The drawString() method that is used to write text on the canvas dose not know how to wrap the text, hence,  when using it and writing a long text, only one line will appear and the text will be cut.

In order to have the text written correctly, there is a need to implement a text wrap.

The below function writes the given ‘txt’ on the canvas’s Graphics ‘g’, starting from ‘x’ and ‘y’ coordinates, using the given ‘font’. the area in which the text should be written is ‘width’ and the text is written by the ‘alignment’ . using the alignment you can write text from left to right or from right to left

The function returns the next y coordinate on the canvas, which is the next location for a text to be written. this is good for cases that you want to continue writing on the canvas but with a different font or color.

public int write(Graphics g, String txt, int x, int y,
                         int width, Font font,
                         int alignment ){
    m_font = font;
    m_txt = txt;
    m_length = txt.length();
    m_width = width;
    //reseting
    m_position =0;
    m_start = 0;

    int fontHight = m_font.getHeight() + 1;
    String s;
    g.setFont(m_font);
    while(hasMoreLines()){
    s = nextLine().trim();
    g.drawString(s, x, y, Graphics.TOP|alignment );
    y += fontHight;
    }
    return y;
}

below is the implementation  for the  "helper" functions

private boolean hasMoreLines(){
    return (m_position<(m_length-1));
}

private String nextLine(){
     int maxLength = m_txt.length();
     int next = next();
     if(m_start>=maxLength || next>maxLength)
          return null;
     String s =m_txt.substring(m_start, next);
     m_start = next;
     if((m_txt.length()-1>m_start )&& ((m_txt.charAt(m_start)=='\n') ||
        (m_txt.charAt(m_start)==' '))){
          m_position++;
          m_start++;
     }
     return s;
}

private int next(){
     int i=getNextWord(m_position);
     int lastBreak = -1;
     String line;
     line= m_txt.substring(m_position, i);
     int lineWidth = m_font.stringWidth(line);
     while (i<m_length && lineWidth<= m_width){
         if(m_txt.charAt(i)==' ' )
            lastBreak = i;
         else if(m_txt.charAt(i)== '\n'){
            lastBreak =i;
            break;
         }
         if(++i<m_length){
            i= getNextWord(i);
            line = m_txt.substring(m_position, i);
            lineWidth = m_font.stringWidth(line);
         }
     }
     if(i==m_length && lineWidth<= m_width)
        m_position = i;
     else if(lastBreak == m_position)
        m_position++;
     else if(lastBreak < m_position)
        m_position =i;
     else
        m_position = lastBreak;
     return m_position;
  }

private int getNextWord(int startIndex){
    int space = m_txt.indexOf(' ', startIndex);
    int newLine = m_txt.indexOf('\n', startIndex);
    if(space ==-1)
       space = m_length;
    if(newLine ==-1)
       newLine = m_length;
    if(space<newLine)
       return space;
    else
      return newLine;
}

Tags: Canvas, GUI, J2ME, right to left, Text wrapping

This entry was posted on Wednesday, February 27th, 2008 at 1:24 am and is filed under GUI, J2ME. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.