Question

所以，

我正在尝试做一个非常简单的光盘旋转（2d），根据用户的触摸，就像DJ或其他东西。它有效，但是有一个问题，经过一定的旋转后，它开始向后移动，这个数量是180度之后，或者当我记录角度时看到的，-3.14（pi）。

我想知道，我怎么能实现无限循环，我的意思是，用户可以保持旋转并旋转到任何一侧，只需滑动他的手指？还有第二个问题是，有没有办法加快轮换？

这是我现在的代码：

#import <UIKit/UIKit.h>

@interface Draggable : UIImageView {
    CGPoint firstLoc;
    UILabel * fred;
    double angle;
}

@property (assign) CGPoint firstLoc;
@property (retain) UILabel * fred;

@end


@implementation Draggable

@synthesize fred, firstLoc;

- (id)initWithFrame:(CGRect)frame {
    self = [super initWithFrame:frame];

    angle = 0;
    if (self) {
        // Initialization code
    }
    return self;
}
-(void)handleObject:(NSSet *)touches
          withEvent:(UIEvent *)event
             isLast:(BOOL)lst
{
    UITouch *touch =[[[event allTouches] allObjects] lastObject];
    CGPoint curLoc = [touch locationInView:self];

    float fromAngle = atan2( firstLoc.y-self.center.y,
                            firstLoc.x-self.center.x );
    float toAngle = atan2( curLoc.y-(self.center.y+10),
                          curLoc.x-(self.center.x+10));
    float newAngle = angle + (toAngle - fromAngle);

    NSLog(@"%f",newAngle);

    CGAffineTransform cgaRotate = CGAffineTransformMakeRotation(newAngle);

    self.transform = cgaRotate;

    if (lst)
        angle = newAngle;
}

-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    UITouch *touch =[[[event allTouches] allObjects] lastObject];
    firstLoc = [touch locationInView:self];
};


-(void) touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
    [self handleObject:touches withEvent:event isLast:NO];
};

-(void) touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
    [self handleObject:touches withEvent:event isLast:YES];
}

@end

在ViewController中：

UIImage *tmpImage = [UIImage imageNamed:@"theDisc.png"];
CGRect cellRectangle;
    cellRectangle = CGRectMake(-1,self.view.frame.size.height,tmpImage.size.width ,tmpImage.size.height );
    dragger = [[Draggable alloc] initWithFrame:cellRectangle];
    [dragger setImage:tmpImage];
    [dragger setUserInteractionEnabled:YES];

    dragger.layer.anchorPoint = CGPointMake(.5,.5);

    [self.view addSubview:dragger];

我愿意采用新的/更清洁/更正确的方式来做这件事。

提前致谢。

Answer 1

如果角度低于-180或高于180度，则翻转角度。请考虑以下touchesMoved实现：

@implementation RotateView

#define DEGREES_TO_RADIANS(angle) ((angle) / 180.0 * M_PI)

CGFloat angleBetweenLinesInDegrees(CGPoint beginLineA, CGPoint endLineA, CGPoint beginLineB, CGPoint endLineB)
{
    CGFloat a = endLineA.x - beginLineA.x;
    CGFloat b = endLineA.y - beginLineA.y;
    CGFloat c = endLineB.x - beginLineB.x;
    CGFloat d = endLineB.y - beginLineB.y;

    CGFloat atanA = atan2(a, b);
    CGFloat atanB = atan2(c, d);

    // convert radians to degrees
    return (atanA - atanB) * 180 / M_PI;
}

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
    CGPoint curPoint  = [[touches anyObject] locationInView:self];
    CGPoint prevPoint = [[touches anyObject] previousLocationInView:self];

    // calculate rotation angle between two points
    CGFloat angle = angleBetweenLinesInDegrees(self.center, prevPoint, self.center, curPoint);

    // Flip
    if (angle > 180) {
        angle -= 360;
    } else if (angle < -180) {
        angle += 360;
    }

    self.layer.transform = CATransform3DRotate(self.layer.transform, DEGREES_TO_RADIANS(angle), .0, .0, 1.0);
}

@end

在视图的外边界拖动时，它会像旋转轮一样连续旋转。希望它有所帮助。

Answer 2

你有一些问题：

1 - ）

CGPoint curLoc = [touch locationInView:self];

和

firstLoc = [touch locationInView:self];

您正在转换视图，然后询问其中的触摸位置。您无法在旋转视图中获得正确的触摸位置。让它们变得不变。（例如将self.superview放入容器后）

2 - ）

cellRectangle = CGRectMake(-1,self.view.frame.size.height,tmpImage.size.width ,tmpImage.size.height );

通过将self.view.frame.size.height作为CGRect的{{1}}参数传递，您将Draggable实例放在屏幕之外。

CGAffineTransformMakeRotation在180度（-3.14）之后走另一条路

2 个答案: