nullpointer when using shared prefference in no activity class

Question

so i am trying to use my shared prefference in a no activity class but i keep getting null pointer on my

private SharedPreferences setingPreferences = context.getSharedPreferences("Settings", Activity.MODE_PRIVATE);

how do i solve this?

 public class ConnectionClass
{
    Context context;
    private SharedPreferences setingPreferences = context.getSharedPreferences("Settings", Activity.MODE_PRIVATE);
    String ip;
    String classs = "net.sourceforge.jtds.jdbc.Driver";
    String db = "ISTABLocalDB";
    String un = "istab_wpf";
    String password = "istab_!234";
    @SuppressLint("NewApi")
    public Connection CONN() {
        ip = setingPreferences.getString("server", "");
        StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder()
                .permitAll().build();
        StrictMode.setThreadPolicy(policy);
        Connection conn = null;
        String ConnURL = null;
        try {
            Class.forName(classs);
            ConnURL = "jdbc:jtds:sqlserver://" + ip + ";"
                    + "databaseName=" + db + ";user=" + un + ";password="
                    + password + ";";
            conn = DriverManager.getConnection(ConnURL);
        } catch (SQLException se) {
            Log.e("ERRO", se.getMessage());
        } catch (ClassNotFoundException e) {
            Log.e("ERRO", e.getMessage());
        } catch (Exception e) {
            Log.e("ERRO", e.getMessage());
        }
        return conn;

how can that be a duplicate? as this is a nullpointer caused by a not initailized context to my sharedprefference and that one is just more a general question so is not helpfull at all and iknow what a nullpointer is — omini data, Aug 16 '16 at 18:49

score 2 · Answer 1 · answered Aug 16 '16 at 17:24

2

You are using context before initializing it. In you class constructor take context as argument and then initialize you preference Object.

answered Aug 16 '16 at 17:24

Nayan Srivastava

3,655
3
27
49

score 2 · Accepted Answer · answered Aug 16 '16 at 17:33

2

You need to initialize your context variable. One way would be to pass the context variable from the activity class to this non-activity class by defining a constructor in the ConnectionClass

public ConnectionClass (Context context)  
{
   this.context = context;

}

Wherever you are going to instantiate this class, instantiate it by passing the context from the calling class.

For example, if you are instantiating this from an activity class, you can do so by

ConnectionClass conn = new ConnectionClass(MyActivity.this.getApplicationContext());

answered Aug 16 '16 at 17:33

SoulRayder

5,072
6
47
93

so if i change out my `public class ConnectionClass { ` to `public ConnectionClass (Context context) { this.context = context; } ` then i get class or interface expected – omini data Aug 16 '16 at 17:47
Class is fine as it is, just add the constructor method to it. Then you can pass along the context variable to be assigned to your in-class context variable, thereby avoiding the null pointer exception. – SoulRayder Aug 16 '16 at 17:51
awesome that did the trick – omini data Aug 16 '16 at 18:05
Happy to help you out :) – SoulRayder Aug 17 '16 at 11:52

score 0 · Answer 3 · answered Aug 16 '16 at 17:34

0

You have to initialize context.

Get the context on the constructor like this:

Context context;
private SharedPreferences setingPreferences;

public ConnectionClass(Context context){
    this.context = context;
}

public Connection CONN() {
    setingPreferences = context.getSharedPreferences("Settings", Activity.MODE_PRIVATE);
    ip = setingPreferences.getString("server", "");

    ...

Or you can get context direct on the method that you're calling:

private SharedPreferences setingPreferences;

public Connection CONN(Context context) {
    setingPreferences = context.getSharedPreferences("Settings", Activity.MODE_PRIVATE);
    ip = setingPreferences.getString("server", "");

    ...

answered Aug 16 '16 at 17:34

Ricardo A.

685
2
8
35

that are giving me Error:(427, 53) error: method CONN in class ConnectionClass cannot be applied to given types; required: Context found: no arguments reason: actual and formal argument lists differ in length – omini data Aug 16 '16 at 17:40
I think you're not passing the parameter when you call CONN(), or you're passing a different type. You have to call like this: Connection c = connectionClass.CONN(context); You're calling the method in a activity class? – Ricardo A. Aug 16 '16 at 17:48
i getting Error:(427, 53) error: method CONN in class ConnectionClass cannot be applied to given types; required: Context found: no arguments reason: actual and formal argument lists differ in length on `try { Connection c = connectionClass.CONN‌(context); if (con == null) {` and it cannot resolve method and symbol – omini data Aug 16 '16 at 17:54
Well, this can be a lot of things, but I'll try to help. First, you need to have a context, if you're calling in a activity class you can pass like this: Context context = this; if you're not in a activity class you have to get in another way. Second, I think you're using wrong variable names, "c" and "con" is the same thing, isn't? If is you have to rename c to con or con to c. If the error persists tell me what IDE you're using and update the question with the code of the class that is calling the method CONN. – Ricardo A. Aug 16 '16 at 18:05

nullpointer when using shared prefference in no activity class

3 Answers3