最近在项目中遇到需要自定义搜索框的问题，试了很多方法，今天才总算解决了，积累经验，总结一番。
比如这种样式

屏幕快照 2016-08-13 下午3.56.23.png

代码如下

- (void)createSearchBar{
    searchBar = [[UISearchBar alloc] initWithFrame:CGRectMake((self.view.frame.size.width-300)/2, 100, 300, 40)];
    searchBar.delegate = self;
    searchBar.placeholder = [NSString stringWithCString:"搜索" encoding:NSUTF8StringEncoding];
    //设置searchBar的背景色
    UIImage * searchBarBg1 = [self GetImageWithColor:[UIColor whiteColor] andHeight:40];
    [searchBar setBackgroundImage:searchBarBg1];
    [searchBar setBackgroundColor:[UIColor clearColor]];
    //设置输入框的背景色
    UIImage * searchBarBg2 = [self GetImageWithColor:[UIColor greenColor] andHeight:40];
    [searchBar setSearchFieldBackgroundImage:searchBarBg2 forState:UIControlStateNormal];
    //设置字体颜色/大小，和圆角边框
    UITextField *searchField = [searchBar valueForKey:@"_searchField"];
    searchField.textColor = [UIColor grayColor];
    [searchField setValue:[UIColor grayColor] forKeyPath:@"_placeholderLabel.textColor"];
    searchField.font = [UIFont systemFontOfSize:17];
    searchField.layer.cornerRadius = searchBar.frame.size.height/2;
    searchField.layer.masksToBounds = YES;
    [searchBar setContentMode:UIViewContentModeLeft];
    [self.view addSubview:searchBar];
    
}
//生成图片
- (UIImage*) GetImageWithColor:(UIColor*)color andHeight:(CGFloat)height
{
    CGRect r= CGRectMake(0.0f, 0.0f, 1.0f, height);
    UIGraphicsBeginImageContext(r.size);
    CGContextRef context = UIGraphicsGetCurrentContext();
    
    CGContextSetFillColorWithColor(context, [color CGColor]);
    CGContextFillRect(context, r);
    
    UIImage *img = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    
    return img;
}