implementing an EditText with line number on the left. What is new is: - get/set line number margin gap - set line number visible - set line number color Everything is done in the overridden onDraw() method.

LineNumberedEditText

import android.widget.*;
import android.util.*;
import android.content.*;
import android.graphics.*;

/**
* the simple implementation of an EditText where each line is numbered on the left
*/
public class LineNumberedEditText extends EditText {

/** whether to set the lines visible or not	*/
private boolean lineNumberVisible = false;

	private Rect _rect;
	private Paint lpaint;

/** the gap between the line number and the left margin of the text */
	private int lineNumberMarginGap = 2;

/**
*the difference between line text size and the normal text size.
* line text size is preferabl smaller than the normal text size
*/
	protected int LINE_NUMBER_TEXTSIZE_GAP = 2;

	public LineNumberedEditText (Context context, AttributeSet attrs) {
		super(context, attrs);
		_rect = new Rect();
		lpaint = new Paint();
		lpaint.setAntiAlias(true);
		lpaint.setStyle(Paint.Style.FILL);
		lpaint.setColor(Color.BLACK);
		lpaint.setTextSize(getTextSize() - LINE_NUMBER_TEXTSIZE_GAP);
	}

	public void setLineNumberMarginGap(int lineNumberMarginGap) {
		this.lineNumberMarginGap = lineNumberMarginGap;
	}

	public int getLineNumberMarginGap() {
		return lineNumberMarginGap;
	}

	public void setLineNumberVisible(boolean lineNumberVisible) {
		this.lineNumberVisible = lineNumberVisible;
	}

	public boolean isLineNumberVisible() {
		return lineNumberVisible;
	}

	public void setLineNumberTextColor(int textColor) {
		lpaint.setColor(textColor);
	}

	public int getLineNumberTextColor() {
		return	lpaint.getColor();
	}

	@Override
	protected void onDraw(Canvas canvas) {
		// TODO: Implement this method
		if (lineNumberVisible) {

//set the size in case it changed after the last update
lpaint.setTextSize(getTextSize() - LINE_NUMBER_TEXTSIZE_GAP);
		
	int baseLine = getBaseline();
			String t = "";
			for (int i = 0; i < getLineCount(); i++) {
				t = "" + (i + 1);
				canvas.drawText(t, _rect.left, baseLine, lpaint);
				baseLine += getLineHeight();
			}
			
// set padding again, adjusting only the left padding
			setPadding((int)lpaint.measureText(t) + lineNumberMarginGap, getPaddingTop(),
			getPaddingRight(), getPaddingBottom());
		}
		super.onDraw(canvas);
	}

}