我创建了一个简单UIView的 aUILabel和 a ，UITextField这UIView在屏幕上看起来很好，但是当我触摸UITextField，键盘没有出现。
我正在使用自动布局编程，我认为问题出在UIVIew框架上。我做了一个简单的代码来模拟这个问题，代码中最相关的部分是：
表单输入接口。
//FormInput.h
#import <UIKit/UIKit.h>
@interface FormInput : UIView
@property (nonatomic, strong) NSString *title;
@end
表单输入实现
// FormInput.m
#import "FormInput.h"
@interface FormInput () <UITextFieldDelegate>
@property (nonatomic, strong) UILabel *label;
@property (nonatomic, strong) UITextField *field;
- (void)setuSubviews;
@end
@implementation FormInput
- (id)init
{
self = [super init];
if(!self) return nil;
[self setuSubviews];
return self;
}
- (void)setuSubviews
{
NSDictionary *views = @{
@"label":self.label,
@"field":self.field
};
[self addSubview:self.label];
[self addSubview:self.field];
[self addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|-0-[label(<=120)]-2-[field]-0-|" options:0 metrics:nil views:views]];
[self addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|-0-[label]" options:0 metrics:nil views:views]];
[self addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|-0-[field]" options:0 metrics:nil views:views]];
}
#pragma mark - Lazy properties
- (UILabel *)label
{
if(!_label)
{
_label = [UILabel new];
_label.textColor = [UIColor blackColor];
_label.translatesAutoresizingMaskIntoConstraints = NO;
}
return _label;
}
- (UITextField *)field
{
if(!_field)
{
_field = [UITextField new];
_field.translatesAutoresizingMaskIntoConstraints = NO;
_field.font = [UIFont systemFontOfSize:16];
_field.placeholder = @"enter text here";
_field.keyboardType = UIKeyboardTypeDefault;
_field.keyboardAppearance = UIKeyboardAppearanceDark;
_field.returnKeyType = UIReturnKeyDone;
_field.clearButtonMode = UITextFieldViewModeWhileEditing;
_field.contentVerticalAlignment = UIControlContentVerticalAlignmentCenter;
}
return _field;
}
#pragma mark - Properties setters
- (void)setTitle:(NSString *)title
{
_title = title;
self.label.text = title;
}
@end
视图控制器
#import "ViewController.h"
#import "FormInput.h"
@interface ViewController ()
@property (nonatomic, strong) FormInput *username;
@property (nonatomic, strong) FormInput *email;
- (void)setupLayout;
@end
@implementation ViewController
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
self.view.backgroundColor = [UIColor whiteColor];
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
- (void)viewWillAppear:(BOOL)animated
{
[super viewWillAppear:animated];
// [self setupLayout];
}
- (void)viewDidAppear:(BOOL)animated
{
[super viewDidAppear:animated];
[self setupLayout];
}
#pragma mark - Lazy properties
- (FormInput *)username
{
if(!_username)
{
_username = [FormInput new];
_username.translatesAutoresizingMaskIntoConstraints = NO;
_username.title = @"Username:";
}
return _username;
}
- (FormInput *)email
{
if(!_email)
{
_email = [FormInput new];
_email.translatesAutoresizingMaskIntoConstraints = NO;
_email.title = @"Email:";
}
return _email;
}
#pragma mark - Layout setup
- (void)setupLayout
{
UIButton *btn = [UIButton buttonWithType:UIButtonTypeRoundedRect];
btn.translatesAutoresizingMaskIntoConstraints = NO;
[btn setTitle:@"Button" forState:UIControlStateNormal];
UITextField *field = [UITextField new];
field.translatesAutoresizingMaskIntoConstraints = NO;
field.placeholder = @"Placeholder";
[self.view addSubview:self.username];
[self.view addSubview:self.email];
[self.view addSubview:btn];
[self.view addSubview:field];
NSDictionary *views = @{
@"username" : self.username,
@"email" : self.email,
@"btn" : btn,
@"field" : field
};
[self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|-[username]-|" options:0 metrics:nil views:views]];
[self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|-[email]-|" options:0 metrics:nil views:views]];
[self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|-[btn]-|" options:0 metrics:nil views:views]];
[self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|-[field]-|" options:0 metrics:nil views:views]];
[self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|-30-[username]-30-[email]-30-[btn]-30-[field]" options:0 metrics:nil views:views]];
}
@end