iphone - 如何滚动标签上的文本(如选框)

Question

我的标签上的文本未完全显示，因此我希望文本在标签上从左到右滚动。请不要建议将 numberoflines 属性作为解决方案。

Answer 1

FWIW，我在 ScrollView 中使用 2 个标签做了类似的事情...

#import <UIKit/UIKit.h>

@interface ScrolledTextView : UIScrollView
{
    UILabel *label1;
    UILabel *label2;

    NSString *_text;
    NSString *newText;

    CGFloat textWidth;

    BOOL animating;
    BOOL needToUpdateText; 
}

@property (nonatomic, copy, setter = setText:) NSString *text;
@property (nonatomic, assign) NSTimeInterval   scrollInterval;
@property (nonatomic, assign) NSTimeInterval   scrollDuration;

- (id) initWithFrame:(CGRect)frame andText : (NSString*) text;

- (void) setText:(NSString *)text;

- (BOOL) textFitsInFrame;

@implementation ScrolledTextView

@synthesize text = _text;
@synthesize scrollDuration;
@synthesize scrollInterval;

- (void) adjustLabelsForNewText : (NSString*) text andParentFrame : (CGRect) frame
{
    _text = [NSString stringWithFormat:@"%@  ", text];

    CGSize textSize = [[self text] sizeWithFont:[label1 font]     constrainedToSize:CGSizeMake(CGFLOAT_MAX, CGFLOAT_MAX) lineBreakMode:UILineBreakModeClip];
    [self setContentSize:CGSizeMake(textSize.width * 2, textSize.height)];

    textWidth = textSize.width;

    [label1 setFrame:CGRectMake(0.0, 0.0, textWidth, frame.size.height)];
    [label1 setText:[self text]];

    if([self textFitsInFrame])
    {
        [label2 removeFromSuperview];
    }
    else 
    {
        [label2 setFrame:CGRectMake([label1 frame].size.width, 0.0, textWidth, frame.size.height)];
        [label2 setText:[self text]];

        if( ! [[self subviews] containsObject:label2])
        {
            [self addSubview:label2];
        }

        [self beginScrolling];
    }
}

- (id) initWithFrame:(CGRect)frame andText : (NSString*) text
{
    self = [super initWithFrame:frame];
    if (self) {
        [self setClipsToBounds:YES];

        animating = NO;
        needToUpdateText = NO;

        [self setScrollDuration:10.0];
        [self setScrollInterval:2.0];

        label1 = [UILabel new];
        label2 = [UILabel new];

        [label1 setBackgroundColor:[UIColor clearColor]];
        [label2 setBackgroundColor:[UIColor clearColor]];

        [self addSubview:label1];

        [self adjustLabelsForNewText:text andParentFrame:frame];        
    }

    return self;
}

- (void)animationDidStop:(NSString *)animationID finished:(NSNumber *)finished context:(void *)context
{
    if(needToUpdateText)
    {
        animating = NO;
        needToUpdateText = NO;
        [self adjustLabelsForNewText:@"" andParentFrame:[self frame]];
        [self adjustLabelsForNewText:newText andParentFrame:[self frame]];
        newText = nil;

        return;
    }

    [self setContentOffset:CGPointMake(0.0, 0.0)];
    [self beginScrolling];
}

- (void) beginScrolling
{
    animating = YES;

    [UIView beginAnimations:nil context:nil];
    [UIView setAnimationDuration:[self scrollDuration]];
    [UIView setAnimationDelay:[self scrollInterval]];
    [UIView setAnimationDelegate:self];
    [UIView setAnimationDidStopSelector:@selector(animationDidStop:finished:context:)];
    [UIView setAnimationCurve:UIViewAnimationCurveLinear];

    [self setContentOffset:CGPointMake(textWidth, 0.0)];

    [UIView commitAnimations];
}

- (BOOL) textFitsInFrame
{
    return textWidth <= [self frame].size.width;
}

- (void) setText:(NSString *)text
{
    if(animating)
    {
        newText = text;
        needToUpdateText = YES;
    }
    else 
    {
        [self adjustLabelsForNewText:text andParentFrame:[self frame]];
    }
}