iOS---实现在屏幕上实时绘图的简单效果---CAShaperLayer和UIBezierPath的简单运用

@property(nonatomic,strong)UIBezierPath * beizer;
@property(nonatomic,assign)CGPoint startPoint;
@property(nonatomic,assign)CGPoint movePoint;
@property(nonatomic,strong)CAShapeLayer * shapelayer;

- (void)viewDidLoad {
[super viewDidLoad];
UIPanGestureRecognizer * pan = [[UIPanGestureRecognizer alloc]initWithTarget:self action:@selector(panTouch:)];
[self.view addGestureRecognizer:pan];
self.beizer = [UIBezierPath bezierPath];
[self initCAShaper];

}
-(void)initCAShaper
{
self.shapelayer = [CAShapeLayer new];
self.shapelayer.frame = CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height);
self.shapelayer.fillColor = nil;
self.shapelayer.lineCap = kCALineCapRound;
self.shapelayer.strokeColor = [UIColor cyanColor].CGColor;
self.shapelayer.lineWidth =2;
[self.view.layer addSublayer:self.shapelayer];

}

-(void)panTouch:(UIPanGestureRecognizer *)pan
{
_startPoint = [pan locationInView:self.view];
if(pan.state == UIGestureRecognizerStateBegan)
{
[self.beizer moveToPoint:_startPoint];
}
if(pan.state == UIGestureRecognizerStateChanged)
{
_movePoint = [pan locationInView:self.view];
[_beizer addLineToPoint:_movePoint];
self.shapelayer.path = _beizer.CGPath;
}
}