UILabel auto scroll like a marquee

问题

I am trying I make a UI label auto scroll the text that is inside it like a marquee. The below code works depending on what kind of text/content I throw at it. I can't tell what works and what does not. What happens is that the label does not show anything, then suddenly scrolls the text at an extremely high speed that you can't read it.

For some reason, this works perfectly on the iPhone but not on the iPad. I am guessing because the text I am putting at the iPhone is always way bigger than the Uilabel's size?

Here is the code:

self.currentTrack.textColor = [UIColor colorWithRed:15.0/255.0 green:176.0/255.0 blue:223.0/255.0 alpha:1];
self.currentTrack.labelSpacing = 35; // distance between start and end labels
self.currentTrack.pauseInterval = 1.7; // seconds of pause before scrolling starts again
self.currentTrack.scrollSpeed = 30; // pixels per second
self.currentTrack.textAlignment = NSTextAlignmentCenter; // centers text when no auto-scrolling is applied
self.currentTrack.fadeLength = 12.f;
self.currentTrack.scrollDirection = CBAutoScrollDirectionLeft;
[self.currentTrack observeApplicationNotifications];

}

回答1:

Here is the code:

AutoScrollLabel, extended from UIView (code provided below) has an instance method to set text (setLabelText). The text provided will auto scroll only if the length of the text is bigger than the width of the AutoScrollLabel view.

Eg:

AutoScrollLabel *autoScrollLabel = [[AutoScrollLabel alloc] initWithFrame:CGRectMake(0, 0, 150, 25)];
[autoScrollLabel setLabelText:@"Some lengthy text to be scrolled"];

Note: You can make changes in setLabelText: Method implementation to support Attributed Text (use appropriate methods to find size of Attributed Text)

*** AutoScrollLabel.h

@interface AutoScrollLabel : UIView {
    UILabel *textLabel;
    NSTimer *timer;
}

- (void) setLabelText:(NSString*) text;
- (void) setLabelFont:(UIFont*)font;
- (void) setLabelTextColor:(UIColor*)color;
- (void) setLabelTextAlignment:(UITextAlignment)alignment;
@end

**** AutoScrollLabel.m

#import "AutoScrollLabel.h"
#import <QuartzCore/QuartzCore.h>

@implementation AutoScrollLabel

- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
       // Initialization code
        self.clipsToBounds = YES;
        self.autoresizesSubviews = YES;

        textLabel = [[UILabel alloc] initWithFrame:CGRectMake(0, 0, frame.size.width,   frame.size.height)];
        textLabel.backgroundColor = [UIColor clearColor];
        textLabel.textColor = [UIColor blackColor];
        textLabel.textAlignment = UITextAlignmentRight;
        [self addSubview:textLabel];
    }
    return self;
}

-(void) setLabelText:(NSString*) text {

    textLabel.text  = text;
    CGSize textSize = [text sizeWithFont:textLabel.font];

    if(textSize.width > self.frame.size.width) {
        textLabel.frame = CGRectMake(0, 0, textSize.width, self.frame.size.height);
    }
    else {
        textLabel.frame = CGRectMake(0, 0, self.frame.size.width, self.frame.size.height);
    }

    if(textLabel.frame.size.width > self.frame.size.width) {

      [timer invalidate];
      timer = nil;
      CGRect frame = textLabel.frame;
      frame.origin.x = self.frame.size.width-50;
      textLabel.frame = frame;
      timer = [NSTimer scheduledTimerWithTimeInterval:0.1 target:self selector:@selector(moveText) userInfo:nil repeats:YES];
    }
    else {
        [timer invalidate];
        timer = nil;
    }
  }

-(void) moveText {

    if(textLabel.frame.origin.x < textLabel.frame.size.width-2*textLabel.frame.size.width) {
        CGRect frame = textLabel.frame;
        frame.origin.x = self.frame.size.width;
        textLabel.frame = frame;
    }
    [UIView beginAnimations:nil context:nil];
    CGRect frame = textLabel.frame;
    frame.origin.x -= 5;
    textLabel.frame = frame;
    [UIView commitAnimations];

}

- (void) setLabelFont:(UIFont*)font {
    textLabel.font = font;
}

- (void) setLabelTextColor:(UIColor*)color {
    textLabel.textColor = color;
}

- (void) setLabelTextAlignment:(UITextAlignment)alignment {
    textLabel.textAlignment = alignment;
}

回答2:

For Swift5

set top of your UILabel equal to superview bottom, and then use this code:

 func createAnimationLbl() -> CAAnimation {
        let animation = CABasicAnimation(keyPath: "transform.translation.y")
        animation.fromValue = 0
        animation.toValue = -(self.view.frame.height )
        animation.duration = 15
        animation.repeatCount = Float.infinity //times of scrolling, infinity for unlimited times.
        
        animation.timingFunction =  CAMediaTimingFunction.init(name: CAMediaTimingFunctionName.linear)
        animation.fillMode = CAMediaTimingFillMode.forwards
        animation.isRemovedOnCompletion = false
        return animation
        
    }

then in your viewWillAppear call it as below:

self.aboutLbl.layer.add(createAnimationLbl(), forKey: nil)

来源：https://stackoverflow.com/questions/26194701/uilabel-auto-scroll-like-a-marquee

标签

ios

uilabel