思路：
使用runtime 获取textfiled的所有属性
//获取类的所有属性
unsigned int count = 0;
Ivar *ivarList = class_copyIvarList([UITextField class], &count);
for (int i = 0; i<count; i++) {
Ivar ivar = ivarList[i];
NSLog(@"%s",ivar_getName(ivar));
}
free(ivarList);
修改文本框内的placehold字体颜色
使用runtime // 利用KVC设置它颜色,结果成功 这里有一个问题，可能会出现低版本没有该属性，你需要进行检验下。
[textField setValue:[UIColor redColor]forKeyPath:@"_placeholderLabel.textColor"]; [textField setValue: [UIFontboldSystemFontOfSize:16] forKeyPath :@"_placeholderLabel.font"];设置属性文本
NSMutableDictionary *dict = [NSMutableDictionary dictionary]; dict[NSForegroundColorAttributeName] = [UIColor redColor]; NSAttributedString *attribute = [[NSAttributedString alloc] initWithString:self.placeholder attributes:dict]; [self setAttributedPlaceholder:attribute];- 设置光标颜色
使用@property(null_resettable, nonatomic, strong) UIColor *tintColor属性textField.tintColor = UIColorFromRGBA(rgbValue,A) - 捕捉键盘的return事件
遵守UITextFieldDelegate,并设置相关代理。实现如下代理方法`objc
- (BOOL)textFieldShouldReturn:(UITextField *)textField;
// called when ‘return’ key pressed. return NO to ignore.`
- 捕捉文本改变事件通知
要想获取到文本改变事件通知，需要监听一个通知UITextFieldTextDidChangeNotification`objc
[[NSNotificationCenter defaultCenter]addObserver:self selector:@selector(textFiledDidChange:) name:UITextFieldTextDidChangeNotification object:文本框对象];
> PS: 文本常用通知
```objc
UIKIT_EXTERN NSNotificationName const UITextFieldTextDidBeginEditingNotification; //输入框已经开始编辑
UIKIT_EXTERN NSNotificationName const UITextFieldTextDidEndEditingNotification; //输入框已经结束编辑
UIKIT_EXTERN NSNotificationName const UITextFieldTextDidChangeNotification; //输入框已经改变
- 限制文本字数
监听UITextFieldTextDidChangeNotification通知，并在方法里做如下操作。下面是我的一个代码片段。
#pragma mark - 文本改变通知
-(void)textFiledDidChange:(NSNotification*)textChange{
UITextField * field = (UITextField*)textChange.object;
NSString * toBeString = field.text;
UITextRange * selectedRange = [field markedTextRange];
UITextPosition* position = [field positionFromPosition:selectedRange.start offset:0];
if (!position) {
//判断文本字符数是否操作最大值
if (toBeString.length>30) {
NSRange rangeIndex = [toBeString rangeOfComposedCharacterSequenceAtIndex:30];
if (rangeIndex.length==1) {
field.text = [toBeString substringToIndex:30];
}else{
NSRange range = [toBeString rangeOfComposedCharacterSequencesForRange:NSMakeRange(0, 30)];
field.text = [toBeString substringWithRange:range];
}
}
if (toBeString.length==0) {
//没有输入文本处理
_characterNumber.text=[NSString stringWithFormat:@"%d/30",(int)field.text.length];
[_remark_textfield showUnderLine:UIColorFromRGBA(0xb4b4b4, 1)];
_remark_OK.enabled=NO;
}else{
// 有文本处理
_characterNumber.text=[NSString stringWithFormat:@"%d/30",(int)field.text.length];
[_remark_textfield showUnderLine:UIColorFromRGBA(0xe62f17, 1)];
if ([CheckInputValid CheckForNicknameWithInString:field.text]) {
_remark_OK.enabled=YES;
}else{
_remark_OK.enabled=NO;
}
}
}
}
个性化定制文本框右边的视图(
rightView)`objc// 初始化一个视图（可以是任一视图（UILabel,UIButton,…）），Ps 需要指定一个框高 ,你可以对这个视图添加你想要的事件
_characterNumber = [[UILabel alloc]initWithFrame:CGRectMake(0, 0, 50, 30)];
_characterNumber.text = @”0/30”;
_characterNumber.textAlignment = NSTextAlignmentRight;
_characterNumber.font = [UIFont systemFontOfSize:12];
_characterNumber.textColor = UIColorFromRGBA(0xb4b4b4, 1);// 设置右边视图
_remark_textfield.rightView = _characterNumber;// 设置右边视图的显示模式
_remark_textfield.rightViewMode = UITextFieldViewModeAlways;
8. 当键盘出现时，需要改变输入框的位置，要如何做？
要想实现这个，很简单，同样你需要监听`UIKeyboardDidChangeFrameNotification`这个通知。
```objc
[[NSNotificationCenter defaultCenter ]addObserver:self selector:@selector(keyBoardFrameChanged:) name:UIKeyboardDidChangeFrameNotification object:nil];
-(void)keyBoardFrameChanged:( NSNotification * )notification{
NSDictionary * userInfo = [notification userInfo];
NSValue * value = [userInfo objectForKey:UIKeyboardFrameEndUserInfoKey];
// 获取到键盘的位置
CGRect keyboardRect = [value CGRectValue];
CGFloat keyboardTop = keyboardRect.origin.y;
//进行你的想要的布局操作
}
PS：常见的键盘通知
`objc
UIKIT_EXTERN NSNotificationName const UIKeyboardWillChangeFrameNotification NS_AVAILABLE_IOS(5_0) TVOS_PROHIBITED; //键盘将要改变通知
UIKIT_EXTERN NSNotificationName const UIKeyboardDidChangeFrameNotification NS_AVAILABLE_IOS(5_0) TVOS_PROHIBITED; //键盘已经改变通知
UIKIT_EXTERN NSNotificationName const UIKeyboardWillShowNotification __TVOS_PROHIBITED; //键盘将要显示通知
UIKIT_EXTERN NSNotificationName const UIKeyboardDidShowNotification __TVOS_PROHIBITED; //键盘已经显示
UIKIT_EXTERN NSNotificationName const UIKeyboardWillHideNotification __TVOS_PROHIBITED; //键盘将要隐藏
UIKIT_EXTERN NSNotificationName const UIKeyboardDidHideNotification __TVOS_PROHIBITED; //键盘已经隐藏
9. 给文本框加上一根横线
对于这个，你可以给做一个子类，继承自UITextFiled. 重写drawRect方法如下所示
```objc
@interface TextFieldExtension : UITextField
/**
显示下划线
*/
-(void)showUnderLine:(UIColor* _Nullable)lineColor;
@end
#import "TextFieldExtension.h"
@interface TextFieldExtension ()
@property(nonatomic,assign) BOOL showunderline;
@property(nonatomic,strong)UIColor * lineColor;
@end
@implementation TextFieldExtension
- (void)drawRect:(CGRect)rect {
if (_showunderline) {
// Drawing code
CGContextRef context = UIGraphicsGetCurrentContext();
[self.lineColor set];//设置下划线颜色 这里是红色 可以自定义
CGFloat y = CGRectGetHeight(self.frame);
CGContextMoveToPoint(context, 0, y);
CGContextAddLineToPoint(context, CGRectGetWidth(self.frame), y);
//设置线的宽度
CGContextSetLineWidth(context, 1);
//渲染 显示到self上
CGContextStrokePath(context);
}
}
-(void)showUnderLine:(UIColor *)lineColor{
_showunderline=YES;
_lineColor=lineColor;
[self setNeedsDisplay];
}
-(UIColor *)lineColor{
if (!_lineColor) {
_lineColor =[UIColor grayColor];
}
return _lineColor;
}
@end
