UITextView 实现placeholder的方法

本文转载至 http://www.cnblogs.com/easonoutlook/archive/2012/12/28/2837665.html

在UITextField中自带placeholder属性，可以用于提示输入框信息。但是UITextView并不具备此功能

介绍两种方法来实现：

第一种：

初始化UITextView

1. //首先定义UITextView
2. UITextView *textView = [[UITextView alloc] init];
3. textView.font = [UIFont systemFontOfSize:14];
4. textView.frame =CGRectMake(10, 0, cell.contentView.bounds.size.width-20, side);
5. textView.autoresizingMask = UIViewAutoresizingFlexibleHeight | UIViewAutoresizingFlexibleWidth;
6. textView.backgroundColor = [UIColor whiteColor];
7. [cell.contentView addSubview:textView];
8. textView.hidden = NO;
9. textView.delegate = self;
10. //其次在UITextView上面覆盖个UILable,UILable设置为全局变量。
11. uilabel.frame =CGRectMake(17, 8, cell.contentView.bounds.size.width - side+10, 20);
12. uilabel.text = @"请填写审批意见...";
13. uilabel.enabled = NO;//lable必须设置为不可用
14. uilabel.backgroundColor = [UIColor clearColor];
15. [cell.contentView addSubview:uilabel];

实现UITextView的代理

1. -(void)textViewDidChange:(UITextView *)textView
2. {
3. self.examineText =  textView.text;
4. if (textView.text.length == 0) {
5. uilabel.text = @"请填写审批意见...";
6. }else{
7. uilabel.text = @"";
8. }
9. }

第二种：

UITextView 实现 placeholder 及隐藏键盘

#import <Foundation/Foundation.h>

@interface UIPlaceHolderTextView : UITextView {

NSString *placeholder;

UIColor *placeholderColor;

@private

UILabel *placeHolderLabel;

}

@property(nonatomic, retain) UILabel *placeHolderLabel;

@property(nonatomic, retain) NSString *placeholder;

@property(nonatomic, retain) UIColor *placeholderColor;

-(void)textChanged:(NSNotification*)notification;

@end

#import "UIPlaceHolderTextView.h"

@implementation UIPlaceHolderTextView

@synthesize placeHolderLabel;

@synthesize placeholder;

@synthesize placeholderColor;

- (void)dealloc

{

[[NSNotificationCenter defaultCenter] removeObserver:self];

[placeHolderLabel release]; placeHolderLabel = nil;

[placeholderColor release]; placeholderColor = nil;

[placeholder release]; placeholder = nil;

[super dealloc];

}

- (void)awakeFromNib

{

[super awakeFromNib];

[self setPlaceholder:@""];

[self setPlaceholderColor:[UIColor lightGrayColor]];

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(textChanged:) name:UITextViewTextDidChangeNotification object:nil];

}

- (id)initWithFrame:(CGRect)frame

{

if( (self = [super initWithFrame:frame]) )

{

[self setPlaceholder:@""];

[self setPlaceholderColor:[UIColor lightGrayColor]];

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(textChanged:) name:UITextViewTextDidChangeNotification object:nil];

}

return self;

}

- (void)textChanged:(NSNotification *)notification

{

if([[self placeholder] length] == 0)

{

return;

}

if([[self text] length] == 0)

{

[[self viewWithTag:999] setAlpha:1];

}

else

{

[[self viewWithTag:999] setAlpha:0];

}

}

- (void)setText:(NSString *)text {

[super setText:text];

[self textChanged:nil];

}

- (void)drawRect:(CGRect)rect

{

if( [[self placeholder] length] > 0 )

{

if ( placeHolderLabel == nil )

{

placeHolderLabel = [[UILabel alloc] initWithFrame:CGRectMake(8,8,self.bounds.size.width - 16,0)];

placeHolderLabel.lineBreakMode = UILineBreakModeWordWrap;

placeHolderLabel.numberOfLines = 0;

placeHolderLabel.font = self.font;

placeHolderLabel.backgroundColor = [UIColor clearColor];

placeHolderLabel.textColor = self.placeholderColor;

placeHolderLabel.alpha = 0;

placeHolderLabel.tag = 999;

[self addSubview:placeHolderLabel];

}

placeHolderLabel.text = self.placeholder;

[placeHolderLabel sizeToFit];

[self sendSubviewToBack:placeHolderLabel];

}

if( [[self text] length] == 0 && [[self placeholder] length] > 0 )

{

[[self viewWithTag:999] setAlpha:1];

}

[super drawRect:rect];

}

@end

//隐藏键盘，实现UITextViewDelegate

-(BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString*)text

{

if ([text isEqualToString:@"\n"]) {

[m_textView resignFirstResponder];

return NO;

}

return YES;

}