iOS 判断用户触摸屏 画图

//
//  TouchMoveView.m
//  UITouch
//
//  Created by 公开课 on 13-4-21.
//  Copyright (c) 2013年 公开课. All rights reserved.
//

#import "TouchMoveView.h"
#import <CoreGraphics/CGColor.h>

@implementation TouchMoveView
{
    

}
- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        // Initialization code
    }
    return self;
}

/**/
// Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.
- (void)drawRect:(CGRect)rect
{
    // Drawing code
    drawImage = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"1.jpg"]];
    drawImage.frame = self.frame;
    [self addSubview:drawImage];
    mouseMoved = 0;
}
-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event{
    mouseSwiped = NO;
    UITouch *touch = [touches anyObject];
    
    if ([touch tapCount] == 2) {
        drawImage.image = nil;
        return;
    }
    lastPoint = [touch locationInView:self];
    lastPoint.y -= 20;
    
}
-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event{
    mouseSwiped = YES;
    UITouch *touch = [touches anyObject];
    CGPoint currentPoint = [touch locationInView:self];
    currentPoint.y -= 20; // only for 'kCGLineCapRound'
    UIGraphicsBeginImageContext(self.frame.size);
    //Albert Renshaw - Apps4Life
    [drawImage.image drawInRect:CGRectMake(0, 0, drawImage.frame.size.width, drawImage.frame.size.height)]; //originally self.frame.size.width, self.frame.size.height)];
    CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound); //kCGLineCapSquare, kCGLineCapButt, kCGLineCapRound
    CGContextSetLineWidth(UIGraphicsGetCurrentContext(), 20.0); // for size
    CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), 0.0, 0.0, 0.0, 1.0); //values for R, G, B, and Alpha
    CGContextBeginPath(UIGraphicsGetCurrentContext());
    CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
    CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), currentPoint.x, currentPoint.y);
    CGContextStrokePath(UIGraphicsGetCurrentContext());
    drawImage.image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    
    lastPoint = currentPoint;
    mouseMoved++;
    
    if (mouseMoved == 10) {
        mouseMoved = 0;
    }
    
}
-(void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event{
    UITouch *touch = [touches anyObject];
    if ([touch tapCount] == 2) {
        drawImage.image = nil;
        return;
    }
    if(!mouseSwiped) {
        
        UIGraphicsBeginImageContext(self.frame.size);
        [drawImage.image drawInRect:CGRectMake(0, 0, drawImage.frame.size.width, drawImage.frame.size.height)]; //originally self.frame.size.width, self.frame.size.height)];
        CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound); //kCGLineCapSquare, kCGLineCapButt, kCGLineCapRound
        CGContextSetLineWidth(UIGraphicsGetCurrentContext(), 20.0);
        CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), 0.0, 0.0, 0.0, 1.0);
        CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
        CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
        CGContextStrokePath(UIGraphicsGetCurrentContext());
        CGContextFlush(UIGraphicsGetCurrentContext());
        drawImage.image = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();
    }
}
- (void) clear{
    [drawImage setImage:[UIImage imageNamed:@"Writingview.png"]];
}
@end