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

首先，声明几个属性

@property(nonatomic,strong)UIBezierPath * beizer;

@property(nonatomic,assign)CGPoint startPoint;

@property(nonatomic,assign)CGPoint movePoint;

@property(nonatomic,strong)CAShapeLayer * shapelayer;

然后注册屏幕上的拖拽事件，并初始化贝塞尔曲线和CAShapeLayer

- (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(, , 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 =;

    [self.view.layer addSublayer:self.shapelayer];

}

紧接着处理拖拽事件

-(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;

    }

}

大功告成。如图