How to programmatically hide Imageview

I have a linearlayout with three icons as below

 <ImageView
            android:id="@+id/cities"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content          
            android:src="@drawable/city" />
    &lt;ImageView
        android:id="@+id/red"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"           
        android:src="@drawable/red"
        android:visibility="gone" 
        /&gt;
    &lt;ImageView
        android:id="@+id/deal"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"       
        android:src="@drawable/deal" /&gt;

initially the middle icon is hidden (android:visibility=“gone”) I have a login screen…when the login i success I want the icon to be visible …tried as below…but itz not working

public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);
setContentView(R.layout.fyelogin);                    
etPassword = (EditText)findViewById(R.id.password);
btnLogin = (Button)findViewById(R.id.login_button);
btnCancel = (Button)findViewById(R.id.cancel_button);
lblResult = (TextView)findViewById(R.id.result);

final ImageView details = (ImageView)findViewById(R.id.red); 

btnLogin.setOnClickListener(new OnClickListener() {
    public void onClick(View v) {

        String password = etPassword.getText().toString();

        if(password.equals("guest")){
            lblResult.setText("password successful.");

giving error @ this line  -----&gt;  details.setVisibility(View.VISIBLE);

        } else {
            lblResult.setText("password doesn't match.");
        }

        finish();
    }
});

#android