记录一次YYTextView如何实现限制字数

2018-8-26.jpeg

前言

源于项目重构，需要剔除无用的资源文件和减少第三方库的使用。在检查工程文件的时候发现UITextView-Placeholder有点多余( 注:YYText已经存在).就想着用YYTextView来实现编辑签名。

YYTextView

创建视图

-(void)addOwnView{
    self.textView = [YYTextView  new];
    self.textView.placeholderText = @"请输入内容";
    self.textView.placeholderFont = [UIFont systemFontOfSize:14];
    [self.textView setBackgroundColor:[UIColor whiteColor]];
    self.textView.font            = [UIFont systemFontOfSize:14];
    self.textView.contentSize     = CGSizeMake(self.view.width, 200);
    self.textView.contentInset    = UIEdgeInsetsMake(0, 10, 0, 10);
    self.textView.frame = CGRectMake(0, 0, self.view.width, 200);
    [self.view addSubview:self.textView];
}

添加监听事件

-(void)addObserver{
    
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(textViewDidChangeNotification:) name:YYTextViewTextDidChangeNotification object:self.textView];
}
#pragma mark 关键方法  
#pragma mark 方法来源   https://www.jianshu.com/p/2d1c06f2dfa4
-(void)textViewDidChangeNotification:(NSNotification*)obj{
   
    YYTextView *textView = (YYTextView *)obj.object;
    NSString *toBeString = textView.text;
    
    //获取高亮部分
    UITextRange *selectedRange = [textView markedTextRange];
    UITextPosition *position = [textView positionFromPosition:selectedRange.start offset:0];
    // 没有高亮选择的字，则对已输入的文字进行字数统计和限制
    if (!position)
    {
        if (toBeString.length > MAX_STARWORDS_LENGTH)
        {
            NSRange rangeIndex = [toBeString rangeOfComposedCharacterSequenceAtIndex:MAX_STARWORDS_LENGTH];
            if (rangeIndex.length == 1)
            {
                textView.text = [toBeString substringToIndex:MAX_STARWORDS_LENGTH];
            }
            else
            {
                NSRange rangeRange = [toBeString rangeOfComposedCharacterSequencesForRange:NSMakeRange(0, MAX_STARWORDS_LENGTH)];
                textView.text = [toBeString substringWithRange:rangeRange];
            }
        }
    }
}

YYTextView监听方法校验修改

经过测试发现上面的方法根本行不通，测试才知道下面的selectedRange获取到值为空，想着如何才能获取selectedRange值的问题去看了一下源码。源码显示_markedTextRange是存在的,但是读取时却为空.想着用KVC获取一下试试，测试后发现完全可以。

  UITextRange *selectedRange = [textView markedTextRange]; // 空值

    YYTextRange *_selectedTextRange; /// nonnull
    YYTextRange *_markedTextRange;

修改如下的代码为

 YYTextView *textView = (YYTextView *)obj.object;
    NSString *toBeString = textView.text;
    //获取高亮部分
    YYTextRange *selectedRange = [textView valueForKey:@"_markedTextRange"];
    SEL selName = NSSelectorFromString(@"positionFromPosition:offset:");
    YYTextPosition *position = ((YYTextPosition *(*)(id,SEL,id,int))objc_msgSend)(textView,selName,selectedRange.start,0);
    
    // 没有高亮选择的字，则对已输入的文字进行字数统计和限制
    if (!position)
    {
        if (toBeString.length > MAX_STARWORDS_LENGTH)
        {
            NSRange rangeIndex = [toBeString rangeOfComposedCharacterSequenceAtIndex:MAX_STARWORDS_LENGTH];
            if (rangeIndex.length == 1)
            {
                textView.text = [toBeString substringToIndex:MAX_STARWORDS_LENGTH];
            }
            else
            {
                NSRange rangeRange = [toBeString rangeOfComposedCharacterSequencesForRange:NSMakeRange(0, MAX_STARWORDS_LENGTH)];
                textView.text = [toBeString substringWithRange:rangeRange];
            }
        }
    }

联系

Yee: https://github.com/Mr-yuwei/iOS-Notes

感谢

小失: iOS中UITextField的字数限制