05-11 Asesha George

你错过了创建Editor对象，这就是为什么你得到空指针把这条线spEditor = sp.edit（）在你的会话construtor –

是的sandeep感谢您的快速回复。 –

Geordge欢迎亲爱的 –

你不会被初始化偏好编辑器，你必须进行以下

public void setLocation(String city){ 
     spEditor=sp.edit();//// make sure sp also initialized 
     spEditor.putString("UserCity", city); 
     spEditor.commit(); 
    }

来源

2017-05-11 17:39:11 Pavan

你spEditor变量是空的变化，因为你不把它初始化到任何东西。

试试你的session.java构造函数。

public Session(Context context) { 
    sp = PreferenceManager.getDefaultSharedPreferences(context); 
    spEditor = sp.edit(); 
}

来源

2017-05-11 17:40:52 Kia

是的，我明白了。现在它的工作......对不起，我已经接受了下面的同样的答案 –

检查变量SharedPreferences.Editor spEditor;所有的字段都被初始化。检查你的setter方法。

来源

2017-05-11 17:55:16

无法在会话中使用SharedPreferences存储字符串android

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