本文讨论了在文本输入场景中，当输入字符长度超过预设限制时，如何处理高亮显示的拼音字符串，包括候选词替换、高亮拼音截取与删除情况下的文本长度计算与限制。
- (BOOL) textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
NSInteger textLength = 0;
UITextRange *selectedRange = [textField markedTextRange]; //获取高亮部分
UITextPosition *position = [textField positionFromPosition:selectedRange.start offset:0];
if (!position) {
textLength = [Utils getStringAsciiLength:textField.text];
}
if (string.length > 0) { //输入状态
if (textField.text.length > range.location) { //候选词替换高亮拼音时
NSString *newStr = [NSString stringWithFormat:@"%@%@",[textField.text substringToIndex:range.location],
string];
textLength = [Utils getStringAsciiLength:newStr];
}else {
textLength += [Utils getStringAsciiLength:string];
}
}else { //删除状态
if (textField.text.length > 0) {
textLength = [Utils getStringAsciiLength:[textField.text substringToIndex:range.location]];
}
}
if (textLength > maxStrLength) { //如果输入的字符长度超过限制长度，则进行截取
if (textField.text.length >= range.location) {
textField.text = [NSString stringWithFormat:@"%@%@",[textField.text substringToIndex:range.location],string];
}
textField.text = [Utils subStringByAsciiLength:textField.text withLength:maxStrLength];
return NO;
}
return YES;
}
PS:Utils类的getStringAsciiLength:(NSString *)str方法根据字符串的编码或者字符串占用字符数
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