UITextField 的使用

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

//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;
}

#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;
}