ios怎么自定义滑杆效果

本篇内容介绍了"ios怎么自定义滑杆效果"的有关知识，在实际案例的操作过程中，不少人都会遇到这样的困境，接下来就让小编带领大家学习一下如何处理这些情况吧！希望大家仔细阅读，能够学有所成！

先让我们看看效果：

主要实现的代码：

UIImage *thumbWithLevel(float aLevel){    float INSET_AMT = 1.5f;    CGRect baseRect = CGRectMake(0, 0, 40, 100);    CGRect thumbRect = CGRectMake(0, 40, 40, 20);        UIGraphicsBeginImageContext(baseRect.size);    CGContextRef context = UIGraphicsGetCurrentContext();        [[UIColor darkGrayColor] setFill];    CGContextAddRect(context, CGRectInset(thumbRect, INSET_AMT, INSET_AMT));    CGContextFillPath(context);        [[UIColor whiteColor] setStroke];    CGContextSetLineWidth(context, 2);    CGContextAddRect(context, CGRectInset(thumbRect, 2 * INSET_AMT, 2 * INSET_AMT));    CGRect ellipseRect = CGRectMake(0, 0, 40, 40);    [[UIColor colorWithWhite:aLevel alpha:1] setFill];    CGContextAddEllipseInRect(context, ellipseRect);    CGContextFillPath(context);        NSString *numString = [NSString stringWithFormat:@"%0.2f",aLevel];    UIColor *textColor = (aLevel > 0.5) ? [UIColor blackColor] : [UIColor whiteColor];    UIFont *font = [UIFont fontWithName:@"Georgia" size:15];    NSMutableParagraphStyle *style = [[NSMutableParagraphStyle alloc] init];    style.lineBreakMode = NSLineBreakByCharWrapping;    style.alignment = NSTextAlignmentCenter;    NSDictionary *attr = @{NSFontAttributeName:font,NSParagraphStyleAttributeName:style,NSForegroundColorAttributeName:textColor};    [numString drawInRect:CGRectInset(ellipseRect, 0, 6) withAttributes:attr];        [[UIColor grayColor] setStroke];    CGContextSetLineWidth(context, 3);    CGContextAddEllipseInRect(context, CGRectInset(ellipseRect, 2, 2));    CGContextStrokePath(context);        UIImage *theImage = UIGraphicsGetImageFromCurrentImageContext();    UIGraphicsEndImageContext();        return  theImage;}

在这里我们通过context的方法将图片画出了，对于性能有点要求，但是现在应该不在乎这点性能了

- (void)updateThumb{    if ((self.value < 0.98) && (ABS(self.value - previousValue) < 0.1f)) {        return;    }        UIImage *customImg = thumbWithLevel(self.value);    [self setThumbImage:customImg forState:UIControlStateHighlighted];    previousValue = self.value;}

通过滑块的值来使上面的值进行变化，更加的直观

[self setThumbImage:simpleThumb() forState:UIControlStateNormal];  [self addTarget:self action:@selector(startDrag:) forControlEvents:UIControlEventTouchDown];  [self addTarget:self action:@selector(updateThumb) forControlEvents:UIControlEventValueChanged];  [self addTarget:self action:@selector(endDrag:) forControlEvents:UIControlEventTouchUpOutside | UIControlEventTouchUpInside];

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