def write(self, text="", xy=(0,0), align="left", font=None, fontName=None, fontSize = 10, fill = 1, spacing = 0, screenCenter = False):
        """!
        \~english 
        Print one line text or multi-line text on the screen
        @param text: Text to be drawn. eg. "Hello World!" or "Hello/nWorld!"
        @param xy: Top left corner of the text. defaule: (0,0)
        @param align: "left", "center" or "right". defaule: "left"
        @param fontName: Name of font or font instance. defaule: None (use default font) 
        @param fontSize: Font size. default: 10
        @param fill: Color to use for the text. default: 1 (white)
        @param spacing: The number of pixels between lines. default: 0
        @param screenCenter： Keep the text center of screen. default: False
        
        @note
        How to use screenCenter?
        1. align="left"; screenCenter=False
        <pre>
        +---------------------------------+
        |  Simple text line1              |
        |  Simple line2                   |
        |  Simple                         |
        |                                 |
        +---------------------------------+
        </pre>
        
        2. align="left"; screenCenter=True
        <pre>
        +---------------------------------+
        |        Simple text line1        |
        |        Simple line2             |
        |        Simple                   |
        |                                 |
        +---------------------------------+
        </pre>

        \~chinese
        在屏幕上打印一行文字或多行文字        
        @param text: 要输出的文字，可以单行也可以多行。例如： "Hello World!"  或 "Hello/nWorld!"
        @param xy: 文字输出的坐标点。默认： (0,0)
        @param align: 多行文字对齐方式，可选： "left", "center" 或 "right". 默认： "left"
        @param fontName: 字体名或字体对象实例。默认：None（使用系统默认的字体） 
        @param fontSize: 字体大小。默认：10
        @param fill: 文字颜色。默认： 1 （白色）
        @param spacing: 行间距。默认：0
        @param screenCenter： 让文本居中屏幕。
        
        @note
        screenCenter 效果示例：
        1. align="left"; screenCenter=False
        <pre>
        +---------------------------------+
        |  Simple text line1              |
        |  Simple line2                   |
        |  Simple                         |
        |                                 |
        +---------------------------------+
        </pre>
        
        2. align="left"; screenCenter=True
        <pre>
        +---------------------------------+
        |        Simple text line1        |
        |        Simple line2             |
        |        Simple                   |
        |                                 |
        +---------------------------------+
        </pre>
        """
        tx = xy[0]
        
        try:
            dwFont = font if font != None else DEF_SCR_FRONT if fontName==None else ImageFont.truetype(fontName, fontSize)
        except:
            dwFont = DEF_SCR_FRONT

        try:
            if screenCenter == True:
                (fw, fh) = self.Canvas.multiline_textsize( text, font )
                tx = xy[0] + (self._display_size[0]-fw)/2
            self.Canvas.multiline_text( (tx, xy[1]) , text, font = dwFont, align=align, fill=fill, spacing=spacing)
        except:
            print("ERROR: canvas write error")