ios建立畫筆的例子(雙筆畫效果）

定義一個UIView：主要是在這個View裡面加一個UIImageView,畫圖都在這個UIImageView裡面進行

@property(nonatomic) CGPoint prePoint;  //手指在進入move事件之前的那個點@property(nonatomic) CGPoint oppsitePoint;  //手指在進入move事件之前的那個點@property(nonatomic, retain) UIImageView* drawImage;- (id)initWithFrame:(CGRect)frame{    self = [super initWithFrame:frame];    if (self) {        // Initialization code        self.drawImage = [[UIImageView alloc] initWithImage:nil];        self.drawImage.frame = self.frame;        [self addSubview:_drawImage];            }    return self;}

然後處理手指的事件

#pragma mark - deal touch-(void) touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event{    NSLog(@"touchesBegan");    //下面兩句知道手指在螢幕上的點的資訊    UITouch* touch = [touches anyObject];    CGPoint point = [touch locationInView:self];        if (touch) {        self.prePoint = point;        _oppsitePoint = point;        _oppsitePoint.x = 320.0f - point.x;    }}-(void) touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event{     NSLog(@"touchesMoved");    UITouch* touch = [touches anyObject];    if (touch) {        CGPoint point = [touch locationInView:self];        UIGraphicsBeginImageContext(self.frame.size);        [_drawImage.image drawInRect:CGRectMake(0, 0, _drawImage.frame.size.width, _drawImage.frame                                                .size.height)];        CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);        CGContextSetLineWidth(UIGraphicsGetCurrentContext(), 2.0f);        CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(),0.314, 0.486, 0.859, 1.0);        CGContextBeginPath(UIGraphicsGetCurrentContext());        CGContextMoveToPoint(UIGraphicsGetCurrentContext(), _prePoint.x, _prePoint.y);         CGContextAddQuadCurveToPoint(UIGraphicsGetCurrentContext(), _prePoint.x, _prePoint.y, point.x, point.y);                CGContextMoveToPoint(UIGraphicsGetCurrentContext(), _oppsitePoint.x, _oppsitePoint.y);        CGContextAddQuadCurveToPoint(UIGraphicsGetCurrentContext(), _oppsitePoint.x, _oppsitePoint.y, 320.0f - point.x, point.y);               // CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), point.x, point.y);        CGContextStrokePath(UIGraphicsGetCurrentContext());        _drawImage.image = UIGraphicsGetImageFromCurrentImageContext();        UIGraphicsEndImageContext();                _prePoint = point;        _oppsitePoint = point;        _oppsitePoint.x = 320.0f - point.x;                    }    }-(void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event{    NSLog(@"touchesEnded");        //這段的作用是如果在螢幕上點擊可以畫出點    UIGraphicsBeginImageContext(self.frame.size);    [_drawImage.image drawInRect:CGRectMake(0, 0, _drawImage.frame.size.width, _drawImage.frame                                            .size.height)];    CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);    CGContextSetLineWidth(UIGraphicsGetCurrentContext(), 3.0f);    CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(),0.314, 0.486, 0.859, 1.0);    CGContextBeginPath(UIGraphicsGetCurrentContext());    CGContextMoveToPoint(UIGraphicsGetCurrentContext(), _prePoint.x, _prePoint.y);    CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), _prePoint.x, _prePoint.y);    CGContextStrokePath(UIGraphicsGetCurrentContext());    _drawImage.image = UIGraphicsGetImageFromCurrentImageContext();    UIGraphicsEndImageContext();    self.isTouch = NO;}

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