How to center a UISlider in a UIView?

Question

I am trying to center a UISlider inside a UIView, but it keeps lining up to the left side? Here is the code.

        // Implement loadView to create a view hierarchy programmatically, without using a nib.
    - (UIView *)manufactorSliderWithLabel:(NSString *)sliderText
                                      url:(NSString *)urlPath
                                 callback:(NSString *)method
                                  message:(NSString *)message
                                   status:(NSString *)status {

        // Load the track background
        UIImage *trackImage = [UIImage imageNamed:@"sliderTrack.png"];
        UIImageView *sliderBackground = [[UIImageView alloc] initWithImage:trackImage];

        // Create the superview same size as track backround, and add the background image to it
        UIView *view = [[UIView alloc] initWithFrame:sliderBackground.frame];
        [view addSubview:sliderBackground];
        view.backgroundColor = [UIColor redColor];

        // Add the slider with correct geometry centered over the track
        UISlider* slider = [[UISlider alloc] initWithFrame:sliderBackground.frame];
        CGRect sliderFrame = slider.frame;
        sliderFrame.size.width -= 3; //each "edge" of the track is 23 pixels wide   
        slider.frame = sliderFrame;
        slider.center = sliderBackground.center;
        slider.backgroundColor = [UIColor clearColor];
        [slider setMinimumTrackImage:[UIImage imageNamed:@"sliderMaxMin-02.png"] forState:UIControlStateNormal];
        [slider setMaximumTrackImage:[UIImage imageNamed:@"sliderMaxMin-02.png"] forState:UIControlStateNormal];
        UIImage *thumbImage = [UIImage imageNamed:@"sliderThumbGreen_normal.png"];
        [slider setThumbImage:thumbImage forState:UIControlStateNormal];
        slider.minimumValue = 0.0;
        slider.maximumValue = 1.0;
        slider.continuous = YES;
        slider.value = 0.0;

        slider.url = urlPath;
        slider.message = message;
        slider.socketStatus = status;
        slider.callbackMethod = method;


        // Set the slider action methods
        [slider addTarget:self
                   action:@selector(sliderUp:)
         forControlEvents:UIControlEventTouchUpInside];
        [slider addTarget:self
                   action:@selector(sliderDown:)
         forControlEvents:UIControlEventTouchDown];
        [slider addTarget:self
                   action:@selector(sliderChanged:)
         forControlEvents:UIControlEventValueChanged];

        // Create the label with the actual size required by the text
        // If you change the text, font, or font size by using the "label" property,
        // you may need to recalculate the label's frame.
        NSString *labelText = NSLocalizedString(sliderText, @"SlideToCancel label");
        UIFont *labelFont = [UIFont systemFontOfSize:12];
        CGSize labelSize = [labelText sizeWithFont:labelFont];
        UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(0.0, 0.0, labelSize.width, labelSize.height)];

        // Center the label over the slidable portion of the track
        CGFloat labelHorizontalCenter = slider.center.x + (thumbImage.size.width / 2);
        label.center = CGPointMake(labelHorizontalCenter, slider.center.y);

        // Set other label attributes and add it to the view
        label.textColor = [UIColor blackColor];
        label.textAlignment = UITextAlignmentCenter;
        label.backgroundColor = [UIColor clearColor];
        label.font = labelFont;
        label.text = labelText;
        [view addSubview:label];

        slider.backgroundColor = [UIColor greenColor];

        [view addSubview:slider];



        return view;

    }

Answer 1

如果您想将相应滑块的中心居中，那么请先设置sliderBackground的框架，因为在您的代码中我可以看到您未设置sliderBackground的框架，然后执行

slider.center = sliderBackground.center;