Question

我使用核心动画（CAKeyframeAnimation）使用给定路径移动视图，同时显示路径（虚线）。在沿着给定路径制作视图的动画时，我希望它面向它将要去的方向。换句话说，我希望视图在移动时逐渐旋转。

经过一些研究后我发现使用关键时间和值可以使用CAKeyFrameAnimation进行，但没有成功。我不知道如何实现它。

由于我仍然是IOS编程的新手，我不知道是否还有另一种（更好的？）方式来做这种动画。

以下是我使用的代码：

- (CGMutablePathRef) getPathFromPoints:(NSMutableArray*)points {
        CGMutablePathRef path = CGPathCreateMutable();
        CGPoint p = [points[0] CGPointValue];
        CGPathMoveToPoint(path, NULL, p.x, p.y);
        for (int i = 1; i < points.count; ++i) {
            p = [points[i] CGPointValue];
            CGPathAddLineToPoint(path, NULL, p.x, p.y);
        }
        return path;
    }

    - (void)animateView:(UIView*)view
             withPoints:(NSMutableArray*)points
           withFillMode:(NSString*)fillMode
           withDuration:(int)duration
        withRepeatCount:(int)repeat
              withSpeed:(int)speed
             withDashed:(BOOL)dashed{

        CGMutablePathRef path = [self getPathFromPoints:points];

        if (dashed) {
            CAShapeLayer* pathLayer = [CAShapeLayer layer];
            pathLayer.frame = view.superview.layer.bounds;
            pathLayer.bounds = view.superview.layer.bounds;
            pathLayer.geometryFlipped = NO;
            pathLayer.path = path;
            pathLayer.strokeColor = [[UIColor blackColor] CGColor];
            pathLayer.fillColor = nil;
            pathLayer.lineWidth = 10.0f;
            pathLayer.lineJoin = kCALineJoinBevel;
            [pathLayer setLineDashPattern:[[NSArray alloc] initWithObjects:
                                           [NSNumber numberWithInt:15],
                                           [NSNumber numberWithInt:15],
                                           nil]];
            [view.superview.layer addSublayer:pathLayer];

            CABasicAnimation *dottedAnimation = [CABasicAnimation     animationWithKeyPath:@"strokeEnd"];
            dottedAnimation.duration = duration;
            dottedAnimation.fromValue = [NSNumber numberWithFloat:0.0f];
            dottedAnimation.toValue = [NSNumber numberWithFloat:1.0f];
            [pathLayer addAnimation:dottedAnimation forKey:@"strokeEnd"];

            [view.superview bringSubviewToFront:view];
        }

        CAKeyframeAnimation* pathAnimation = [CAKeyframeAnimation animationWithKeyPath:@"position"];
        pathAnimation.calculationMode = kCAAnimationPaced;
        pathAnimation.fillMode = fillMode;
        pathAnimation.duration =  duration;
        pathAnimation.repeatCount = repeat;
        pathAnimation.speed = speed;
        pathAnimation.path = path;
        [view.layer addAnimation:pathAnimation forKey:_myAnimationKey];
        CGPoint p = [[points lastObject] CGPointValue];
        view.layer.position = CGPointMake(p.x, p.y);
    }

提前感谢您的帮助，

Answer 1

查看CAKeyframeAnimation的rotationMode属性。这应该完全符合你的希望。

将此行添加到-animateView：方法中，其中设置了* pathAnimation CAKeyframeAnimation实例的属性：

pathAnimation.rotationMode = kCAAnimationRotateAuto;

还有另一个设置值kCAAnimationRotateAutoReverse，它允许动画对象保持相对于路径切线的反平行方向。

指向Apple文档的链接：CAKeyframeAnimation

如何使用核心动画旋转已经移动的视图？

1 个答案: