IOS之活动指示器ActivityIndicatorView和进度条ProgressView
。进度条ProgressView不言而喻，就是显示进度的加载条。现在我们来模拟下载的过程。点击下面的Download按钮，使指示器ActivityIndicatorView动起来，并且使进度条ProgressView的进度每隔0.1s使进度加上1%，当进度达到100%时，停止指示器ActivityIndicatorView和进度条ProgressView。

?

//单击按钮触发的事件- (IBAction)startProgress:(UIButton *)sender {    //isDownloading初始状态为NO    if(isDownloading==NO){        self.progressView.progress = 0;        timer = [NSTimer scheduledTimerWithTimeInterval:0.1                                                 target:self                                               selector:@selector(startDownload)                                               userInfo:nil                                                repeats:YES];        NSLog(@"initialize timer finish");        isDownloading=YES;        [self.indicator startAnimating];    }}//自定义模拟下载的事件，对应NSTimer绑定的事件-(void)startDownload{    self.progressView.progress = self.progressView.progress + 0.01;    NSLog(@"progress = %f",self.progressView.progress);    if(self.progressView.progress==1){        [timer invalidate];        NSLog(@"download finish");        [self.indicator stopAnimating];        isDownloading=NO;    }}

?