Question

我正在为iPhone实现一个轮子，当它被拖到那个方向时应该顺时针或逆时针转动。尽管如此，但平滑度存在一些误差。有时它看起来很混淆它应该转向哪种方式。有什么帮助吗？

 -(void) touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {

    NSSet *allTouches = [event allTouches];

    int len = [allTouches count]-1;

    UITouch *touch =[[allTouches allObjects] objectAtIndex:len];
    CGPoint location = [touch locationInView:[self superview]];

    xfirst = location.x;
    xnext = xfirst;
    x = [NSNumber numberWithFloat:xfirst];
    yfirst = location.y;
    ynext = yfirst;
    y = [NSNumber numberWithFloat:yfirst];
    //NSLog(@"Touch began for wheel at %f and %f",xfirst, yfirst);
    //NSLog(@"Centre %f and %f",self.center.x, self.center.y);
}

-(void) touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {

    UITouch *touch =[[allTouches allObjects] objectAtIndex:len];
    CGPoint location = [touch locationInView:[self superview]];

    xlast = location.x;
    ylast = location.y;

//dy / dx (gradient)
    if (((ylast-yfirst)/(xlast-xfirst) >= 0.3) || ((ylast-yfirst)/(xlast-xfirst) <= -0.3))
    {

    int seg1 = [self detectSegment:xnext :ynext];
    int seg2 = [self detectSegment:xlast :ylast];
    bool direction = [self isClockWise:seg1 :seg2];
    lastDirection = direction;

    float theAngle = [self getAngle:self.center.x:self.center.y:xfirst:yfirst:xlast:ylast];

    theAngle = theAngle / 6; 

    if (direction == YES)
    {

    }
    else {

        theAngle = -1*theAngle;
    }

    theAngle += totalRadians;   
    float rads = 6.28318531;
    int divAm = 0;
    NSNumberFormatter *formatter = [[NSNumberFormatter alloc] init];
    [formatter setMaximumFractionDigits:0];
    [formatter setRoundingMode: NSNumberFormatterRoundDown];

    float nm = theAngle/rads;
    NSString *numberString = [formatter stringFromNumber:[NSNumber numberWithFloat:nm]];
    [formatter release];
    divAm = [numberString floatValue];
    theAngle = theAngle - (float)(6.28318531*divAm);
    totalRadians = theAngle;
    xnext = xlast;
    ynext = ylast;
    [self rotateImage:theAngle];
    }
}


- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
}

-(float) getAngle: (CGFloat)P1x: (CGFloat)P1y: (CGFloat)P2x: (CGFloat)P2y: (CGFloat)P3x: (CGFloat)P3y {
    float P23 = [self getLength:P2x:P2y:P3x:P3y];
    float P12 = [self getLength:P1x:P1y:P2x:P2y];
    float P13 = [self getLength:P1x:P1y:P3x:P3y];
    return acos((P23*P23 - P12*P12 - P13*P13)/(-2*P12*P13));
}

-(float) getLength: (CGFloat)P1x: (CGFloat)P1y: (CGFloat)P2x: (CGFloat)P2y
{
    return sqrt((P1x-P2x)*(P1x-P2x) + (P1y-P2y)*(P1y-P2y));
}

有什么建议吗？

Answer 1

我有点困惑为什么你要用这么复杂的算法找到角度。我不明白你为什么需要渐变，在计算中使用数字格式有点奇怪。也就是说，你可能有充分的理由做这些事情，所以我建议你简化算法以测试旋转代码;如果仍然需要，可以在以后添加复杂性。从根本上说，你只需要： -

theAngle = atan2( location.y-self.center.y, location.x-self.center.x )

确保滚轮跟踪你的手指。

iPhone车轮运行不顺畅

1 个答案: