iOS

一、使用KVC，查找textView内部变量

UITextView

1.新建UITextView的Category，命名为UITextView+PlaceHolder，.h和.m代码分别如下

#import <UIKit/UIKit.h>@interface UITextView (Placeholder)@property (nonatomic, copy) NSString *placeHolder;@end

#import "UITextView+Placeholder.h"@implementation UITextView (Placeholder)- (void)setPlaceHolder:(NSString *)placeHolder {    UILabel *placeHolderStr = [[UILabel alloc] init];    placeHolderStr.text = placeHolder;    placeHolderStr.numberOfLines = 0;    placeHolderStr.textColor = [UIColor lightGrayColor];    [placeHolderStr sizeToFit];    [self addSubview:placeHolderStr];    placeHolderStr.font = self.font;    [self setValue:placeHolderStr forKey:@"_placeholderLabel"];}@end

2.调用时引入头文件后

- (void)textViewplaceHolderMethod {    self.textView.layer.masksToBounds = YES;    self.textView.layer.cornerRadius = 4;    self.textView.layer.borderWidth = 0.5;    self.textView.layer.borderColor = [UIColor blackColor].CGColor;    self.textView.placeHolder = @"请留下您对我们的建议或意见";}

二、（笨方法）使用textView/label充当placeHolder

1.具体思路：在UITextView的delegate方法中控制

self.textView.text = @"";

或者

self.placeHolderLabel.hidden = Yes;

2.具体代码（UITextView.text）

- (void)setupTextView {    self.textView.delegate = self;    self.textView.text = @"请输入您的建议";    self.textView.textColor = [UIColor lightGrayColor];    self.textView.layer.masksToBounds = YES;    self.textView.layer.cornerRadius = 4;    self.textView.layer.borderWidth = 0.5;    self.textView.layer.borderColor = [UIColor blackColor].CGColor;}- (void)textViewDidBeginEditing:(UITextView *)textView {    if ([textView.text isEqualToString:@"请输入您的建议"]) {        self.textView.text = @"";        self.textView.textColor = [UIColor blackColor];    }}- (void)textViewDidEndEditing:(UITextView *)textView {    if (textView.text.length == 0) {        self.textView.text = @"请输入您的建议";        self.textView.textColor = [UIColor lightGrayColor];    }}- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {    [self.view endEditing:YES];}

注：这个方法的缺点是当你输入 “请输入您的建议” 后，键盘失去响应后，在点击想继续输入的时候，原输入的 “请输入您的建议” 会消失，所以比较推荐方法一。