Error getting SharedPreferences

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Error getting SharedPreferences

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#1 by (5 votes)

1

I'm trying to create a class to get the predefined data, but when I call the method Load() the app stops. Could you help me? Thanks

package com.example.nano.prueba.login.loginprueba;

import android.content.Context;
import android.content.SharedPreferences;
import android.support.v7.app.AppCompatActivity;


/**
 * Created by admin on 02/04/2016.
 */
public class LoadPreferencias extends AppCompatActivity {

    private String User;
    private String Pass;

    public void Load(){

        SharedPreferences Preferencias = getSharedPreferences("DatosUser", Context.MODE_PRIVATE);
        User =(Preferencias.getString("User",""));
        Pass = (Preferencias.getString("Pass", ""));

    }

    public String GetUser()
    {
        Load();
        return User;
    }
    public String GetPass()
    {
        return Pass;
    }



}

I add error code

04-03 09: 55: 44.445 31786-31786 /? E / AndroidRuntime: FATAL EXCEPTION: main Process: com.example.nano.prueba.login.logintest, PID: 31786 java.lang.RuntimeException: Unable to start activity ComponentInfo {com.example.nano.test.login.logintest / com.example.nano.test.login.logintest.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.SharedPreferences android.content.Context.getSharedPreferences (java.lang.String, int) ' on a null object reference at android.app.ActivityThread.performLaunchActivity (ActivityThread.java:2658) at android.app.ActivityThread.handleLaunchActivity (ActivityThread.java:2723) at android.app.ActivityThread.access $ 900 (ActivityThread.java:172) at android.app.ActivityThread $ H.handleMessage (ActivityThread.java:1422) at android.os.Handler.dispatchMessage (Handler.java:102) at android.os.Looper.loop (Looper.java:145) at android.app.ActivityThread.main (ActivityThread.java:5832) at java.lang.reflect.Method.invoke (Native Method) at java.lang.reflect.Method.invoke (Method.java:372) at com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run (ZygoteInit.java:1399) at com.android.internal.os.ZygoteInit.main (ZygoteInit.java:1194) Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.SharedPreferences android.content.Context.getSharedPreferences (java.lang.String, int) ' on a null object reference at android.content.ContextWrapper.getSharedPreferences (ContextWrapper.java:184) at com.example.nano.test.login.logintest.LoadPref.Load (LoadPref.java:16) at com.example.nano.test.login.logintest.MainActivity.onCreate (MainActivity.java:41) at android.app.Activity.performCreate (Activity.java:6221) at android.app.Instrumentation.callActivityOnCreate (Instrumentation.java:1119) at android.app.ActivityThread.performLaunchActivity (ActivityThread.java:2611) at android.app.ActivityThread.handleLaunchActivity (ActivityThread.java:2723) at android.app.ActivityThread.access $ 900 (ActivityThread.java:172) at android.app.ActivityThread $ H.handleMessage (ActivityThread.java:1422) at android.os.Handler.dispatchMessage (Handler.java:102) at android.os.Looper.loop (Looper.java:145) at android.app.ActivityThread.main (ActivityThread.java:5832) at java.lang.reflect.Method.invoke (Native Method) at java.lang.reflect.Method.invoke (Method.java:372) at com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run (ZygoteInit.java:1399) at com.android.internal.os.ZygoteInit.main (ZygoteInit.java:1194)

java android

asked by Alejandro Echeverria 03.04.2016 в 01:40

source

1 answer

How can I connect a view and a controller [closed] Concatenate two dictionaries without repeating field

score 5 · Accepted Answer

According to your error message:

android.content.Context.getSharedPreferences ComponentInfo {com.example.nano.test.login.logintest / com.example.nano.test.login.logintest.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.SharedPreferences android.content. Context.getSharedPreferences

You are calling the Load () method from MainActivity, the Load () method needs to receive the Context, so the error! Modify your method to receive it:

   public void Load(Context context){

    SharedPreferences Preferencias = context.getSharedPreferences("DatosUser", Context.MODE_PRIVATE);
    User =(Preferencias.getString("User",""));
    Pass = (Preferencias.getString("Pass", ""));

}

Although a better design would be to create 2 methods that you call when you need the User or Pass values, your class LoadPreferencias does not need to extend AppCompatActivity , and here you can add the methods to save the values, setUser() and setPass() :

public class LoadPreferencias {

    public static String GetUser(Context context)
    {
     SharedPreferences Preferencias = context.getSharedPreferences("DatosUser", Context.MODE_PRIVATE);
    String   User =Preferencias.getString("User","");
        return User;
    }


    public static String GetPass(Context context)
    {
      SharedPreferences Preferencias = context.getSharedPreferences("DatosUser", Context.MODE_PRIVATE);
    String   Pass =Preferencias.getString("Pass","");
        return Pass;
    }  
}

From MainActivity you would choose the methods in this way:

String usuario = LoadPreferencias.GetUser(getApplicationContext());
String password = LoadPreferencias.GetPass(getApplicationContext());