1 #import "UINoMidSearchBar.h"
 2 @implementation UINoMidSearchBar
 3 
 4 - (instancetype)initWithFrame:(CGRect)frame{
 5     
 6     self = [super initWithFrame:frame];
 7     if (self) {
 8         self.hasCentredPlaceholder = YES;
 9     }
10     return self;
11 }
12 
13 -(void)setHasCentredPlaceholder:(BOOL)hasCentredPlaceholder{
14 
15     _hasCentredPlaceholder = hasCentredPlaceholder;
16     SEL centerSelector = NSSelectorFromString([NSString stringWithFormat:@"%@%@", @"setCenter", @"Placeholder:"]);
17     if ([self respondsToSelector:centerSelector]){
18     
19         NSMethodSignature *signature = [[UISearchBar class] instanceMethodSignatureForSelector:centerSelector];
20     
21         NSInvocation *invocation = [NSInvocation invocationWithMethodSignature:signature];
22         [invocation setTarget:self];
23         [invocation setSelector:centerSelector];
24         [invocation setArgument:&_hasCentredPlaceholder atIndex:2];
25         [invocation invoke];
26     }
27 }
28 
29 @end

 1 #import "ViewController.h"
 2 #import "UINoMidSearchBar.h"
 3 @interface ViewController ()
 4 
 5 @property(strong,nonatomic)UINoMidSearchBar *testSearchBar;//搜索框
 6 
 7 @end
 8 
 9 @implementation ViewController
10 
11 - (void)viewDidLoad {
12     [super viewDidLoad];
13     self.view.backgroundColor = [UIColor whiteColor];
14     
15     //创建搜索框
16     self.testSearchBar = [[UINoMidSearchBar alloc] initWithFrame:CGRectMake(0, 200, 320, 50)];
17     self.testSearchBar.placeholder = @"窈窕淑女";
18     self.testSearchBar.hasCentredPlaceholder = NO;// 占位字符默认非居中
19     //[self.testSearchBar setImage:[UIImage imageNamed:@""] forSearchBarIcon:UISearchBarIconSearch state:UIControlStateNormal];// 修改搜索图片（放大镜）
20     //[[[self.testSearchBar.subviews objectAtIndex:0].subviews objectAtIndex:1] setTintColor:[UIColor greenColor]];// 设置光标颜色
21     //self.testSearchBar.searchBarStyle = UISearchBarStyleMinimal;// 祛除边框
22     [self.testSearchBar setKeyboardType:UIKeyboardTypeEmailAddress];
23     [self.view addSubview:_testSearchBar];
24     
25 }
26 
27 
28 @end

运行效果：

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