[iOS开发技巧之]iPhone走马灯控件实现

本文来源：http://www.cnblogs.com/KiloNet/archive/2010/09/17/1829155.html

走马灯效果实现原理，就是利用iPhone自带的动画来控制UILable的y轴位置：

代码如下：

//LampText.h
@interface LampText : UILabel {
float motionWidth;
}
@property (nonatomic)   float motionWidth;
@end

//LampText.m
#import "LampText.h"

@implementation LampText
@synthesize motionWidth;

- (id)initWithFrame:(CGRect)frame {
if ((self = [super initWithFrame:frame])) {
motionWidth = 200;
}
return self;
}

- (void)drawRect:(CGRect)rect {

[super drawRect:rect];
float w  = self.frame.size.width;
if (motionWidth>=w) {
return;
}

CGRect frame = self.frame;
frame.origin.x = 320;
self.frame = frame;

[UIView beginAnimations:@"testAnimation" context:NULL];
[UIView setAnimationDuration:8.0f * (w<320?320:w) / 320.0 ];
[UIView setAnimationCurve:UIViewAnimationCurveLinear];
[UIView setAnimationDelegate:self];
[UIView setAnimationRepeatAutoreverses:NO];
[UIView setAnimationRepeatCount: LONG_MAX];

frame = self.frame;
frame.origin.x = -w ;
self.frame = frame;
[UIView commitAnimations];
}

- (void)dealloc {
[super dealloc];
}

@end

//调用：
NSString *title = @"Hi,kilonet, weclome to my blog!";
CGFloat w = [title sizeWithFont:[UIFont fontWithName:@"Arial" size:18]].width;
LampText *titleLabel = [[LampText alloc]initWithFrame:CGRectMake(0, 0, w, 40)];
[titleLabel setBounds:CGRectMake(0, 0, w, 40)];
titleLabel.lineBreakMode = UILineBreakModeClip;
titleLabel.text = title;
titleLabel.textAlignment = UITextAlignmentCenter;
titleLabel.font = [UIFont fontWithName:@"Arial" size:18];
titleLabel.textColor = [UIColor whiteColor];
titleLabel.backgroundColor = [UIColor clearColor];
//[titleLabel sizeToFit];

[self.view addSubview: titleLabel];
[titleLabel release];

其它扩展：

在Navigation里实现跑马灯效果，因为Navigation的宽度限制了，所以须使用下面代码调用：

+(void) showNavTitle:(UIViewController *)controller title:(NSString *)title  {
[Utilitys showNavTitle:controller title:title width:320.0];
}

+(void) showNavTitle:(UIViewController *)controller title:(NSString *)title width:(CGFloat) width {

CGFloat w = [title sizeWithFont:[UIFont fontWithName:@"Arial" size:18]].width;
CGFloat x = 0;
if (w <= width) {
x = (width - w) / 2;
}

LampText *titleLabel = [[LampText alloc]initWithFrame:CGRectMake(x, 0, w, 40)];
titleLabel.motionWidth = width;
titleLabel.lineBreakMode = UILineBreakModeClip;
titleLabel.text = title;
titleLabel.textAlignment = UITextAlignmentCenter;
titleLabel.font = [UIFont fontWithName:@"Arial" size:18];
titleLabel.textColor = [UIColor whiteColor];
titleLabel.backgroundColor = [UIColor clearColor];

UIScrollView *scroll = [[UIScrollView alloc] initWithFrame:CGRectMake(0, 0, width, 40)];
[scroll addSubview:titleLabel];
controller.navigationItem.titleView = scroll;

[titleLabel release];
[scroll release];

}