Add value to array in Android

Question

I have class named as login (without encapsulate fields, I just want to make it simple)

public class login
{
    String username;
    String password;

    public login(String username, String password)
    {
        this.username = username;
        this.password = password;
    }
}

DisplayList.java

public class DisplayList extends ListActivity
{
    login[] values;

    protected void onCreate(Bundle savedInstanceState)
    {
        String username, password;
        int count = 0;
        while (count < somelength)
        {
            username = somestring;
            password = somestring;

            values[count] = new login(username, password);

            //if I Toast it
            //Toast.makeText(this, username + " . " + password, Toast.LENGTH_SHORT).show();

            count++;
        }

        login_adapter = new login_adapter(this, values);
        setListAdapter(login_adapter);
    }
}

I want to pass values (login[]values) to login_adapter (class login_adapter extends ArrayAdapter)

but I always come with NullPointerException on "values[count] = new login(username, password);"

if I Toast it "Toast.makeText(this, username + " . " + password, Toast.LENGTH_SHORT).show();" the Toast come with all values.

values = new login[4]; array initialization

Pavneet_Singh
– Pavneet_Singh

2017-01-17 15:02:57 +00:00
Commented Jan 17, 2017 at 15:02 — Pavneet_Singh
– Pavneet_Singh, Commented Jan 17, 2017 at 15:02

Pavneet_Singh · Accepted Answer · 2017-01-17 15:14:40Z

Use somelength to initialize your array ,because you are traversing in loop equal to the size of somelength and creating an object of login every time so

public class DisplayList extends ListActivity
{
    login[] values;

    protected void onCreate(Bundle savedInstanceState)
    {
        String username, password;
        int count = 0;

        values = new longin[somelength];
        // ^^^^   initialize your array 

        while (count < somelength)
        {
            username = somestring;
            password = somestring;
            values[count] = new login(username, password);
            count++;
        }
        login_adapter = new login_adapter(this, values);
        // make sure the login_adapter class name and object name is different            
        setListAdapter(login_adapter);
    }
}

For convention you can rename classes to login => Login ,login_adapter=> LoginAdapter

firegloves · Accepted Answer · 2017-01-17 15:05:55Z

0

You are not initializing your array. You need something like this at start of onCreate:

values = new login[2];

Note that for convention class names must start with uppercase carachter.

I suggest you to use ArrayList so you don't need to know array length at creation time

answered Jan 17, 2017 at 15:05

firegloves

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