iOS实现贝塞尔曲线动画

本文实例为大家分享了iOS实现贝塞尔曲线动画的具体代码，供大家参考，具体内容如下

效果如图：

仿美人相机，手势滑动隐藏顶部view。为了方便讲解，将屏幕分为几个区域，如图：

在拖动过程中：

1、拖动距离小于minMoveDistance，贝赛尔曲线发生形变
2、拖动大于minMoveDistance，整个view开始下移

在松开手时：

1、拖动距离小于minMoveDistance，未发生位移，贝塞尔曲线恢复形变
2、拖动大于minMoveDistance，小于minDisappearDistance，贝塞尔曲线恢复形变、位移回到初始位置。
3、拖动大于minDisappearDistance，向下移动隐藏view

一、根据y轴位移量确定贝塞尔路径

在拖动时曲线形变、松手时曲线恢复形变的时候都需要改变贝塞尔曲线，实际上是改变二阶贝塞尔曲线的控制点，因此写一个方法，根据传入的y轴位移量得到新的贝塞尔路径：

- (CGPathRef)getPathWithMoveDistance:(CGFloat)distance{

    UIBezierPath *path = [UIBezierPath bezierPath];
    CGPoint startPoint = CGPointMake(0, 0);
    CGPoint controlPoint = CGPointMake(self.bounds.size.width*0.5, 60+distance);
    CGPoint endPoint = CGPointMake(self.bounds.size.width, 0);

    [path moveToPoint:startPoint];
    [path addQuadCurveToPoint:endPoint controlPoint:controlPoint];

    [path addLineToPoint:CGPointMake(self.bounds.size.width, self.bounds.size.height)];
    [path addLineToPoint:CGPointMake(0, self.bounds.size.height)];

    return path.CGPath;
}

二、初始化图形

初始化的时候，可以根据上一步的方法，传入位移量0，获取贝塞尔路径，并将获得的路径赋给CAShapeLayer：

- (id)initWithFrame:(CGRect)frame{
    if (self = [super initWithFrame:frame]) {
        self.originY = frame.origin.y;
        [self setUpLayer];
        [self addGesure];
    }
    return self;
}

- (void)setUpLayer{
    self.topLineLayer = [CAShapeLayer layer];
    self.topLineLayer.fillColor = ColorForTheme.CGColor;
    self.topLineLayer.strokeColor = ColorForTheme.CGColor;
    self.topLineLayer.path = [self getPathWithMoveDistance:0];
    [self.layer addSublayer:self.topLineLayer];
}

三、添加手势

添加UIPanGestureRecognizer拖动手势，并处理手势拖动和结束拖动的事件。

拖动时：

1、拖动距离小于minMoveDistance，只有贝赛尔曲线发生形变，调用步奏一中的方法。
2、拖动距离大于minMoveDistance，整个view开始下移

结束拖动时：

调用revertFormY:方法，传入当前在y轴上已经发生的位移量

- (void)addGesure{
    if (self.gesture == nil) {
        self.gesture = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(handlePan:)];
    }
    [self addGestureRecognizer:self.gesture];
}

- (void)handlePan:(UIPanGestureRecognizer *)gesture{
    CGFloat distanceX = [gesture translationInView:self].x;
    CGFloat distanceY = [gesture translationInView:self].y;

    if (ABS(distanceX) > ABS(distanceY)) {
        return;
    }
    //拖动过程
    if (gesture.state == UIGestureRecognizerStateChanged) {
        NSLog(@"%f",distanceY);

        //移动少于minMoveDistance，贝赛尔曲线形变
        if (distanceY > 0 && distanceY <= minMoveDistance) {
            self.topLineLayer.path = [self getPathWithMoveDistance:distanceY];
        }
        //移动大于minMoveDistance，整个view下移
        else if (distanceY > minMoveDistance) {
            self.frame = CGRectMake(0, self.originY+distanceY-minMoveDistance, self.bounds.size.width, self.bounds.size.height);
        }
    }
    //手势结束
    if (gesture.state == UIGestureRecognizerStateEnded || gesture.state == UIGestureRecognizerStateCancelled || gesture.state == UIGestureRecognizerStateFailed) {
        [self removeGestureRecognizer:self.gesture];
        [self revertFormY:distanceY];
    }
}

四、revertFormY：恢复形变方法

根据传入的y轴上的位移量，实现不同的效果：

1、y小于minMoveDistance，未发生位移，贝塞尔曲线恢复形变
2、y大于minMoveDistance，小于minDisappearDistance，贝塞尔曲线恢复形变、位移回到初始位置。
3、y大于minDisappearDistance，向下移动隐藏view

//手势结束后恢复或隐藏
-(void)revertFormY:(CGFloat)y{

    //y < 最小的隐藏位移距离，未发生位移，贝塞尔曲线恢复动画
    if (y < minDisappearDistance) {
        CAKeyframeAnimation *vibrate = [CAKeyframeAnimation animationWithKeyPath:@"path"];
        vibrate.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseIn];
        vibrate.values = @[
                           (id) [self getPathWithMoveDistance:y],
                           (id) [self getPathWithMoveDistance:-(y * 0.3)],
                           (id) [self getPathWithMoveDistance:(y * 0.2)],
                           (id) [self getPathWithMoveDistance:-(y * 0.15)],
                           (id) [self getPathWithMoveDistance:(y * 0.1)],
                           (id) [self getPathWithMoveDistance:-(y * 0.07)],
                           (id) [self getPathWithMoveDistance:(y * 0.05)],
                           (id) [self getPathWithMoveDistance:0.0]
                           ];
        vibrate.duration = 0.5;
        vibrate.removedOnCompletion = NO;
        vibrate.fillMode = kCAFillModeForwards;
        vibrate.delegate = self;
        [self.topLineLayer addAnimation:vibrate forKey:nil];
    }

    //y > 最小位移距离，发生了位移
    if(y > minMoveDistance){
        [UIView animateWithDuration:0.3 animations:^{
            CGFloat endY;
            //向上恢复view
            if (y < minDisappearDistance) {
                endY = self.originY;
            }
            //向下隐藏view
            else{
                endY = SCREEN_HEIGHT;
            }
            self.frame = CGRectMake(0, endY, SCREEN_WIDTH, self.frame.size.height);
        }];
    }
}

五、双击屏幕空白，消失的view从底部上移，恢复到初始位置

这个只是为了回到初始状态，根据实际需求实现。

//恢复到初始位置
- (void)comeBack{
    if (self.frame.origin.y <= self.originY) {
        return;
    }

    [UIView animateWithDuration:0.3 animations:^{
        self.frame = CGRectMake(0, self.originY, SCREEN_WIDTH, self.frame.size.height);
    } completion:^(BOOL finished) {
        [self revertFormY:10];
    }];
}

完整代码