如何在iphone应用程序中实现Ticker

假设“Ticker”是指水平滚动的文本:

股票代码基本上只是一个文本字符串,它通过不断改变x坐标来移动。查看以下有关如何显示标签的简单教程:

http://knol.google.com/k/iphone-sdk-helloworld

然后,您可以使用NSTimer调用一个方法来连续更新标签x坐标,从而为其设置动画。

#import <UIKit/UIKit.h>


@interface TickerScrollView : UIScrollView {

    UILabel *textLabel;

}

- (void)displayText:(NSString *)string;
- (void)clearTicker;

@property (nonatomic, retain, readwrite) UILabel *textLabel;

@end

////


#import "TickerScrollView.h"

@interface TickerScrollView()

- (void)initialiseTextLabel;
- (void)clearTicker;

- (void)beginAnimation;

@end


@implementation TickerScrollView

- (id)initWithFrame:(CGRect)frame {
    if ((self = [super initWithFrame:frame])) {

        // Initialization code
        [self setFrame: frame];

        [self setBounces: NO];
        [self setUserInteractionEnabled:NO];

        [self setShowsVerticalScrollIndicator:NO];
        [self setShowsHorizontalScrollIndicator:NO];

        [self initialiseTextLabel];

    }
    return self;
}

- (void)initialiseTextLabel {

    textLabel = [[[UILabel alloc] initWithFrame:self.bounds] autorelease];
    [textLabel setTextAlignment:UITextAlignmentLeft];
    [textLabel setNumberOfLines:1];
    [textLabel sizeToFit];

    [self addSubview:textLabel];
    [self sendSubviewToBack:textLabel];

    [self setScrollEnabled:YES];

}

- (void)displayText:(NSString *)string {

    [self clearTicker];

    [textLabel setText:string];
    [textLabel sizeToFit];

    [self setContentSize:textLabel.frame.size];

    [self beginAnimation];

}

- (void)clearTicker {

    [textLabel setText:@""];
    [textLabel sizeToFit];

    CGPoint origin = CGPointMake(0, 0);
    [self setContentOffset:origin];

}

- (void)beginAnimation {

    CGFloat text_width = textLabel.frame.size.width;
    CGFloat display_width = self.frame.size.width;

    if ( text_width > display_width ) {

        CGPoint origin = CGPointMake(0, 0);
        [self setContentOffset:origin];

        CGPoint terminal_origin = CGPointMake(textLabel.frame.size.width - self.frame.size.width, textLabel.frame.origin.y);
        float duration = (text_width - display_width)/50;

        [UIView beginAnimations:nil context:NULL];

        [UIView setAnimationCurve:UIViewAnimationCurveLinear];
        [UIView setAnimationDelay:1.0];
        [UIView setAnimationDuration:duration];

        [self setContentOffset:terminal_origin];

        [UIView commitAnimations];

    }

}

/*
// Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.
- (void)drawRect:(CGRect)rect {
    // Drawing code
}
*/

- (void)dealloc {

    [textLabel release];
    [super dealloc];

}

@synthesize textLabel;

@end