UIActivityIndicatorView 使用

//开始处理图片，显示指示器
-(IBAction)startEffectChange:(id)sender
{
    waitView.hidden = NO;
    //停止用户交互
    self.view.userInteractionEnabled=NO;
    wait = [[UIActivityIndicatorView alloc]initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];
    waitView.layer.cornerRadius = 5;
    [self.view addSubview:waitView];
    [wait startAnimating];
    //异步执行的方法
    [self performSelectorInBackground:@selector(effectChangeOnBg:) withObject:sender];
}

-(void)effectChangeOnBg:(id)sender
{
    //调用主线程的方法，更新UI
    [self performSelectorOnMainThread:@selector(endEffectChange) withObject:nil waitUntilDone:YES];
}
#pragma mark -  处理完毕

//借书处理图片，删除指示器的显示
-(void)endEffectChange{
    //开启用户交互
    [wait stopAnimating];
    self.view.userInteractionEnabled = YES; 
    [waitView removeFromSuperview];
}