frame_ref = new Frame("Login");
        mainPanel_ref = new Panel();
        buttonPanel_ref = new Panel();
        grid_ref = new GridLayout(4,2);
        frame_ref.setSize(300,120);
        frame_ref.setVisible(true);

        email_ref = new TextField();
        password_ref = new JPasswordField();

        mainPanel_ref.setLayout(grid_ref);
        mainPanel_ref.add(new Label("E-Mail"));
        mainPanel_ref.add(email_ref);
        mainPanel_ref.add(new Label("Passwort"));
        mainPanel_ref.add(password_ref);

        mainPanel_ref.add(submitLogin_ref);
        mainPanel_ref.add(fehlerMeldung_ref);

        frame_ref.add(mainPanel_ref);

我在上面用Java设置了一个视图.窗口完全为空,但在拖放其大小后,将显示所有元素.有人知道如何解决这个问题吗？