nullpointerexception on launcher? android

i'm trying to create a really simple login page, but I get an error when i try to launch the app. I don't get it at all, since that I've basically made it like I had the other launcher. And i have put the intent filter on this new activity. any help would be appreciated, since I have to Present it tomorrow at my exam. Here's the code. the thing about insert, is just for now, and I will change that later.

public class LoginActivity extends Activity implements OnClickListener {

EditText loginUsername,loginPassword;
Button loginButton;
SQLiteDatabase db;

public void onCreate(Bundle savedInstanceState)
{ 

    super.onCreate(savedInstanceState);
    setContentView(R.layout.login);
    loginUsername=(EditText)findViewById(R.id.loginUsername);
    loginPassword=(EditText)findViewById(R.id.loginPassword);
    loginButton.setOnClickListener(this);
    db=openOrCreateDatabase("StudentDB", Context.MODE_PRIVATE, null);
    db.execSQL("CREATE TABLE IF NOT EXISTS studentTest5(rollno VARCHAR,name VARCHAR,lastname VARCHAR,password VARCHAR,marks VARCHAR, phone VARCHAR, email VARCHAR);");
    db.execSQL("INSERT INTO studentTest5 VALUES('1','Lars','Hansen','1234','7','60158096','[email protected]');");
}


@Override
public void onClick(View view) {
    // TODO Auto-generated method stub
    if(view==loginButton)
    {
        if(loginUsername.getText().toString().trim().length()==0||
           loginPassword.getText().toString().trim().length()==0)
        {
            showMessage("Error", "Please enter all values");
            return;
        }
        Cursor c=db.rawQuery("SELECT * FROM studentTest5 WHERE name='"+loginUsername.getText()+"'", null);
        if(c.moveToFirst())
        {
            if(c.getString(3)==loginPassword.getText().toString())
            {
                showMessage("sucess", "user exists");
                //loginPassword.setText(c.getString(3));
                } else {
                    showMessage("Error", "incorrect password");
                }


        }
        else
        {
            showMessage("Error", "Invalid Rollno");
            clearText();
        }

    }

}
 public void showMessage(String title,String message)
    {
        Builder builder=new Builder(this);
        builder.setCancelable(true);
        builder.setTitle(title);
        builder.setMessage(message);
        builder.show();
    }
    public void clearText()
    {
        loginUsername.setText("");
        loginPassword.setText("");

    }

}

here is the xml

<TextView
    android:id="@+id/loginWelcome"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentTop="true"
    android:layout_centerHorizontal="true"
    android:layout_marginTop="65dp"
    android:text="Welcome!"
    android:textAppearance="?android:attr/textAppearanceLarge" />

<EditText
    android:id="@+id/loginUsername"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@+id/loginWelcome"
    android:layout_centerHorizontal="true"
    android:layout_marginTop="20dp"
    android:ems="10"
    android:hint="Login"
    android:inputType="textPersonName" />

<EditText
    android:id="@+id/loginPassword"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignLeft="@+id/loginUsername"
    android:layout_alignRight="@+id/loginUsername"
    android:layout_below="@+id/loginUsername"
    android:layout_marginTop="14dp"
    android:ems="10"
    android:hint="Password"
    android:inputType="textPassword" />

<Button
    android:id="@+id/loginButton"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignLeft="@+id/loginPassword"
    android:layout_alignRight="@+id/loginPassword"
    android:layout_below="@+id/loginPassword"
    android:layout_marginTop="30dp"
    android:text="Login" />

</RelativeLayout>

and here's the error message

   FATAL EXCEPTION: main
   Process: com.technotalkative.viewstubdemo, PID:     10998
   java.lang.RuntimeException: Unable to start activity      ComponentInfo{com.technotalkative.viewstubdemo/com.technotalkative.viewstubdemo.LoginActivity}:      java.lang.NullPointerException
    at  android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2184)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2233)
    at android.app.ActivityThread.access$800(ActivityThread.java:135)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
    at android.os.Handler.dispatchMessage(Handler.java:102)
    at android.os.Looper.loop(Looper.java:136)
    at android.app.ActivityThread.main(ActivityThread.java:5001)
    at java.lang.reflect.Method.invokeNative(Native Method)
    at java.lang.reflect.Method.invoke(Method.java:515)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
    at dalvik.system.NativeStart.main(Native Method)
    Caused by: java.lang.NullPointerException
    at com.technotalkative.viewstubdemo.LoginActivity.onCreate(LoginActivity.java:27)
    at android.app.Activity.performCreate(Activity.java:5231)
    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2148)
    ... 11 more