动态改变textview的高度

- (float) QiuTanTiYuHeightForTextView: (UITextView *)textView QiuTanTiYuWithText: (NSString *) strText{
    CGSize constraint = CGSizeMake(textView.contentSize.width , CGFLOAT_MAX);
    CGRect size = [strText boundingRectWithSize:constraint
                                        options:(NSStringDrawingUsesLineFragmentOrigin|NSStringDrawingUsesFontLeading)
                                     attributes:@{NSFontAttributeName: TYZXFANGSCMEDIUM(14)}
                                        context:nil];
    float textHeight = size.size.height + 22.0;
    return textHeight;
}

-(BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text{
    CGRect QiuTanTiYuFrame = textView.frame;
    float QiuTanTiYuHeight = [self QiuTanTiYuHeightForTextView:textView QiuTanTiYuWithText:textView.text];
    QiuTanTiYuFrame.size.height = QiuTanTiYuHeight;
    [UIView animateWithDuration:0.5 animations:^{
        textView.frame = QiuTanTiYuFrame;
    }];
    [self.QiuTanTiYuTextView mas_updateConstraints:^(MASConstraintMaker *make) {
        make.height.mas_equalTo(QiuTanTiYuHeight);
    }];

    return YES;
}

-(void)textViewDidChange:(UITextView *)textView{
    if (textView.text.length>0) {
        self.QiuTanTiYuPlaceHolderLabel.hidden = YES;
    }else{
        self.QiuTanTiYuPlaceHolderLabel.hidden = NO;
    }
}