代码笔记UIView的placeholder的效果

Posted 2020-07-28 菜鸟and小白

一，效果图。

二，工程图。

三，代码。

RootViewController.h

#import <UIKit/UIKit.h>

@interface RootViewController : UIViewController
<UITextViewDelegate>
{
    UITextView *psTextView;
    UILabel *pslabel;
}
@end

 

RootViewController.m

#import "RootViewController.h"

@interface RootViewController ()

@end

@implementation RootViewController

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization
    }
    return self;
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    
    self.title=@"UIView的placeholder的效果";
    
    [self initBackgroundView];

}
#pragma -mark -初始化背景图
-(void)initBackgroundView
{
    UIView *backView=[[UIView alloc]initWithFrame:CGRectMake(0, 0, 320, 480)];
    [self.view addSubview:backView];
    
    psTextView=[[UITextView alloc]initWithFrame:CGRectMake(10, 70, 280, 200)];
    psTextView.text=@"";
    psTextView.backgroundColor=[UIColor yellowColor];
    psTextView.delegate=self;
    psTextView.scrollEnabled=NO;
    [backView addSubview:psTextView];
    
    
    pslabel=[[UILabel alloc]initWithFrame:CGRectMake(15, 140, 280, 20)];
    pslabel.text=@"请输入备注信息";
    pslabel.textColor=[UIColor grayColor];
    pslabel.enabled=NO;
    pslabel.backgroundColor=[UIColor clearColor];
    [backView addSubview:pslabel];

}
#pragma -mark -UITextView Delegate
- (BOOL)textViewShouldBeginEditing:(UITextView *)textView
{
    return YES;
}
-(BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text
{
    
    if (text.length>0) {
        pslabel.hidden=YES;
    }
    
    if ([text isEqualToString:@"\\n"]) {
        [textView resignFirstResponder];
        return NO;
    }
    
    return YES;
}