我想做的是让用户触摸屏幕,当在该位置检测到触摸时,圆圈的大小将不断增大(并保持增长),直到用户松开为止。
我知道如何检测触摸,但问题是我试图绘制并随着其变大而重新绘制圆圈。
做这个的最好方式是什么?
最佳答案
我将结合使用UILongPressGestureRecognizer
,NSTimer
和UIBezierPath
来实现此目的。
首先,设置viewDidLoad
以添加并配置CAShapeLayer,以容纳要绘制的圆。以下代码最初将在屏幕上绘制一个半径为50点的圆,并向主视图添加长按手势。当然,触摸检测可以按照您想要的任何方式完成。哦,您需要为此导入Quartz。
- (void)viewDidLoad
{
[super viewDidLoad];
circleRadius = 50.0f;
circle = [CAShapeLayer layer];
[circle setAnchorPoint:CGPointMake(0.5f, 0.5f)];
[circle setFillColor:[UIColor clearColor].CGColor];
[circle setStrokeColor:[UIColor colorWithWhite:0.9f alpha:0.7f].CGColor];
[circle setLineWidth:5.0f];
[self.view.layer addSublayer:circle];
[self drawCircleWithRadius:circleRadius];
UILongPressGestureRecognizer *longPress = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector(longPressDetected:)];
[longPress setMinimumPressDuration:0.1];
[longPress setAllowableMovement:15.0f];
[self.view addGestureRecognizer:longPress];
}
然后,当识别到长按手势时,检查其状态。如果状态开始,则启动一个重复计时器以调用动画功能。手势结束后,请无效。
- (void)longPressDetected:(UILongPressGestureRecognizer *)sender {
if (sender.state == UIGestureRecognizerStateBegan) {
timer = [NSTimer scheduledTimerWithTimeInterval:0.1 target:self selector:@selector(animateImageView) userInfo:nil repeats:YES];
}else if (sender.state == UIGestureRecognizerStateEnded) {
[timer invalidate];
}
}
- (void)animateImageView {
circleRadius += 10.0f;
[self drawCircleWithRadius:circleRadius];
}
最后,下面的此函数将使用CABasicAnimation将形状图层的path属性动画化为上面指示的值(每次+10)。确保此动画持续时间不大于计时器重复间隔!
- (void)drawCircleWithRadius:(CGFloat)radius {
CABasicAnimation *pathAnimation = [CABasicAnimation animationWithKeyPath:@"path"];
[pathAnimation setFromValue:(id)circle.path];
[pathAnimation setToValue:(id)[UIBezierPath bezierPathWithRoundedRect:CGRectMake(0, 0, 2.0f * radius, 2.0f * radius) cornerRadius:radius].CGPath];
[pathAnimation setDuration:0.1];
[pathAnimation setRepeatCount:1.0f];
[pathAnimation setTimingFunction:[CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear]];
circle.path = [UIBezierPath bezierPathWithRoundedRect:CGRectMake(0, 0, 2.0*radius, 2.0*radius) cornerRadius:radius].CGPath;
circle.position = CGPointMake(CGRectGetMidX(self.view.frame)-radius, CGRectGetMidY(self.view.frame)-radius);
[circle addAnimation:pathAnimation forKey:@"changePathAnimation"];
}
希望这可以帮助!
关于iphone - 在iPhone中动态重绘调整大小的圆圈,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/15249675/