工欲善其事，必先利其器系列之 UITextView+Catego

UITextView 也是较长用的控件之一，唯一问题就是没有占位符
本文介绍：
1、UITextView 添加占位符
2、算textview输入情况下的字符数，解决实现限制字符数时，计算不准的问题

直接上代码：

UITextView+Category.h

#import <UIKit/UIKit.h>
#import <objc/runtime.h>

@interface UITextView (Category)<UITextViewDelegate>

@property (nonatomic, strong) UITextView *placeHolderTextView;
/**
 *  @brief  占位符
 */
- (void)add_PlaceHolder:(NSString *)placeHolder;

/**
 *  @brief  当前选中的字符串范围
 *
 *  @return NSRange
 */
- (NSRange)selectedRange;
/**
 *  @brief  选中所有文字
 */
- (void)selectAllText;
/**
 *  @brief  选中指定范围的文字
 *
 *  @param range NSRange范围
 */
- (void)setSelectedRange:(NSRange)range;

// 用于计算textview输入情况下的字符数，解决实现限制字符数时，计算不准的问题
- (NSInteger)getInputLengthWithText:(NSString *)text;

UITextView+Category.m

#import "UITextView+Category.h"

static const char *phTextView = "placeHolderTextView";

@implementation UITextView (Category)

/**
 *  @brief  占位符
 */
- (UITextView *)placeHolderTextView {
    return objc_getAssociatedObject(self, phTextView);
}
- (void)setPlaceHolderTextView:(UITextView *)placeHolderTextView {
    objc_setAssociatedObject(self, phTextView, placeHolderTextView, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}
- (void)add_PlaceHolder:(NSString *)placeHolder {
    if (![self placeHolderTextView]) {
        self.delegate = self;
        UITextView *textView = [[UITextView alloc] initWithFrame:self.bounds];
        textView.autoresizingMask = UIViewAutoresizingFlexibleHeight | UIViewAutoresizingFlexibleWidth;
        textView.font = self.font;
        textView.backgroundColor = [UIColor clearColor];
        textView.textColor = [UIColor grayColor];
        textView.userInteractionEnabled = NO;
        textView.text = placeHolder;
        [self addSubview:textView];
        [self setPlaceHolderTextView:textView];
    }
}
# pragma mark -
# pragma mark - UITextViewDelegate
- (void)textViewDidBeginEditing:(UITextView *)textView {
    self.placeHolderTextView.hidden = YES;
    // if (self.textViewDelegate) {
    //
    // }
}
- (void)textViewDidEndEditing:(UITextView *)textView {
    if (textView.text && [textView.text isEqualToString:@""]) {
        self.placeHolderTextView.hidden = NO;
    }
}

- (BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text
{
    NSInteger textLength = [textView getInputLengthWithText:text];
    if (textLength > 20) {
        // 超过20个字可以删除
        if ([text isEqualToString:@""]) {
            return YES;
        }
        return NO;
    }
    return YES;
}

- (void)textViewDidChange:(UITextView *)textView
{
    if ([textView getInputLengthWithText:nil] > 20) {
        textView.text = [textView.text substringToIndex:20];
    }
}


/**
 *  @brief  当前选中的字符串范围
 *
 *  @return NSRange
 */
- (NSRange)selectedRange
{
    UITextPosition* beginning = self.beginningOfDocument;
    
    UITextRange* selectedRange = self.selectedTextRange;
    UITextPosition* selectionStart = selectedRange.start;
    UITextPosition* selectionEnd = selectedRange.end;
    
    NSInteger location = [self offsetFromPosition:beginning toPosition:selectionStart];
    NSInteger length = [self offsetFromPosition:selectionStart toPosition:selectionEnd];
    
    return NSMakeRange(location, length);
}
/**
 *  @brief  选中所有文字
 */
- (void)selectAllText {
    UITextRange *range = [self textRangeFromPosition:self.beginningOfDocument toPosition:self.endOfDocument];
    [self setSelectedTextRange:range];
}
/**
 *  @brief  选中指定范围的文字
 *
 *  @param range NSRange范围
 */
- (void)setSelectedRange:(NSRange)range {
    UITextPosition *beginning = self.beginningOfDocument;
    UITextPosition *startPosition = [self positionFromPosition:beginning offset:range.location];
    UITextPosition *endPosition = [self positionFromPosition:beginning offset:NSMaxRange(range)];
    UITextRange *selectionRange = [self textRangeFromPosition:startPosition toPosition:endPosition];
    [self setSelectedTextRange:selectionRange];
}
//https://github.com/pclion/TextViewCalculateLength
// 用于计算textview输入情况下的字符数，解决实现限制字符数时，计算不准的问题

- (NSInteger)getInputLengthWithText:(NSString *)text
{
    NSInteger textLength = 0;
    //获取高亮部分
    UITextRange *selectedRange = [self markedTextRange];
    if (selectedRange) {
        NSString *newText = [self textInRange:selectedRange];
        textLength = (newText.length + 1) / 2 + [self offsetFromPosition:self.beginningOfDocument toPosition:selectedRange.start] + text.length;
    } else {
        textLength = self.text.length + text.length;
    }
    return textLength;
}

@end

用法

    UITextView * textView =[[UITextView alloc]initWithFrame:CGRectMake(30, 100, KScreenWidth-60, 250)];
    textView.backgroundColor = [UIColor lightGrayColor];
    textView.font = [UIFont systemFontOfSize:18];
    [textView add_PlaceHolder:@"请输入内心独白（20字以内）~"];
    [self.view addSubview:textView];

效果

9E07218F-AB43-414E-9304-523644A4F575.png

项目传送门
项目地址
https://github.com/SmileMee/SmileHelper.git

---

我是写代码的凡，如有错误，欢迎指正！🙂🙂🙂