ios的uitextview怎么实现placehold
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发布时间：2022-05-06 15:11
共1个回答
热心网友
时间：2022-07-01 03:41
首先在创建一个CustomTextView来继承UITextView:
@interface CustomTextView : UITextView
@property (nonatomic, retain) NSString *placeholder;
@property (nonatomic, retain) UIColor *placeholderColor;
@end
加入两个property:
@property (nonatomic, retain) NSString *placeholder; //文字
@property (nonatomic, retain) UIColor *placeholderColor; //颜色
下一步就是具体实现了.m文件
先注册UITextViewTextDidChangeNotification来监听文字内容的改变, 初始化一些变量.
- (id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if (self) {
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(textChanged:)
name:UITextViewTextDidChangeNotification
object:nil];
self.autoresizesSubviews = NO;
self.placeholder = @"";
self.placeholderColor = [UIColor lightGrayColor];
}
return self;
}
然后就是最核心的部分, 重写- (void)drawRect:(CGRect)rect
先确定好placeholder的位置(ios7中文字的位置和之前不一样, 所以placeholder也要对应调一下位置),设置好颜色,用NSString的drawInRect:绘制到TextView中.
- (void)drawRect:(CGRect)rect
{
//内容为空时才绘制placeholder
if ([self.text isEqualToString:@""]) {
CGRect placeholderRect;
placeholderRect.origin.y = 8;
placeholderRect.size.height = CGRectGetHeight(self.frame)-8;
if (IOS_VERSION >= 7) {
placeholderRect.origin.x = 5;
placeholderRect.size.width = CGRectGetWidth(self.frame)-5;
} else {
placeholderRect.origin.x = 10;
placeholderRect.size.width = CGRectGetWidth(self.frame)-10;
}
[self.placeholderColor set];
[self.placeholder drawInRect:placeholderRect
withFont:self.font
lineBreakMode:NSLineBreakByWordWrapping
alignment:NSTextAlignmentLeft];
}
}
但- (void)drawRect:(CGRect)rect在self绘制或大小位置改变的时候被调用,我们输入文字是不会被调用的. 所以要调用self的setNeedsDisplay来重新绘制self里面的内容(placeholder).
- (void)textChanged:(NSNotification *)not
{
[self setNeedsDisplay];
}
- (void)setText:(NSString *)text
{
[super setText:text];
[self setNeedsDisplay];
}
一个简单的,带placeholder的TextView就搞定了.如果需要给placeholder设置字体或别的属性, 可以按照上面的思路实现.
