Wordpress plugin development OOP style

Question

I am building my first oop based plugin.This main problem is that it is not showing settings field(font error input).So far my approach..

$plugin_settings = new WordPress_Plugin_Template_Settings( __FILE__ );

The class is

class WordPress_Plugin_Template_Settings {
    private $dir;
    private $file;
    private $assets_dir;
    private $assets_url;

    public function __construct( $file ) {
        $this->file = $file;
        $this->dir = dirname( $this->file );
        $this->assets_dir = trailingslashit( $this->dir ) . 'assets';
        $this->assets_url = esc_url( trailingslashit( plugins_url( '/assets/', $this->file ) ) );
        register_activation_hook( __FILE__,array( $this, 'ma_defaults_options' ) );
        add_action( 'admin_init', array( $this, 'ma_admin_options_init' ) );
        add_action( 'admin_menu', array( $this, 'add_menu_item' ) );
    }

    function ma_defaults_options() {
        $default_options = get_option( 'ma_admin_styler' );
        if( ( !is_array( $default_options ) ) ) {
            $default = array( 
                "error_font_color"  => "#ffff",
            );
            update_option( 'ma_admin_styler', $default );
        }
    }

    public function add_menu_item() {
        add_options_page( 'Plugin Settings', 'Plugin Settings', 'edit_theme_options',  'ma_admin_styler',  array( $this, 'settings_page' ) );
    }

    public function ma_admin_options_init() {
        register_setting( 'ma_admin_styler', 'ma_admin_styler', array( $this,'ma_admin_styler_validate' ) );
        add_settings_section( 'main_section', '', array( $this,'section_text_default' ), __FILE__ );
        add_settings_field( 'error_font_color', 'Error Font Color', array( $this,'ma_error_font_color' ), __FILE__, 'main_section' );
    }

    function section_text_default() {
    }

    function ma_error_font_color() {
        $options = get_option( 'ma_admin_styler' );
        echo "<input name='ma_admin_styler[error_font_color]' class='wp-color-picker-field' data-default-color='#ffffff' id='color'value='{$options['error_font_color']}' />";
    }

    function settings_page() {
        echo '<div class="wrap">
                <div class="icon32" id="plugin_settings-icon"><br/></div>
                <h2>Plugin Settings</h2>
                <form method="post" action="options.php" enctype="multipart/form-data">';

        settings_fields( 'ma_admin_styler' );
        do_settings_sections( 'ma_admin_styler' );

        echo '<p class="submit">
                        <input name="Submit" type="submit" class="button-primary" value="' . esc_attr( __( 'Save Settings', 'plugin_textdomain' ) ) . '" />
                    </p>
                </form>
            </div>';
    }
}

I think I have error in add_settings_field('error_font_color', 'Error Font Color', array( $this,'ma_error_font_color'), __FILE__, 'main_section');

Answer 1

Change ma_admin_options_init() to:

public function ma_admin_options_init(){
  register_setting('ma_admin_styler', 'ma_admin_styler', array(  $this,'ma_admin_styler_validate'));
  add_settings_section('main_section', '', array( $this,'section_text_default'), 'ma_admin_styler');
  add_settings_field('error_font_color', 'Error Font Color', array(   $this,'ma_error_font_color'), 'ma_admin_styler', 'main_section');
}

The fourth parameter of add_settings_section() and add_settings_field() is $page and that needs to match the page ID set in add_options_page().