activityIndicator= [[UIActivityIndicatorViewalloc]initWithFrame:CGRectMake(0,0,80,80)];

[activityIndicatorsetBackgroundColor:[UIColorblackColor]];

[self.viewaddSubview:activityIndicator];

activityIndicator.activityIndicatorViewStyle=UIActivityIndicatorViewStyleWhiteLarge;

//设置背景透明

activityIndicator.alpha=0.6;

//设置背景为圆角矩形

activityIndicator.layer.cornerRadius=4;

activityIndicator.layer.masksToBounds=YES;

//设置显示位置

[activityIndicatorsetCenter:CGPointMake(self.view.frame.size.width/2.0,self.view.frame.size.height/3.0)];