Démarrage d'une activité montre Android - NullPointerException: stockage == null

Question

J'ai une application dans laquelle une activité est lancée montre une exception nullpointer, mais je ne peux pas comprendre ce que l'erreur est et où je me trompe. Je suis nouveau à Android et je serais reconnaissant si vous pouviez aider. Merci à advance.`

C'est l'activité qui montre l'erreur lors du démarrage AccountsActivity.java

public class AccountsActivity extends AppCompatActivity { 

SharedPreferences myPrefs = PreferenceManager.getDefaultSharedPreferences(OpeningScreenActivity.getContextOfApplication()); 
String token = myPrefs.getString("GCMTOKEN", ""); 
String JSON_URL = "http://xyz.in/view_json.php?device_id=" + token; 

private ListView listView; 
/** 
* ATTENTION: This was auto-generated to implement the App Indexing API. 
* See https://g.co/AppIndexing/AndroidStudio for more information. 
*/ 
private GoogleApiClient client; 

@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_accounts); 
    listView = (ListView) findViewById(R.id.listView); 

    sendRequest(); 
    // ATTENTION: This was auto-generated to implement the App Indexing API. 
    // See https://g.co/AppIndexing/AndroidStudio for more information. 
    client = new GoogleApiClient.Builder(this).addApi(AppIndex.API).build(); 
} 

private void sendRequest() { 
    StringRequest stringRequest = new StringRequest(JSON_URL, 
      new Response.Listener<String>() { 
       @Override 
       public void onResponse(String response) { 
        showJSON(response); 
       } 
      }, 
      new Response.ErrorListener() { 
       @Override 
       public void onErrorResponse(VolleyError error) { 
        Toast.makeText(AccountsActivity.this, error.getMessage(), Toast.LENGTH_LONG).show(); 
       } 
      }); 
    RequestQueue requestQueue = Volley.newRequestQueue(this); 
    requestQueue.add(stringRequest); 
} 



private void showJSON(String json) { 
    ParseJSON pj = new ParseJSON(json); 
    pj.parseJSON(); 
    CustomList cl = new CustomList(this, ParseJSON.ids,ParseJSON.mem_codes,ParseJSON.created_ons); 
    listView.setAdapter(cl); 
} 
} 

Cette classe est ParseJSON.java

public class AccountsActivity extends AppCompatActivity { 

SharedPreferences myPrefs = PreferenceManager.getDefaultSharedPreferences(OpeningScreenActivity.getContextOfApplication()); 
String token = myPrefs.getString("GCMTOKEN", ""); 
String JSON_URL = "http://sovran.in/sov2fa_v2/view_json.php?device_id=" + token; 

private ListView listView; 
/** 
* ATTENTION: This was auto-generated to implement the App Indexing API. 
* See https://g.co/AppIndexing/AndroidStudio for more information. 
*/ 
private GoogleApiClient client; 

@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_accounts); 
    listView = (ListView) findViewById(R.id.listView); 

    sendRequest(); 
    // ATTENTION: This was auto-generated to implement the App Indexing API. 
    // See https://g.co/AppIndexing/AndroidStudio for more information. 
    client = new GoogleApiClient.Builder(this).addApi(AppIndex.API).build(); 
} 

private void sendRequest() { 
    StringRequest stringRequest = new StringRequest(JSON_URL, 
      new Response.Listener<String>() { 
       @Override 
       public void onResponse(String response) { 
        showJSON(response); 
       } 
      }, 
      new Response.ErrorListener() { 
       @Override 
       public void onErrorResponse(VolleyError error) { 
        Toast.makeText(AccountsActivity.this, error.getMessage(), Toast.LENGTH_LONG).show(); 
       } 
      }); 
    RequestQueue requestQueue = Volley.newRequestQueue(this); 
    requestQueue.add(stringRequest); 
} 



private void showJSON(String json) { 
    ParseJSON pj = new ParseJSON(json); 
    pj.parseJSON(); 
    CustomList cl = new CustomList(this, ParseJSON.ids,ParseJSON.mem_codes,ParseJSON.created_ons); 
    listView.setAdapter(cl); 
} 
} 

C'est CustomList.java

public class CustomList extends ArrayAdapter<String> { 
private String[] ids; 
private String[] mem_codes; 
private String[] created_ons; 
private Activity context; 



public CustomList(Activity context, String[] ids, String[] mem_codes, String[] created_ons) { 
    super(context, R.layout.list_view_layout, ids); 
    this.context = context; 
    this.ids = ids; 
    this.mem_codes = mem_codes; 
    this.created_ons = created_ons; 


} 

@Override 
public View getView(int position, View convertView, ViewGroup parent) { 
    LayoutInflater inflater = context.getLayoutInflater(); 
    View listViewItem = inflater.inflate(R.layout.list_view_layout, null, true); 
    TextView textViewId = (TextView) listViewItem.findViewById(R.id.textViewId); 
    TextView textViewMemCode = (TextView) listViewItem.findViewById(R.id.textViewMem_code); 
    TextView textViewCreatedOn = (TextView) listViewItem.findViewById(R.id.textViewCreated_on); 
    textViewId.setText(ids[position]); 
    textViewMemCode.setText(mem_codes[position]); 
    textViewCreatedOn.setText(created_ons[position]); 
    return listViewItem; 
} 


} 

Et ceci est le journal des erreurs

07-15 14:04:46.269 32255-32255/com.sovran.sov2fa E/AndroidRuntime: FATAL EXCEPTION: main 
                   Process: com.sovran.sov2fa, PID: 32255 
                   java.lang.ExceptionInInitializerError 
                    at java.lang.reflect.Constructor.newInstance(Native Method) 
                    at java.lang.Class.newInstance(Class.java:1606) 
                    at android.app.Instrumentation.newActivity(Instrumentation.java:1071) 
                    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416) 
                    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2614) 
                    at android.app.ActivityThread.access$800(ActivityThread.java:178) 
                    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1470) 
                    at android.os.Handler.dispatchMessage(Handler.java:111) 
                    at android.os.Looper.loop(Looper.java:194) 
                    at android.app.ActivityThread.main(ActivityThread.java:5653) 
                    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:960) 
                    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:755) 
                   Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.content.Context.getPackageName()' on a null object reference 
                    at android.preference.PreferenceManager.getDefaultSharedPreferencesName(PreferenceManager.java:383) 
                    at android.preference.PreferenceManager.getDefaultSharedPreferences(PreferenceManager.java:378) 
                    at com.sovran.sov2fa.AccountsActivity.<clinit>(AccountsActivity.java:20) 
                    at java.lang.reflect.Constructor.newInstance(Native Method)  
                    at java.lang.Class.newInstance(Class.java:1606)  
                    at android.app.Instrumentation.newActivity(Instrumentation.java:1071)  
                    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416)  
                    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2614)  
                    at android.app.ActivityThread.access$800(ActivityThread.java:178)  
                    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1470)  
                    at android.os.Handler.dispatchMessage(Handler.java:111)  
                    at android.os.Looper.loop(Looper.java:194)  
                    at android.app.ActivityThread.main(ActivityThread.java:5653)  
                    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:960)  
                    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:755)  

Answer 1

Est-ce que l'initialisation de votre attribut myPrefs au sein onCreate() -method

@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_accounts); 
    myPrefs = PreferenceManager.getDefaultSharedPreferences(this); 
    ... 
}