//左右轨的图片    UIImage *stetchLeftTrack= [UIImage imageNamed:@"brightness_bar.png"];    UIImage *stetchRightTrack = [UIImage imageNamed:@"brightness_bar.png"];    //滑块图片    UIImage *thumbImage = [UIImage imageNamed:@"mark.png"];        UISlider *sliderA=[[UISlider alloc]initWithFrame:CGRectMake(30, 320, 257, 7)];    sliderA.backgroundColor = [UIColor clearColor];    sliderA.value=1.0;    sliderA.minimumValue=0.7;    sliderA.maximumValue=1.0;        [sliderA setMinimumTrackImage:stetchLeftTrack forState:UIControlStateNormal];    [sliderA setMaximumTrackImage:stetchRightTrack forState:UIControlStateNormal];    //注意这里要加UIControlStateHightlighted的状态，否则当拖动滑块时滑块将变成原生的控件    [sliderA setThumbImage:thumbImage forState:UIControlStateHighlighted];    [sliderA setThumbImage:thumbImage forState:UIControlStateNormal];    //滑块拖动时的事件    [sliderA addTarget:self action:@selector(sliderValueChanged:) forControlEvents:UIControlEventValueChanged];    //滑动拖动后的事件    [sliderA addTarget:self action:@selector(sliderDragUp:) forControlEvents:UIControlEventTouchUpInside];        [self.view addSubview:sliderA];