牛骨文教育服务平台(让学习变的简单)

一:效果

二:代码:

由于系统自带的UITextField:和UITextView:不能满足我们的需求,所以我们需要自己设计一个。

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

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

NYTextView.h

//
//  Created by apple on 14-10-20.
//  Copyright (c) 2014年 heima. All rights reserved.
//  增强:带有占位文字

#import <UIKit/UIKit.h>

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

NYTextView.m

//  Created by apple on 14-10-20.
//  Copyright (c) 2014年 heima. All rights reserved.
//

#import "NYTextView.h"

@implementation NYTextView

- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        // 不要设置自己的delegate为自己
//        self.delegate = self;

        // 通知
        // 当UITextView的文字发生改变时,UITextView自己会发出一个UITextViewTextDidChangeNotification通知
        [NYNotificationCenter addObserver:self selector:@selector(textDidChange) name:UITextViewTextDidChangeNotification object:self];
    }
    return self;
}

- (void)dealloc
{
    [NYNotificationCenter 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)setFont:(UIFont *)font
{
    [super setFont:font];

    [self setNeedsDisplay];
}

- (void)drawRect:(CGRect)rect
{
//    [NYRandomColor set];
//    UIRectFill(CGRectMake(20, 20, 30, 30));
    // 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:[UIColor grayColor];
    // 画文字
//    [self.placeholder drawAtPoint:CGPointMake(5, 8) withAttributes:attrs];
    CGFloat x = 5;
    CGFloat w = rect.size.width - 2 * x;
    CGFloat y = 8;
    CGFloat h = rect.size.height - 2 * y;
    CGRect placeholderRect = CGRectMake(x, y, w, h);
    [self.placeholder drawInRect:placeholderRect withAttributes:attrs];
}

@end