UITextField最大字符數和最大字節數的限制

2334471588 8年前發布 | 10K 次閱讀 iOS開發移動開發 UITextField

UITextView , UITextfield 中有很多坑，網上的方法也很多。但是并不是很全面吧，這里全面進行了總結，并進行了封裝。歡迎大家下載。

一. 字符限制

1. 錯誤方法

常見的這種方法是錯誤的，會導致Emoj表情的截取問題

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
    if(range.length + range.location > textField.text.length)
    {
        return NO;
    }

    NSUInteger newLength = [textField.text length] + [string length] - range.length;
    return newLength <= 5;
}

這種限制方法會導致拼音下出現這種情況，且無法輸入.無法輸入滿5個字符。在emoj表情也有問題

2. 推薦方法

使用rangeOfComposedCharacterSequencesForRange, 防止在range范圍內整詞被截斷

- (void)textFieldDidChange:(UITextField *)textField
{
    NSString *toBeString = textField.text;

    UITextRange *selectedRange = [textField markedTextRange];
    UITextPosition *position = [textField positionFromPosition:selectedRange.start offset:0];

    // 沒有高亮選擇的字，則對已輸入的文字進行字數統計和限制,防止中文被截斷
    if (!position){
        if (toBeString.length > _maxLength){
            //中文和emoj表情存在問題，需要對此進行處理
            NSRange rangeRange = [toBeString rangeOfComposedCharacterSequencesForRange:NSMakeRange(0, _maxLength)];
            textField.text = [toBeString substringWithRange:rangeRange];
        }
    }
}

二. 字節限制

1. 限制字節數

在UTF8中，英文和數字是1個字節,漢子是3個字節，emoji是3或者4個字節。這里的難度比上面更大，如果截取失敗，極有可能出現亂碼。這里我們的做法如下

- (void)textFieldDidChange:(UITextField *)textField
{
    NSString *toBeString = textField.text;
    //---字節處理
    NSInteger bytesCount = strlen([textField.text UTF8String]);
    if (bytesCount > _maxBytesLength) {
      NSString *content = [textField.text subStrWithUtf8Len:(int)_maxBytesLength];
      textField.text = content;
    }
}

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string{

    NSString * inputString = [textField.text stringByReplacingCharactersInRange:range withString:string];

    //限制字節數
    if ([inputString length] > 0){
        NSInteger len = strlen([inputString UTF8String]);
        if (len > _maxBytesLength){
            return NO;
        }
        else {
            return  YES;
        }
    }
   return YES;
}

這里不能只在進行限制，在textFieldDidChange中需要對中文聯想做處理才行

三. 放棄鍵盤

1. 能拿到uitextfield的時候用

- (BOOL)textFieldShouldReturn:(UITextField *)textField
{
    return [textField resignFirstResponder];
}

2. 點擊view消失的時候用

[self.view endEditing:YES];

3. 難以獲取的時候用

[[UIApplication sharedApplication] sendAction:@selector(resignFirstResponder) to:nil from:nil forEvent:nil];

或者

[[[UIApplication sharedApplication] keyWindow] endEditing:YES];

2.Tableview點擊空白處或者滾動時消失

{
    UITapGestureRecognizer *singleTap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(fingerTapped:)];
    [self.view addGestureRecognizer:singleTap];
}

#pragma mark- 鍵盤消失
-(void)fingerTapped:(UITapGestureRecognizer *)gestureRecognizer{
    [self.view endEditing:YES];
}
-(void)scrollViewWillBeginDragging:(UIScrollView *)scrollView{
    [self.view endEditing:YES];
}

四. 正則表達式限制

請參考正則表達式語法表 ,這里我提供了兩種表達式給大家參考，一個Int,一個無unsignedInt

-(BOOL) isTextFieldMatchWithRegularExpression:(NSString *)exporession{

    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"SELF MATCHES %@",exporession];
    return [predicate evaluateWithObject:self];
}
-(BOOL) isTextFieldIntValue{
    return [self isTextFieldMatchWithRegularExpression:@"[-]{0,1}[0-9]*"];
}
-(BOOL) isTextFieldUnsignedIntValue{
    return [self isTextFieldMatchWithRegularExpression:@"[0-9]+"];
}

五. UITextfield的鍵盤事件多次回調問題

1.鍵盤高度遮擋問題

一般出現遮擋的時候我們用以下代碼,看看當前textfield是否在鍵盤下面，在的話算出鍵盤的頂端和textfield的底部的距離，然后做偏移動畫

- (void)keyboardWillShow:(NSNotification *)notification {

    NSDictionary *userInfo = [notification userInfo];

    NSValue* aValue = [userInfo objectForKey:UIKeyboardFrameEndUserInfoKey];
    CGRect keyboardRect = [aValue CGRectValue];
    keyboardRect = [self.view convertRect:keyboardRect fromView:nil];

    CGFloat keyboardTop = keyboardRect.origin.y;

    CGFloat offset = self.normalTextField.frame.size.height + self.normalTextField.frame.origin.y - keyboardTop;

    NSValue *animationDurationValue = [userInfo objectForKey:UIKeyboardAnimationDurationUserInfoKey];
    NSTimeInterval animationDuration;
    [animationDurationValue getValue:&animationDuration];

    if(offset > 0){
        // Animate the resize of the text view's frame in sync with the keyboard's appearance.
        [UIView beginAnimations:nil context:NULL];
        [UIView setAnimationDuration:animationDuration];

        CGRect rect = CGRectMake(0.0f, -offset,self.view.frame.size.width,self.view.frame.size.height);
        self.view.frame = rect;
        [UIView commitAnimations];
    }
}

真機

如果使用了中文輸入法，注冊的keyboardWillShow會回調兩次。第一次是鍵盤默認高度216，第二次則是加了keyboard的導航欄的高度。
模擬器

第一次彈出鍵盤沒有問題

打印userinfo:

(lldb) po userInfo
{
    UIKeyboardAnimationCurveUserInfoKey = 7;
    UIKeyboardAnimationDurationUserInfoKey = "0.25";
    UIKeyboardBoundsUserInfoKey = "NSRect: {{0, 0}, {414, 226}}";
    UIKeyboardCenterBeginUserInfoKey = "NSPoint: {207, 849}";
    UIKeyboardCenterEndUserInfoKey = "NSPoint: {207, 623}";
    UIKeyboardFrameBeginUserInfoKey = "NSRect: {{0, 736}, {414, 226}}";
    UIKeyboardFrameEndUserInfoKey = "NSRect: {{0, 510}, {414, 226}}";
    UIKeyboardIsLocalUserInfoKey = 1;
}

此時我們去按123旁邊的小圓球會出現如下的圖：

打印userinfo:

(lldb) po userInfo
{
    UIKeyboardAnimationCurveUserInfoKey = 7;
    UIKeyboardAnimationDurationUserInfoKey = "0.25";
    UIKeyboardBoundsUserInfoKey = "NSRect: {{0, 0}, {414, 271}}";
    UIKeyboardCenterBeginUserInfoKey = "NSPoint: {207, 623}";
    UIKeyboardCenterEndUserInfoKey = "NSPoint: {207, 600.5}";
    UIKeyboardFrameBeginUserInfoKey = "NSRect: {{0, 510}, {414, 226}}";
    UIKeyboardFrameEndUserInfoKey = "NSRect: {{0, 465}, {414, 271}}";
    UIKeyboardIsLocalUserInfoKey = 1;
}

鍵盤被遮擋了。

總結:觀察結果,發現了這個規律，打印一下時間,還有一個問題就是，中文鍵盤第一次啟動的時候會回調兩次。

keyboardRect = [self.view convertRect:keyboardRect fromView:nil];

所以去掉這句話即可

六. 使用封裝的XXTextField

UITextView , UITextfield 中如果有keyboard的時候，需要一個自動彈起事件，以及彈起之后的content的偏移對父view的處理。如果每個頁面都實現一次會非常復雜。這里我們介紹一種自動化的處理機制。在此之前，先介紹一下文字處理框架.最后給大家推薦一下我寫的 XXTextField ,大家也可以在此基礎上自己添加一些正則表達式。使用方法很簡單.歡迎加入QQ群：237305299 ，一起探討iOS技術問題

1.解決uiview中的textfield 遮擋問題

_textfieldName.keyboardType = UIKeyboardTypeDefault;
_textfieldName.inputType = XXTextFieldTypeOnlyInt;
_textfieldName.maxLength = 5;
_textfieldPwd.inputType = XXTextFieldTypeForbidEmoj;

#import "XXKeyboardManager.h"
@interface XXCorrectVC ()<XXKeyboardManagerShowHiddenNotificationDelegate>
@end

@implementation XXCorrectVC

- (void)viewDidLoad {
    [super viewDidLoad];
    [[XXKeyboardManager sharedInstance] setDelegate:self];
    // Do any additional setup after loading the view from its nib.
}
#pragma mark- KeyBoardShow/Hidden
- (void)showKeyboardWithRect:(CGRect)keyboardRect
                withDuration:(CGFloat)animationDuration
{
    CGFloat offset = self.textFieldCorrect.frame.size.height + self.textFieldCorrect.frame.origin.y - keyboardRect.origin.y;
    if(offset < 0){
        return;
    }
    [UIView animateWithDuration:animationDuration
                          delay:0.f
                        options:UIViewAnimationOptionCurveEaseInOut animations:^{
        CGRect rect = CGRectMake(0.0f, -offset,self.view.frame.size.width,self.view.frame.size.height);
        self.view.frame = rect;
    } completion:^(BOOL finished) {

    }];
}

- (void)hiddenKeyboardWithRect:(CGRect)keyboardRect
                  withDuration:(CGFloat)animationDuration
{
    [UIView animateWithDuration:animationDuration
                          delay:0.f
                        options:UIViewAnimationOptionCurveEaseInOut animations:^{
        self.textFieldCorrect.frame = self.view.bounds;
    } completion:^(BOOL finished) {
    }];
}
@end

2.解決uitableview中鍵盤遮擋問題

/*
 * 鍵盤要顯示的時候
 */
- (void)showKeyboardWithRect:(CGRect)keyboardRect
                withDuration:(CGFloat)animationDuration{

    CGSize kbSize = keyboardRect.size;

    UIEdgeInsets contentInsets = UIEdgeInsetsMake(0.0, 0.0, kbSize.height, 0.0);
    _baseTableView.contentInset = contentInsets;
    _baseTableView.scrollIndicatorInsets = contentInsets;

    // If active text field is hidden by keyboard, scroll it so it's visible
    // Your app might not need or want this behavior.
    CGRect aRect = self.view.frame;
    aRect.size.height -= kbSize.height;

    if (!CGRectContainsPoint(aRect, _activeCell.frame.origin) ) {
        [_baseTableView scrollRectToVisible:_activeCell.frame animated:YES];
    }
}

/*
 * 鍵盤要消失的時候
 */
- (void)hiddenKeyboardWithRect:(CGRect)keyboardRect
                  withDuration:(CGFloat)animationDuration{
    _baseTableView.contentInset = UIEdgeInsetsZero;
    _baseTableView.scrollIndicatorInsets = UIEdgeInsetsZero;
}

來自：http://www.iosxxx.com/blog/2016-11-27-UITextField最大字符數和最大字節數的限制.html

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iOS開發移動開發 UITextField