Question

here i tried to take name and password from database if the user have already an account, or sign up him by enter his data.

This is the first activity which has force close by clicking on first button to log into the data base

public class SelesMeter2Activity extends Activity implements OnClickListener {
    EditText ed1;
    EditText ed2;
    Button b1;
    Button b2;
    SQLiteDatabase sql;
    Cursor c;
    Intent in;

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        ed1 = (EditText) findViewById(R.id.ed1);
        ed2 = (EditText) findViewById(R.id.ed2);
        b1 = (Button) findViewById(R.id.bt1);
        b2 = (Button) findViewById(R.id.bt2);
        b1.setOnClickListener(this);
        b2.setOnClickListener(this);
        sql = openOrCreateDatabase("db", 0, null);
        sql.execSQL("CREATE TABLE if not exists "
                + "Employee2 (password integer NOT NULL PRIMARY KEY,name text NOT NULL)");
    }

    @Override
    public void onClick(View arg0) {
        // log in
        if (arg0.getId() == R.id.bt1) {
            int p = 0;
            String name = ed1.getText().toString();
            String sp = ed2.getText().toString();
            try {
                // Attempt to parse the number as an integer
                p = Integer.parseInt(sp);
            } catch (NumberFormatException nfe) {
                // parseInt failed, so tell the user it's not a number
                Toast.makeText(this,
                        "Sorry, " + sp + " is not a number. Please try again.",
                        Toast.LENGTH_LONG).show();
            }
            if (c.getCount() != 0) {
                c = sql.rawQuery("select * from Employee", null);
                while (c.moveToNext()) {
                    if (name.equals("c.getString(1)") && p == c.getInt(0)) {
                        in = new Intent(this, secondview.class);
                        startActivity(in);
                        break;
                    }
                }
            }

            else {
                Toast.makeText(this,
                        "please sign up first or enter " + "correct data", 2000)
                        .show();
            }

        } else if (arg0.getId() == R.id.bt2) {
            // sign up
            Intent in2 = new Intent(this, signup.class);

            startActivity(in2);

        }
    }
}

the second class that enter the new user which is not working as expected,
the toast does not work :

public class signup extends Activity implements OnClickListener {
    EditText e1;
    EditText e2;
    SQLiteDatabase sql;
    Button b;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        setContentView(R.layout.singupx);
        Intent in = getIntent();
        e1 = (EditText) findViewById(R.id.ed1s);
        e2 = (EditText) findViewById(R.id.ed2s);
        b = (Button) findViewById(R.id.bt1s);
        b.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        String n = e1.getText().toString();
        String sp = e2.getText().toString();
        try {
            // Attempt to parse the number as an integer
            int p = Integer.parseInt(sp);
            // This insertion will *only* execute if the parseInt was successful
            // sql.execSQL("insert into Employee2(password,name)values('"+n+"',"+p+")");
            ContentValues values = new ContentValues();
            values.put("password", p);
            values.put("name", n);
            sql.insert("Employee2", null, values);
            Toast.makeText(this, "Data inserted", Toast.LENGTH_LONG).show();
            Intent in2 = new Intent(this, secondview.class);
            startActivity(in2);
        } catch (NumberFormatException nfe) {
            // parseInt failed, so tell the user it's not a number
            Toast.makeText(this,
                    "Sorry, " + sp + " is not a number. Please try again.",
                    Toast.LENGTH_LONG).show();
        }
    }
}

Answer 1

In the SelesMeter2Activity you’ll have a NullPointerException at the line:

if (c.getCount() != 0) {

as you don’t initialize the Cursor before that line. Move the query before the above line:

c = sql.rawQuery("select * from Employee", null);
if (c.getCount() != 0) {
     // ...

You should post the exception you get from the logcat.

Also regarding your signup activity please don’t instantiate the first activity to access fields from it. Open the database again in the second activity and insert the values.