奋斗的七月

*******夜深了，直接上代码*******

用法如下

    _inputView = [[CMInputView alloc]initWithFrame:CGRectMake(50, 100, 300, 40)];

    _inputView.font = [UIFont systemFontOfSize:18];
    _inputView.placeholder = @"测试文字";
    _inputView.cornerRadius = 4;
    _inputView.placeholderColor = [UIColor redColor];
    //_inputView.placeholderFont = [UIFont systemFontOfSize:22];
    _inputView.backgroundColor =[UIColor greenColor];
    [_inputView textValueDidChanged:^(NSString *text, CGFloat textHeight) {
        CGRect frame = _inputView.frame;
        frame.size.height = textHeight;
        _inputView.frame = frame;
    }];
    // 设置文本框最大行数
    _inputView.maxNumberOfLines = 4;
    [self.view addSubview:_inputView];

CMInputView.h

//
//  CMInputView
//

#import <UIKit/UIKit.h>

typedef void(^CM_textHeightChangedBlock)(NSString *text,CGFloat textHeight);


@interface CMInputView : UITextView

/**
 *  占位文字
 */
@property (nonatomic, strong) NSString *placeholder;

/**
 *  占位文字颜色
 */
@property (nonatomic, strong) UIColor *placeholderColor;

/**
 *  占位符字体大小
 */
@property (nonatomic,strong) UIFont *placeholderFont;

/**
 *  textView最大行数
 */
@property (nonatomic, assign) NSUInteger maxNumberOfLines;

/**
 *  文字高度改变block → 文字高度改变会自动调用
 *  block参数(text) → 文字内容
 *  block参数(textHeight) → 文字高度
 */
@property (nonatomic, strong) CM_textHeightChangedBlock textChangedBlock;
/**
 *  设置圆角
 */
@property (nonatomic, assign) NSUInteger cornerRadius;

- (void)textValueDidChanged:(CM_textHeightChangedBlock)block;


@end

CMInputView.m

//
//  CMInputView
//

#import "CMInputView.h"

@interface CMInputView ()
/**
 *  UITextView作为placeholderView，使placeholderView等于UITextView的大小，字体重叠显示，方便快捷，解决占位符问题.
 */
@property (nonatomic, weak) UITextView *placeholderView;

/**
 *  文字高度
 */
@property (nonatomic, assign) NSInteger textH;

/**
 *  文字最大高度
 */
@property (nonatomic, assign) NSInteger maxTextH;


@end

@implementation CMInputView

- (void)textValueDidChanged:(CM_textHeightChangedBlock)block{
    
    _textChangedBlock = block;

}
- (UITextView *)placeholderView
{
    if (!_placeholderView ) {
        UITextView *placeholderView = [[UITextView alloc] initWithFrame:self.bounds];
        _placeholderView = placeholderView;
        //防止textView输入时跳动问题
        _placeholderView.scrollEnabled = NO;
        _placeholderView.showsHorizontalScrollIndicator = NO;
        _placeholderView.showsVerticalScrollIndicator = NO;
        _placeholderView.userInteractionEnabled = NO;
        _placeholderView.font =  self.font;
        _placeholderView.textColor = [UIColor lightGrayColor];
        _placeholderView.backgroundColor = [UIColor clearColor];
        [self addSubview:placeholderView];
    }
    return _placeholderView;
}

- (void)setMaxNumberOfLines:(NSUInteger)maxNumberOfLines
{
    _maxNumberOfLines = maxNumberOfLines;
    
    /**
     *  根据最大的行数计算textView的最大高度
     *  计算最大高度 = (每行高度 * 总行数 + 文字上下间距)
     */
    _maxTextH = ceil(self.font.lineHeight * maxNumberOfLines + self.textContainerInset.top + self.textContainerInset.bottom);
}

- (void)setCornerRadius:(NSUInteger)cornerRadius
{
    _cornerRadius = cornerRadius;
    self.layer.cornerRadius = cornerRadius;
}

/**
 *  通过设置placeholder设置私有属性placeholderView中的textColor
 */
- (void)setPlaceholderColor:(UIColor *)placeholderColor
{
    _placeholderColor = placeholderColor;
    
    self.placeholderView.textColor = placeholderColor;
}
/**
 *  通过设置placeholder设置私有属性placeholderView中的textColor
 */
- (void)setPlaceholder:(NSString *)placeholder
{
    _placeholder = placeholder;
    
    self.placeholderView.text = placeholder;
}
/**
 *  通过设置_placeholderFont设置私有属性placeholderView中的Font
*/
- (void)setPlaceholderFont:(UIFont *)placeholderFont {

    _placeholderFont = placeholderFont;
    
    self.placeholderView.font = placeholderFont;
}


- (instancetype)initWithFrame:(CGRect)frame
{
    if (self = [super initWithFrame:frame]) {
        
        [self setup];
    }
    return self;
}

- (void)setup
{
    
    self.scrollEnabled = NO;
    self.scrollsToTop = NO;
    self.showsHorizontalScrollIndicator = NO;
    self.enablesReturnKeyAutomatically = YES;
    self.layer.borderWidth = 1;
    self.layer.borderColor = [UIColor lightGrayColor].CGColor;
    //实时监听textView值得改变
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(textDidChange) name:UITextViewTextDidChangeNotification object:self];
}

- (void)textDidChange
{
    // 根据文字内容决定placeholderView是否隐藏
    self.placeholderView.hidden = self.text.length > 0;
    
    NSInteger height = ceilf([self sizeThatFits:CGSizeMake(self.bounds.size.width, MAXFLOAT)].height);
    
    if (_textH != height) { // 高度不一样，就改变了高度
        
        // 当高度大于最大高度时，需要滚动
        self.scrollEnabled = height > _maxTextH && _maxTextH > 0;
        
        _textH = height;
        
        //当不可以滚动（即 <= 最大高度）时，传值改变textView高度
        if (_textChangedBlock && self.scrollEnabled == NO) {
            _textChangedBlock(self.text,height);
            
            [self.superview layoutIfNeeded];
            self.placeholderView.frame = self.bounds;

        }
    }
}


- (void)dealloc
{
    [[NSNotificationCenter defaultCenter] removeObserver:self];
}

@end