UITextView相关设置整理

/**
UITextView:
1.能显示任意行文字
2.不能设置占位文字
3.继承自UIScollView
4.监听行为
1> 设置代理
2> 通知:UITextViewTextDidChangeNotification

UITextField:
1.文字永远是一行，不能显示多行文字
2.有placehoder属性设置占位文字
3.继承自UIControl
4.监听行为
1> 设置代理
2> addTarget:action:forControlEvents:
3> 通知:UITextFieldTextDidChangeNotification
*/

主要步骤：
1.先自定义一个QTXTextView,便于自己的文本输入使用：

//  增强版自定义TextView：带有占位文字
#import <UIKit/UIKit.h>

@interface QTXTextView : UITextView
/** 占位文字 */
@property (nonatomic, copy) NSString *placeholder;
/** 占位文字的颜色 */
@property (nonatomic, strong) UIColor *placeholderColor;
@end

#import "QTXTextView.h"

@implementation QTXTextView

- (instancetype)initWithFrame:(CGRect)frame {
    
    self = [super initWithFrame:frame];
    
    if (self) {
        // 不要设置自己的delegate为自己,在外部可能随时被别人覆盖掉
//        self.delegate = self;
    
        // 修改内部文字的上下左右间隔
        self.textContainerInset = UIEdgeInsetsMake(15, 15, 15, 15);
        
        // 通知
        // 当UITextView的文字发生改变时，UITextView自己会发出一个UITextViewTextDidChangeNotification通知
        [QTXNotificationCenter addObserver:self selector:@selector(textDidChange) name:UITextViewTextDidChangeNotification object:self];
        
        
        // textview 改变字体的行间距
        NSMutableParagraphStyle *paragraphStyle = [[NSMutableParagraphStyle alloc] init];
        // 字体的行间距
        paragraphStyle.lineSpacing = 10;
        NSDictionary *attributes = @{
                                     NSFontAttributeName:[UIFont systemFontOfSize:14],
                                     NSParagraphStyleAttributeName:paragraphStyle
                                     };
        // 文字相关设置
        self.attributedText = [[NSAttributedString alloc] initWithString:@"" attributes:attributes];
        self.textColor = setupTextLabelColor;
        self.font = [UIFont systemFontOfSize:14];
    }
    return self;
}

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

/**
 *  监听文字改变
 */
- (void)textDidChange {
    
    // 重绘（重新调用）
    [self  setNeedsDisplay];
}

- (void)setPlaceholder:(NSString *)placeholder {
    _placeholder = [placeholder copy];
    
    [self setNeedsDisplay];
}

- (void)setPlaceholderColor:(UIColor *)placeholderColor {
    _placeholderColor = placeholderColor;
    
    [self setNeedsDisplay];
}

- (void)setText:(NSString *)text {
    [super setText:text];
    
    // setNeedsDisplay会在下一个消息循环时刻，调用drawRect:
    [self setNeedsDisplay];
}

- (void)setAttributedText:(NSAttributedString *)attributedText {
    
    [super setAttributedText:attributedText];
    
    [self setNeedsDisplay];
}

- (void)setFont:(UIFont *)font {
    [super setFont:font];
    
    [self setNeedsDisplay];
}

- (void)drawRect:(CGRect)rect {
    
    // 如果有输入文字，就直接返回，不画占位文字
    if (self.hasText) return;
    
    // 文字属性
    NSMutableDictionary *attrs = [NSMutableDictionary dictionary];
    attrs[NSFontAttributeName] = self.font;
    attrs[NSForegroundColorAttributeName] = self.placeholderColor ? self.placeholderColor : setupTextLabelColor;
    // 画文字
    CGFloat x = 15;
    CGFloat w = rect.size.width - 2 * x;
    CGFloat y = 15;
    CGFloat h = rect.size.height - 2 * y;
    CGRect placeholderRect = CGRectMake(x, y, w, h);
    [self.placeholder drawInRect:placeholderRect withAttributes:attrs];
}
@end

2.在所需要使用的控制器里添加控件及代理

<UITextViewDelegate>
// 评价输入框
@property (nonatomic, weak) QTXTextView *commentTextView;

// 设置评价输入框
    QTXTextView *commentTextView = [[QTXTextView alloc]initWithFrame:CGRectMake(0, CGRectGetMaxY(line2.frame), UI_View_Width, 150)];
    commentTextView.backgroundColor = [UIColor whiteColor];
    commentTextView.delegate = self;
    commentTextView.placeholder = @" 请留下您的宝贵意见，建议1~200字";
    [self.bgView addSubview:commentTextView];
    self.commentTextView = commentTextView;

#pragma mark- UITextViewDelegate

// 限制字数
- (BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text {
    
    if (range.location >= 200) {
        
        return NO;
    } else if ([text isEqualToString:@"\n"]) { // 点击return收起键盘
        
        [textView resignFirstResponder];
        return NO;
    }
    
    return YES;
}