The placeholder property in Ios&uitextview

A look at the title, it is very cock silk!

Yes, the system is not for us, so let's do it ourselves!

Specific steps:

1, create a class, inherit Uitextview. Name Zhhtextview;

2, in DrawRect: Implement the placeholder, which uses the notification to listen to the change of text.

The approximate step is two steps, concrete implementation, look at the code. < A line of code to solve thousands of words >

Now publish the. m file code as follows:

#import "ZHHTextView.h"

@implementation Zhhtextview

-(Instancetype) initWithFrame: (CGRect) Frame {

if (self = [Super Initwithframe:frame]) {

NSLog (@ "%s", __func__);

Registration notice. The purpose of the notification: The change of listening content

[[Nsnotificationcenter Defaultcenter] addobserver:self selector: @selector (viewtextchange) Name: Uitextviewtextdidchangenotification Object:nil];

}

return self;

}

-(void) Viewtextchange {

To execute this method, the system automatically calls DrawRect: Method

[Self setneedsdisplay];

NSLog (@ "%s", __func__);

}

-(void) Dealloc {

Cancel the notice, you do not cancel to try to see if your project will collapse

[[Nsnotificationcenter Defaultcenter] removeobserver:self];

}

Only override Drawrect:if perform custom drawing.

An empty implementation adversely affects performance during animation.

-(void) DrawRect: (cgrect) Rect {

Drawing Code

If there is content, the return

if (Self.hastext) return;

adding attributes to Placeholder

Nsmutabledictionary *attributes = [Nsmutabledictionary dictionary];

It's better to sync with Self.font here.

Attributes[nsfontattributename] = [Uifont systemfontofsize:15.0];

Attributes[nsforegroundcolorattributename] = [Uicolor graycolor];

In fact, placeholder is painted, since it is painted, must be given the specific location and size

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);

nsstring* placeholder = @ "Please enter the QQ of Hung song ...";

This is a classic method.

[Placeholder Drawinrect:placeholderrect withattributes:attributes];

}

@end

It's OK.

The placeholder property in Ios&uitextview