主要是通过两个代理方法过来实现
- (BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range
replacementText:(NSString *)text{
UITextRange *selectedRange = [textView markedTextRange];
//获取高亮部分
UITextPosition *pos = [textView positionFromPosition:selectedRange.start offset:0];
//获取高亮部分内容
//NSString * selectedtext = [textView textInRange:selectedRange];
//如果有高亮且当前字数开始位置小于最大限制时允许输入
if (selectedRange && pos) {
NSInteger startOffset = [textView offsetFromPosition:textView.beginningOfDocument toPosition:selectedRange.start];
NSInteger endOffset = [textView offsetFromPosition:textView.beginningOfDocument toPosition:selectedRange.end];
NSRange offsetRange = NSMakeRange(startOffset, endOffset - startOffset);
if (offsetRange.location < self.feedBackView.maxStr) {
return YES;
}else{
return NO;
}
}
NSString *comcatstr = [textView.text stringByReplacingCharactersInRange:range withString:text];
NSInteger caninputlen = self.feedBackView.maxStr - comcatstr.length;
if (caninputlen >= 0){
return YES;
}else{
NSInteger len = text.length + caninputlen;
//防止当text.length + caninputlen < 0时，使得rg.length为一个非法最大正数出错
NSRange rg = {0,MAX(len,0)};
if (rg.length > 0){
NSString *s = @"";
//判断是否只普通的字符或asc码(对于中文和表情返回NO)
BOOL asc = [text canBeConvertedToEncoding:NSASCIIStringEncoding];
if (asc) {
s = [text substringWithRange:rg];//因为是ascii码直接取就可以了不会错
}else{
__block NSInteger idx = 0;
__block NSString *trimString = @"";//截取出的字串
//使用字符串遍历，这个方法能准确知道每个emoji是占一个unicode还是两个
[text enumerateSubstringsInRange:NSMakeRange(0, [text length])
options:NSStringEnumerationByComposedCharacterSequences
usingBlock: ^(NSString* substring, NSRange substringRange, NSRange enclosingRange, BOOL* stop) {
if (idx >= rg.length) {
*stop = YES; //取出所需要就break，提高效率
return ;
}
trimString = [trimString stringByAppendingString:substring];
idx++;
}];
s = trimString;
}
//rang是指从当前光标处进行替换处理(注意如果执行此句后面返回的是YES会触发didchange事件)
[textView setText:[textView.text stringByReplacingCharactersInRange:range withString:s]];
//既然是超出部分截取了，哪一定是最大限制了。
self.feedBackView.lblMax.text = [NSString stringWithFormat:@"%d/%ld字",0,(long)self.feedBackView.maxStr];
}
return NO;
}
}
- (void)textViewDidChange:(UITextView *)textView{
UITextRange *selectedRange = [textView markedTextRange];
//获取高亮部分
UITextPosition *pos = [textView positionFromPosition:selectedRange.start offset:0];
//如果在变化中是高亮部分在变，就不要计算字符了
if (selectedRange && pos) {
return;
}
NSString *nsTextContent = textView.text;
NSInteger existTextNum = nsTextContent.length;
if (existTextNum > self.feedBackView.maxStr){
//截取到最大位置的字符(由于超出截部分在should时被处理了所在这里这了提高效率不再判断)
NSString *s = [nsTextContent substringToIndex:self.feedBackView.maxStr];
[textView setText:s];
}
//不让显示负数 口口日
self.feedBackView.lblMax.text = [NSString stringWithFormat:@"%ld/%ld字",MAX(0,self.feedBackView.maxStr - existTextNum),self.feedBackView.maxStr];
}