我想在滑动过程中更改 UISlider 缩略图。
基本上是根据值来设置thumbImage。

想法是根据值旋转图像并将其设置为拇指。
所以我尝试通过覆盖

-(BOOL)continueTrackingWithTouch:(UITouch *)touch withEvent:(UIEvent *)event
 [self setThumbImage:[self imageRotatedByDegrees:50] forState:UIControlStateHighlighted];

当我向我的 slider 添加一个 Action 时，我也尝试了同样的事情。 不幸的是，在这两种实现中，图像都消失了。
你认为我这样做有可能实现吗？ 如果否，请解释并建议另一种方法(希望不会自定义和替换整个 slider )
如果是，我将非常感谢代码示例。 The more close answer that I found here

非常感谢。

最佳答案

我在我的代码中发现了一个错误。显然我在调用 CGContextDrawImage 之前发布了其中一张图片。 (我仍然需要改进我的 GUI 外观以使其更漂亮，例如，为了按照我的计划制作轨道图像，我将原始图像设为透明并添加了我需要的 subview 。)

- (id)initWithFrame:(CGRect)frame
 {
self = [super initWithFrame:frame];
if (self) {
    self.thumbImage = [self imageWithImage:[UIImage imageNamed:@"IconForSlider.png"] scaledToSize:CGSizeMake(frame.size.height, frame.size.height)];
    size = self.thumbImage.size.height;
    [self setThumbImage:[self imageRotatedByDegrees:0] forState:UIControlStateNormal];
    [self addTarget:self action:@selector(changeValue) forControlEvents:UIControlEventValueChanged];

}
return self;
}

-(void)changeValue{
NSLog(@"ChangeValue");
[self setThumbImage:(UIImage *)[self imageRotatedByDegrees:(self.value * 100*(10/9))] forState:UIControlStateHighlighted];
[self setThumbImage:(UIImage *)[self imageRotatedByDegrees:(self.value * 100*(10/9))] forState:UIControlStateNormal];
 }

#pragma mark ImageResize
- (UIImage *)imageWithImage:(UIImage *)image scaledToSize:(CGSize)newSize {
UIGraphicsBeginImageContextWithOptions(newSize, NO, 0.0);
[image drawInRect:CGRectMake(0, 0, newSize.width, newSize.height)];
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage;
 }

 #pragma mark Rotate

- (UIImage *)imageRotatedByDegrees:(float)degrees
 {
NSLog(@"ImageRotateByDegres");
static float Prc = 0.6;
degrees = (degrees > 90)? 90: degrees;

UIView *rotatedViewBox = [[UIView alloc] initWithFrame:CGRectMake(0,0,size,size)];
CGSize rotatedSize = rotatedViewBox.frame.size;

 // Create the bitmap context

UIGraphicsBeginImageContextWithOptions(rotatedSize , NO, 0.0);
CGContextRef bitmap = UIGraphicsGetCurrentContext();
UIColor *color = [self.colorsArray objectAtIndex:lround(self.value*100)];
[color setFill];
CGContextRef bitmap = UIGraphicsGetCurrentContext();

[[UIColor colorWithRed:((139 + (116/100)*self.value*100)/255.0) green:141/255.0f blue:149/255.0f alpha:1.0f] setFill];
// Move the origin to the middle of the image so we will rotate and scale around the center.
CGContextTranslateCTM(bitmap, rotatedSize.width/2, rotatedSize.height/2);

// Rotate the image context
CGContextRotateCTM(bitmap,DEGREES_TO_RADIANS(degrees));

CGContextClipToMask(bitmap, CGRectMake(-1*size/ 2, -1*size / 2, size, size), [self.thumbImage CGImage]);
CGContextAddRect(bitmap, CGRectMake(-1*size/ 2, -1*size / 2, size, size));
CGContextDrawPath(bitmap,kCGPathFill);
 //Prc and 1.07 are for better view
CGContextDrawImage(bitmap, CGRectMake(-1.07*size/2*Prc, -1*size/2*Prc,size*Prc,size*Prc), [[UIImage imageNamed:@"ActiveIcon.png"]CGImage]);

UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage;

 }

在这个链接的帮助下，我为我的 slider 创建了一个颜色数组 Get Pixel Color of Uiimage

- (UIColor *)GetColorAtValue:(float)value{

long pixelInfo = (long)floorf(_sliderImage.size.width  * _sliderImage.size.height/2 + _sliderImage.size.width * value) * 4  ;

UInt8 red = data[pixelInfo];         // If you need this info, enable it
UInt8 green = data[(pixelInfo + 1)]; // If you need this info, enable it
UInt8 blue = data[pixelInfo + 2];    // If you need this info, enable it
//UInt8 alpha = data[pixelInfo + 3];     // I need only this info for my maze game
//CFRelease(pixelData);

UIColor* color = [UIColor colorWithRed:red/255.0f green:green/255.0f blue:blue/255.0f alpha:1]; // The pixel color info

return color;

关于ios - 滑动时更改 UIslider 缩略图，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/22468388/