自定义搜索框

SNSearchBar.h
    @interface HMSearchBar : UITextField
    + (instancetype)searchBar;
    @end

SNSearchBar.m
    @implementation HMSearchBar
    - (id)initWithFrame:(CGRect)frame
    {
        self = [super initWithFrame:frame];
        if (self) {
            // 设置背景
            self.background = [UIImage resizedImage:@"searchbar_textfield_background"];

            // 设置内容 -- 垂直居中
            self.contentVerticalAlignment = UIControlContentVerticalAlignmentCenter;

            // 设置左边显示一个放大镜
            UIImageView *leftView = [[UIImageView alloc] init];
            leftView.image = [UIImage imageWithName:@"searchbar_textfield_search_icon"];
            leftView.width = leftView.image.size.width + 10;
            leftView.height = leftView.image.size.height;
            // 设置leftView的内容居中
            leftView.contentMode = UIViewContentModeCenter;
            self.leftView = leftView;

            // 设置左边的view永远显示
            self.leftViewMode = UITextFieldViewModeAlways;

            // 设置右边永远显示清除按钮
            self.clearButtonMode = UITextFieldViewModeAlways;
        }
        return self;
    }

    + (instancetype)searchBar
    {
        return [[self alloc] init];
    }
    @end