iPhone – 如何做双圆形滑块(时钟像功能)

CGContextAddArc(imageCtx,self.frame.size.width/2,self.frame.size.height/2,radius,ToRad(self.angle),0);

第一个零(0)是起点,所以你想在这里使用不同的角度

CGContextAddArc(imageCtx,ToRad(self.startAngle),ToRad(self.endAngle),0);

(你当然需要你头上的那两个ivar)

编辑：这是编辑的代码,用于查找最近的旋钮并将其锁定以进行修改.旧代码没有锁定它,因此它会在从一个旋钮悬停到另一个旋钮时发生变化.
首先在你的实现上面添加枚举：

enum SliderLockType {
    SliderLockedNone = 0,SliderLockedStart,SliderLockedEnd
};

#pragma mark - Implementation -

@implementation TBCircularSlider
enum SliderLockType sliderLock;

// … some code here …
   //Initialize the Angle at 0
   //self.startAngle = 0;
   //self.endAngle = 270;

/** Tracking is started **/
-(BOOL)beginTrackingWithTouch:(UITouch *)touch withEvent:(UIEvent *)event{
    [super beginTrackingWithTouch:touch withEvent:event];

    // find nearest knob …
    CGPoint lastPoint = [touch locationInView:self];
    CGPoint pStart = [self centerPointFromAngel:self.startAngle];
    CGPoint pEnd   = [self centerPointFromAngel:self.endAngle];
    float diffA = [self distanceBetween:lastPoint and:pStart];
    float diffB = [self distanceBetween:lastPoint and:pEnd];

    // … and lock it
    if (diffA <= TB_LINE_WIDTH) { // the tolerance is the width of the circle
        sliderLock = SliderLockedStart;
    } else if (diffB <= TB_LINE_WIDTH) {
        sliderLock = SliderLockedEnd;
    }

    //We need to track continuously
    return YES;
}

// continueTrackingWithTouch:withEvent: stays unchanged

/** Track is finished **/
-(void)endTrackingWithTouch:(UITouch *)touch withEvent:(UIEvent *)event{
    [super endTrackingWithTouch:touch withEvent:event];

    // reset the lock before starting a new touch event
    sliderLock = SliderLockedNone;
}

- (CGPoint)centerPointFromAngel:(int)angleInt {
    CGPoint point = [self pointFromAngle:angleInt];
    point.x += TB_LINE_WIDTH/2;
    point.y += TB_LINE_WIDTH/2;
    return point;
}

- (CGFloat)distanceBetween:(CGPoint)p1 and:(CGPoint)p2 {
    CGFloat xDist = (p2.x - p1.x);
    CGFloat yDist = (p2.y - p1.y);
    return sqrt((xDist * xDist) + (yDist * yDist));
}

// … some more code …

- (void)drawTheHandle:(CGContextRef)ctx {

    CGContextSaveGState(ctx);

    //I Love shadows
    CGContextSetShadowWithColor(ctx,CGSizeMake(0,0),3,[UIColor blackColor].CGColor);

    //Get the handle position!
    CGPoint handleCenterA =  [self pointFromAngle: self.startAngle];
    CGPoint handleCenterB =  [self pointFromAngle: self.endAngle];

    //Draw It!
    [[UIColor colorWithWhite:1.0 alpha:0.7]set];
    CGContextFillEllipseInRect(ctx,CGRectMake(handleCenterA.x,handleCenterA.y,TB_LINE_WIDTH,TB_LINE_WIDTH));
    CGContextFillEllipseInRect(ctx,CGRectMake(handleCenterB.x,handleCenterB.y,TB_LINE_WIDTH));

    CGContextRestoreGState(ctx);
}

- (void)movehandle:(CGPoint)lastPoint {

    //Get the center
    CGPoint centerPoint = CGPointMake(self.frame.size.width/2,self.frame.size.height/2);

    //Calculate the direction from the center point to an arbitrary position.
    float currentAngle = AngleFromNorth(centerPoint,lastPoint,NO);
    int angleInt = 360 - floor(currentAngle);

    if (sliderLock == SliderLockedStart) {
        self.startAngle = angleInt;
    } else if (sliderLock == SliderLockedEnd) {
        self.endAngle = angleInt;
    }

    //Redraw
    [self setNeedsDisplay];
}

结果：

EDIT2：如果您希望滑块从小时切换到小时,您可以修改movehandle：方法,如下所示：

int angleInt = (int)(360 - floor(currentAngle)) / 30 * 30; // 360/30 = 12 -> hours

if (sliderLock == SliderLockedStart && angleInt%360 != self.endAngle%360) {
    self.startAngle = angleInt;
} else if (sliderLock == SliderLockedEnd && angleInt%360 != self.startAngle%360) {
    self.endAngle = angleInt;
}