UIProgressView顾名思义用来显示进度的，如音乐，视频的播放进度，和文件的上传下载进度等。
下面以一个简单的实例来介绍UIprogressView的使用。
@interface ActivityViewController : UIViewController
{
UIProgressView *proView;
double proValue;
NSTimer *timer;
}
@property(nonatomic, retain) UIProgressView *proView;
-(IBAction)btnStartClick;
@implementation ActivityViewController
@synthesize proView;
#pragma mark - View lifecycle
-(IBAction)btnStartClick
{
proValue=0;
timer = [NSTimerscheduledTimerWithTimeInterval:1target:selfselector:@selector(changeProgress) userInfo:nilrepeats:YES]; //利用计时器，每隔1秒调用一次（changeProgress）
}
-(void)changeProgress
{
proValue += 1.0; ／／改变proValue的值
if(proValue > 5)
{
//停用计时器
[timer invalidate];
}
else
{
[proViewsetProgress:(proValue / 5)];//重置进度条
}
}
- (void)viewDidLoad
{
proView = [[UIProgressViewalloc] initWithFrame:CGRectMake(100, 100, 150, 20)];
[proViewsetProgressViewStyle:UIProgressViewStyleDefault]; //设置进度条类型
[self.viewaddSubview:proView];
[superviewDidLoad];