有時(shí)候會(huì)遇到UILabel中的內(nèi)容超出長(zhǎng)度，顯示不完全的問(wèn)題。有一種解決方法是通過(guò)動(dòng)畫(huà)字幕來(lái)實(shí)現(xiàn)，比如：
1.字幕向左或者右滾動(dòng)
2.字幕來(lái)回滾動(dòng)
本文以后者為例來(lái)說(shuō)明吧。這里先介紹UIView的通過(guò)Block實(shí)現(xiàn)的Animation以及其參數(shù)控制，最后是實(shí)現(xiàn)滾動(dòng)字幕的代碼。
1. UIView有方便的動(dòng)畫(huà)實(shí)現(xiàn)方式，SDK4.0以上，提供了三個(gè)Block的動(dòng)畫(huà)方式：
+ (void)animateWithDuration:(NSTimeInterval)duration delay:(NSTimeInterval)delay options:(UIViewAnimationOptions)options animations:(void (^)(void))animations completion:(void (^)(BOOL finished))completion __OSX_AVAILABLE_STARTING(__MAC_NA,__IPHONE_4_0);
+ (void)animateWithDuration:(NSTimeInterval)duration animations:(void (^)(void))animations completion:(void (^)(BOOL finished))completion __OSX_AVAILABLE_STARTING(__MAC_NA,__IPHONE_4_0); // delay = 0.0, options = 0
+ (void)animateWithDuration:(NSTimeInterval)duration animations:(void (^)(void))animations __OSX_AVAILABLE_STARTING(__MAC_NA,__IPHONE_4_0); // delay = 0.0, options = 0, completion = NULL
其中第一個(gè)最全面，可以設(shè)置UIViewAnimationOptions來(lái)控制動(dòng)畫(huà)的參數(shù)，比如重復(fù)，自動(dòng)reverse之類(lèi)的。
2. UIViewAnimationOptions具體定義如下：
enum {
UIViewAnimationOptionLayoutSubviews??????????? = 1 <<? 0,
UIViewAnimationOptionAllowUserInteraction????? = 1 <<? 1, // turn on user interaction while animating
UIViewAnimationOptionBeginFromCurrentState???? = 1 <<? 2, // start all views from current value, not initial value
UIViewAnimationOptionRepeat??????????????????? = 1 <<? 3, // repeat animation indefinitely
UIViewAnimationOptionAutoreverse?????????????? = 1 <<? 4, // if repeat, run animation back and forth
UIViewAnimationOptionOverrideInheritedDuration = 1 <<? 5, // ignore nested duration
UIViewAnimationOptionOverrideInheritedCurve??? = 1 <<? 6, // ignore nested curve
UIViewAnimationOptionAllowAnimatedContent????? = 1 <<? 7, // animate contents (applies to transitions only)
UIViewAnimationOptionShowHideTransitionViews?? = 1 <<? 8, // flip to/from hidden state instead of adding/removing
UIViewAnimationOptionCurveEaseInOut??????????? = 0 << 16, // default
UIViewAnimationOptionCurveEaseIn?????????????? = 1 << 16,
UIViewAnimationOptionCurveEaseOut????????????? = 2 << 16,
UIViewAnimationOptionCurveLinear?????????????? = 3 << 16,
UIViewAnimationOptionTransitionNone??????????? = 0 << 20, // default
UIViewAnimationOptionTransitionFlipFromLeft??? = 1 << 20,
UIViewAnimationOptionTransitionFlipFromRight?? = 2 << 20,
UIViewAnimationOptionTransitionCurlUp????????? = 3 << 20,
UIViewAnimationOptionTransitionCurlDown??????? = 4 << 20,
UIViewAnimationOptionTransitionCrossDissolve?? = 5 << 20,
UIViewAnimationOptionTransitionFlipFromTop???? = 6 << 20,
UIViewAnimationOptionTransitionFlipFromBottom? = 7 << 20,
};
typedef NSUInteger UIViewAnimationOptions;
3. 本文實(shí)現(xiàn)方法就是使用Animation with Block的方式來(lái)實(shí)現(xiàn)UILabel來(lái)回滾動(dòng)。代碼如下：
-(void)startAnimationIfNeeded{
//取消、停止所有的動(dòng)畫(huà)
[self.aUILabel.layer removeAllAnimations];
CGSize textSize = [self.aUILabel.text sizeWithFont:self.aUILabel.font];
CGRect lframe = self.aUILabel.frame;
lframe.size.width = textSize.width;
self.aUILabel.frame = lframe;
const float oriWidth = 180;
if (textSize.width > oriWidth) {
float offset = textSize.width - oriWidth;
[UIView animateWithDuration:3.0
delay:0
options:UIViewAnimationOptionRepeat //動(dòng)畫(huà)重復(fù)的主開(kāi)關(guān)
|UIViewAnimationOptionAutoreverse //動(dòng)畫(huà)重復(fù)自動(dòng)反向，需要和上面這個(gè)一起用
|UIViewAnimationOptionCurveLinear //動(dòng)畫(huà)的時(shí)間曲線(xiàn)，滾動(dòng)字幕線(xiàn)性比較合理
animations:^{
self.aUILabel.transform = CGAffineTransformMakeTranslation(-offset, 0);
}
completion:^(BOOL finished) {
}
];
}
}
