UITextView 输入字数限制

- (BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range
replacementText:(NSString *)text; - (void)textViewDidChange:(UITextView *)textView;

#define MAX_LIMIT_NUMS 100 //最大限制字数

- (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:];
//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 < MAX_LIMIT_NUMS) {
return YES;
}
else
{
return NO;
}
} NSString *comcatstr = [textView.text stringByReplacingCharactersInRange:range withString:text]; NSInteger caninputlen = MAX_LIMIT_NUMS - comcatstr.length; if (caninputlen >= )
{
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 = {,MAX(len,)}; if (rg.length > )
{
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 = ;
__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(, [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]];
}
return NO;
}
}

-(void)textViewDidChange:(UITextView *)textView
{
UITextRange *selectedRange = [textView markedTextRange];
//获取高亮部分
UITextPosition *pos = [textView positionFromPosition:selectedRange.start offset:];
//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 > MAX_LIMIT_NUMS)
{
//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:MAX_LIMIT_NUMS]; [textView setText:s];
} }