UITextField 的使用

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1.UITextField 的基本设置

   UITextField *passTf = [[UITextField alloc]init];//初始化    passTf.placeholder = @"密码";//填充背景提示    passTf.secureTextEntry = YES; //设置为密码格式，默认是明文格式    passTf.delegate = self;//设置代理，能够使用协议中的方法实现操作    passTf.clearButtonMode = UITextFieldViewModeWhileEditing;//编辑时尾部出现 x , 能够清空文本    [父视图 addSubview:passTf]; //添加视图    [passTf mas_makeConstraints:^(MASConstraintMaker *make) {//此处运用了Masonry第三方框架实现自动布局       make.edges.mas_equalTo(UIEdgeInsetsMake(0, 20, 0, 20));    }];

 textField.returnKeyType = UIReturnKeyDefault;//默认是return

2.UITextField的文本限制以及字符长度

//定义字符类型kAlphaNum

#define kAlphaNum @"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"-(BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string{

  //限制字符类型

    NSCharacterSet *cs;    cs = [[NSCharacterSet characterSetWithCharactersInString:kAlphaNum]invertedSet];        NSString *filtered = [[string componentsSeparatedByCharactersInSet:cs]componentsJoinedByString:@""]; //按cs分离出数组,数组按@""分离出字符串        BOOL canChange = [string isEqualToString:filtered];        if (!canChange) {        UIAlertController *alert = [UIAlertController alertControllerWithTitle:@"⚠️警告" message:@"输入错误！请输入字母或数字" preferredStyle:UIAlertControllerStyleAlert];        [alert addAction:[UIAlertAction actionWithTitle:@"确定" style:UIAlertActionStyleDefault handler:^(UIAlertAction * _Nonnull action) {                    }]];        [self presentViewController:alert animated:YES completion:nil];    }    //限制字符长度    NSString * toBeString = [textField.text stringByReplacingCharactersInRange:range withString:string]; //得到输入框的内容    if ([string isEqualToString:@""]) {        return YES;    }    BOOL islength = [toBeString length] < 10;    if (!islength) {        textField.text = [toBeString substringToIndex:[toBeString length] -1];        UIAlertController *alert = [UIAlertController alertControllerWithTitle:@"⚠️警告" message:@"用户名和密码不能超过10个字符！" preferredStyle:UIAlertControllerStyleAlert];        [alert addAction:[UIAlertAction actionWithTitle:@"确定" style:UIAlertActionStyleDefault handler:^(UIAlertAction * _Nonnull action) {                    }]];        [self presentViewController:alert animated:YES completion:nil];            }        return canChange && islength;}

3.return 按键对应的协议方法

#pragma UITextFieldDelegate-(BOOL)textFieldShouldReturn:(UITextField *)textField {    [textField resignFirstResponder];//放弃第一响应者，收起键盘    textField.text = @"";  //将文本内容置空    return YES;}

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