自定义TextView

在使用textView的时候，我们如果希望它拥有textField的占位文字的功能，就要自定义了。

先看自定义的流程：

下面给出具体的代码：

（后面有注意点讲解）

//.h文件#import <UIKit/UIKit.h>@interface XYLPlaceHodlerTextView : UITextView/**placeholder占位文字*/@PRoperty (nonatomic, copy) NSString *placeholder;/**placeholderColor占位文字颜色*/@property (nonatomic, strong) UIColor *placeholderColor;@end

// .m文件#import "XYLPlaceHodlerTextView.h"@interface XYLPlaceHodlerTextView()/**UILabel*/@property (nonatomic, strong) UILabel *placeholderLabel;@end@implementation XYLPlaceHodlerTextView/** *  懒加载属性，并设置属性的值 */-(UILabel *)placeholderLabel{    if (!_placeholderLabel) {        UILabel *label = [[UILabel alloc]init];        label.font = [UIFont systemFontOfSize:14];        label.textColor = [UIColor grayColor];        label.numberOfLines = 0;        self.placeholderLabel = label;    }    return self.placeholderLabel;}/** *  设置自己的属性 */-(instancetype)initWithFrame:(CGRect)frame{    if (self = [super initWithFrame:frame]) {        self.alwaysBounceVertical = YES;        self.textColor = [UIColor blackColor];        [XYLNotificationCenter addObserver:self selector:@selector(texting) name:UITextViewTextDidChangeNotification object:self];    }    return self;}/** *  监听有文字输入 */-(void)texting{    [self setPlaceholderTextShow];}/** *  设置占位文字的显示 */-(void)setPlaceholderTextShow{    self.placeholderLabel.hidden = self.hasText;}-(void)layoutSubviews{    [super layoutSubviews];    self.placeholderLabel.x = 4;    self.placeholderLabel.y = 8;    self.placeholderLabel.width = self.width - 2 * self.placeholderLabel.x;    [self.placeholderLabel sizeToFit];//这一步很重要，不能遗忘}-(void)setPlaceholder:(NSString *)placeholder{//    _placeholder = placeholder;//此句的意义何在？    self.placeholderLabel.text = placeholder;    [self setNeedsLayout];}-(void)setPlaceholderColor:(UIColor *)placeholderColor{    self.placeholderLabel.textColor = placeholderColor;    [self setNeedsLayout];}-(void)setFont:(UIFont *)font{    [super setFont:font];    self.placeholderLabel.font = font;    [self setNeedsLayout];}-(void)setText:(NSString *)text{    [super setText:text];    [self setPlaceholderTextShow];}-(void)setAttributedText:(NSAttributedString *)attributedText{    [super setAttributedText:attributedText];    [self setPlaceholderTextShow];}@end

注意点：

界面显示步骤是先调用layoutSubviews将所有子控件的位置frame设计好，然后再调用drawRect方法画上去。

layoutSubviews的调用时机：

• init时不会被调用

• 将要真正显示的会调用

• frame发现改变时智能调用

• 滚动、旋转、remove等等时

• 这些时机都是和frame相关的，也是唯一能更新子视图的最好时机