SimpleDrawingView.java

package com.example.butterknifedemo;

import java.util.ArrayList;
import java.util.List;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Point;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;

public class SimpleDrawingView extends View {

	// setup initial color
	  private final int paintColor = Color.BLACK;
	  
	  // defines paint and canvas
	  private Paint drawPaint;
	  
	  // Store circles to draw each time the user touches down
	  private List<Point> circlePoints;

	public SimpleDrawingView(Context context, AttributeSet attrs) {
		super(context, attrs);
		setFocusable(true);		// Allows the view to receive touch events
		setFocusableInTouchMode(true);
		setupPaint();
		circlePoints = new ArrayList<Point>();
	}

	// Setup paint with color and stroke styles
	private void setupPaint() {
		drawPaint = new Paint();
		drawPaint.setColor(paintColor);
		drawPaint.setAntiAlias(true);
		drawPaint.setStrokeWidth(5);
		//drawPaint.setStyle(Paint.Style.STROKE);
		drawPaint.setStyle(Paint.Style.FILL); // change to fill
		drawPaint.setStrokeJoin(Paint.Join.ROUND);
		drawPaint.setStrokeCap(Paint.Cap.ROUND);
	}

	// Draw each circle onto the view
	@Override
	protected void onDraw(Canvas canvas) {
		for (Point p : circlePoints) {
			canvas.drawCircle(p.x, p.y, 5, drawPaint);
		}
	}

	// Append new circle each time user presses on screen
	@Override
	public boolean onTouchEvent(MotionEvent event) {
		float touchX = event.getX();
		float touchY = event.getY();
		circlePoints.add(new Point(Math.round(touchX), Math.round(touchY)));
		// indicate view should be redrawn
		postInvalidate();
		return true;
	}
}