1、去除灰色边框
self.mySearchBar.barTintColor = [UIColor whiteColor];
self.mySearchBar.layer.borderWidth = 1;
self.mySearchBar.layer.borderColor = [UIColor whiteColor].CGColor;
self.mySearchBar.layer.cornerRadius = 15;
self.mySearchBar.layer.masksToBounds = YES;
self.mySearchBar.backgroundColor = [UIColor clearColor];
2、placeHolder字体的颜色和大小
UITextField * searchField = [self.mySearchBar valueForKey:@"_searchField"];
[searchField setValue:[UIColor redColor] forKeyPath:@"_placeholderLabel.textColor"];
[searchField setValue:[UIFont boldSystemFontOfSize:13] forKeyPath:@"_placeholderLabel.font"];
