Touch e Canvas - ANDROID

package com.example.projetoandroid;

  import android.content.Context;
  import android.graphics.Canvas;
  import android.graphics.Color;
  import android.graphics.Paint;
  import android.view.MotionEvent;
  import android.view.View;
  import android.view.View.OnTouchListener;

public class Tela1 extends View implements OnTouchListener 
{
	Paint paint;
	int x = 0;
	int y = 0;

	public Tela1(Context context) 
	{
		super(context);
		paint = new Paint();
	}
	
	public void onDraw(Canvas canvas)
	{
	   super.onDraw(canvas);
	   paint.setColor(Color.BLACK);
	  
	   canvas.drawPaint(paint);
	  
	    //Quadricular Tela
	  
	    paint.setColor(Color.rgb(220, 220, 220));
	  
	    for(int i = 0; i <= canvas.getHeight();i+=20)
	    {
		  canvas.drawLine(i, 0, i, canvas.getHeight(), paint); //vertical
		  canvas.drawLine(0, i,canvas.getWidth(),i, paint);    //horizontal
	    }
	  
	    paint.setColor(Color.GREEN);
	    canvas.drawCircle(x, y, 40, paint);	  
	  }

	  @Override
	  public boolean onTouch(View view, MotionEvent me) 
	  {
	    x = (int)me.getX();
	    y = (int)me.getY();
	  	  
	    return false;
	  }

  }