解决 UIAlertView 多次 弹出 问题

static UIAlertView *_alertView = nil;
+ (void)showAlert:(NSString *)aTitle message:(NSString *)aMessage delegate:(id<UIAlertViewDelegate>)aDelegate cancelButtonTitle:(NSString *)cancelButtonTitle otherButtonTitles:(NSString *)otherButtonTitles, ...{

    if (_alertView.isVisible) {
        return;
    }
    if (_alertView != nil) {
        [_alertView release],_alertView = nil;
    }
    _alertView = [[UIAlertView alloc] initWithTitle:aTitle message:aMessage delegate:aDelegate cancelButtonTitle:cancelButtonTitle otherButtonTitles:nil];
    if (otherButtonTitles != nil) {
        va_list args;
        va_start(args, otherButtonTitles);
        NSString* arg = nil;
        [_alertView addButtonWithTitle:otherButtonTitles];
        while ( ( arg = va_arg( args, NSString*) ) != nil ) {
            [_alertView addButtonWithTitle:arg];
        }
        va_end(args);
    }
    [_alertView show];
}