IOS——按圆圈排布照片

摘自 Ipad应用开发实践指南

- (void)setAngle:(CGFloat)angle{
    CGPoint center = CGPointMake(CGRectGetMidX([self bounds]), CGRectGetMidY([self bounds]));
    
    CGFloat radiusX = MIN([self bounds].size.width, [self bounds].size.height) * 0.35;
    CGFloat radiusY = radiusX;
    
    NSInteger cellCount = [[self dataSource] wheelViewNumberOfCells:self];
    float angleToAdd = 360.0f / cellCount;
    
    for (NSInteger index = 0; index < cellCount; index ++) {
        XYWheelViewCell *cell = [[self dataSource] wheelView:self cellAtIndex:index];
        if ([cell superview] == nil) {
            [self addSubview:cell];
        }
        
        float angleInRadians = (angle + 180.0) * M_PI / 180.0f;
        
        float xPosition = center.x + (radiusX * sinf(angleInRadians)) - (CGRectGetWidth([cell frame]) / 2);
        float yPosition = center.y + (radiusY * cosf(angleInRadians)) - (CGRectGetHeight([cell frame]) / 2);
        
        float scale = 0.75f + 0.25f * (cosf(angleInRadians) + 1.0);
        if ([self style] == WheelViewStyleCarousel) {
            [cell setTransform:CGAffineTransformScale(CGAffineTransformMakeTranslation(xPosition, yPosition), scale, scale)];
            [cell setAlpha:(0.3f + 0.5f * (cosf(angleInRadians) + 1.0))];
        }else{
            [cell setTransform:CGAffineTransformMakeTranslation(xPosition, yPosition)];
            [cell setAlpha:1.0];
        }
        
        [[cell layer] setZPosition:scale];
        
        angle += angleToAdd;
    }
}