[b]懒加载[/b]
1.懒加载基本
懒加载——也称为延迟加载，即在需要的时候才加载（效率低，占用内存小）。所谓懒加载，写的是其get方法.
注意：如果是懒加载的话则一定要注意先判断是否已经有了，如果没有那么再去进行实例化
2.使用懒加载的好处：
（1）不必将创建对象的代码全部写在viewDidLoad方法中，代码的可读性更强
（2）每个控件的getter方法中分别负责各自的实例化处理，代码彼此之间的独立性强，松耦合
3.代码示例
//
// YYViewController.m
// 03-图片浏览器初步
//
// Created by apple on 14-5-21.
// Copyright (c) 2014年 itcase. All rights reserved.
//
#import "YYViewController.h"
#define POTOIMGW 200
#define POTOIMGH 300
#define POTOIMGX 60
#define POTOIMGY 50
@interface YYViewController ()
@property(nonatomic,strong)UILabel *firstlab;
@property(nonatomic,strong)UILabel *lastlab;
@property(nonatomic,strong)UIImageView *icon;
@property(nonatomic,strong)UIButton *leftbtn;
@property(nonatomic,strong)UIButton *rightbtn;
@property(nonatomic,strong)NSArray *array;
@property(nonatomic ,assign)int i;
-(void)change;
@end
@implementation YYViewController
- (void)viewDidLoad
{
[super viewDidLoad];
[self change];
}
-(void)change
{
[self.firstlab setText:[NSString stringWithFormat:@"%d/5",self.i+1]];
//先get再set
self.icon.image=[UIImage imageNamed:self.array[self.i][@"name"]];
self.lastlab.text=self.array[self.i][@"desc"];
self.leftbtn.enabled=(self.i!=0);
self.rightbtn.enabled=(self.i!=4);
}
//延迟加载
/**1.图片的序号标签*/
-(UILabel *)firstlab
{
//判断是否已经有了，若没有，则进行实例化
if (!_firstlab) {
_firstlab=[[UILabel alloc]initWithFrame:CGRectMake(20, 10, 300, 30)];
[_firstlab setTextAlignment:NSTextAlignmentCenter];
[self.view addSubview:_firstlab];
}
return _firstlab;
}
/**2.图片控件的延迟加载*/
-(UIImageView *)icon
{
//判断是否已经有了，若没有，则进行实例化
if (!_icon) {
_icon=[[UIImageView alloc]initWithFrame:CGRectMake(POTOIMGX, POTOIMGY, POTOIMGW, POTOIMGH)];
UIImage *image=[UIImage imageNamed:@"biaoqingdi"];
_icon.image=image;
[self.view addSubview:_icon];
}
return _icon;
}
/**3.描述控件的延迟加载*/
-(UILabel *)lastlab
{
//判断是否已经有了，若没有，则进行实例化
if (!_lastlab) {
_lastlab=[[UILabel alloc]initWithFrame:CGRectMake(20, 400, 300, 30)];
[_lastlab setTextAlignment:NSTextAlignmentCenter];
[self.view addSubview:_lastlab];
}
return _lastlab;
}
/**4.左键按钮的延迟加载*/
-(UIButton *)leftbtn
{
//判断是否已经有了，若没有，则进行实例化
if (!_leftbtn) {
_leftbtn=[UIButton buttonWithType:UIButtonTypeCustom];
_leftbtn.frame=CGRectMake(0, self.view.center.y, 40, 40);
[_leftbtn setBackgroundImage:[UIImage imageNamed:@"left_normal"] forState:UIControlStateNormal];
[_leftbtn setBackgroundImage:[UIImage imageNamed:@"left_highlighted"] forState:UIControlStateHighlighted];
[self.view addSubview:_leftbtn];
[_leftbtn addTarget:self action:@selector(leftclick:) forControlEvents:UIControlEventTouchUpInside];
}
return _leftbtn;
}
/**5.右键按钮的延迟加载*/
-(UIButton *)rightbtn
{
if (!_rightbtn) {
_rightbtn=[UIButton buttonWithType:UIButtonTypeCustom];
_rightbtn.frame=CGRectMake(POTOIMGX+POTOIMGW+10, self.view.center.y, 40, 40);
[_rightbtn setBackgroundImage:[UIImage imageNamed:@"right_normal"] forState:UIControlStateNormal];
[_rightbtn setBackgroundImage:[UIImage imageNamed:@"right_highlighted"] forState:UIControlStateHighlighted];
[self.view addSubview:_rightbtn];
[_rightbtn addTarget:self action:@selector(rightclick:) forControlEvents:UIControlEventTouchUpInside];
}
return _rightbtn;
}
//array的get方法
-(NSArray *)array
{
if (_array==nil) {
NSString *path=[[NSBundle mainBundle] pathForResource:@"data" ofType:@"plist"];
_array=[[NSArray alloc]initWithContentsOfFile:path];
}
return _array;
}
-(void)rightclick:(UIButton *)btn
{
self.i++;
[self change];
}
-(void)leftclick:(UIButton *)btn
{
self.i--;
[self change];
}
@end
[b]xib的简单使用
[/b]一、简单介绍
xib和storyboard的比较，一个轻量级一个重量级。
共同点：
都用来描述软件界面
都用Interface Builder工具来编辑
不同点:
Xib是轻量级的，用来描述局部的UI界面
Storyboard是重量级的，用来描述整个软件的多个界面，并且能展示多个界面之间的跳转关系
二、xib的简单使用
1.建立xib文件
[img]http://files.jb51.net/file_images/article/201601/20161692144005.png?20160692155[/img]
建立的xib文件命名为appxib.xib
[img]http://files.jb51.net/file_images/article/201601/20161692208829.png?20160692216[/img]
2.对xib进行设置
根据程序的需要，这里把view调整为自由布局
[img]http://files.jb51.net/file_images/article/201601/20161692224532.png?20160692232[/img]
建立view模型（设置长宽等参数）
[img]http://files.jb51.net/file_images/article/201601/20161692240380.png?20160692248[/img]
调整布局和内部的控件
[img]http://files.jb51.net/file_images/article/201601/20161692256070.png?2016069233[/img]
完成后的单个view
[img]http://files.jb51.net/file_images/article/201601/20161692311688.png?20160692317[/img]
3.使用xib文件的代码示例
YYViewController.m文件代码如下：
//
// YYViewController.m
// 10-xib文件的使用
//
// Created by apple on 14-5-24.
// Copyright (c) 2014年 itcase. All rights reserved.
//
#import "YYViewController.h"
#import "YYapp.h"
@interface YYViewController ()
@property(nonatomic,strong)NSArray *app;
@end
@implementation YYViewController
//1.加载数据信息
-(NSArray *)app
{
if (!_app) {
NSString *path=[[NSBundle mainBundle]pathForResource:@"app.plist" ofType:nil];
NSArray *temparray=[NSArray arrayWithContentsOfFile:path];
//字典转模型
NSMutableArray *arrayM=[NSMutableArray array ];
for (NSDictionary *dict in temparray) {
[arrayM addObject:[YYapp appWithDict:dict]];
}
_app=arrayM;
}
return _app;
}
//创建界面原型
- (void)viewDidLoad
{
[super viewDidLoad];
NSLog(@"%d",self.app.count);
//九宫格布局
int totalloc=3;
CGFloat appviewW=80;
CGFloat appviewH=90;
CGFloat margin=(self.view.frame.size.width-totalloc*appviewW)/(totalloc+1);
int count=self.app.count;
for (int i=0; i<count; i++) {
int row=i/totalloc;
int loc=i%totalloc;
CGFloat appviewX=margin + (margin +appviewW)*loc;
CGFloat appviewY=margin + (margin +appviewH)*row;
YYapp *app=self.app[i];
//拿出xib视图
NSArray *apparray= [[NSBundle mainBundle]loadNibNamed:@"appxib" owner:nil options:nil];
UIView *appview=[apparray firstObject];
//加载视图
appview.frame=CGRectMake(appviewX, appviewY, appviewW, appviewH);
UIImageView *appviewImg=(UIImageView *)[appview viewWithTag:1];
appviewImg.image=app.image;
UILabel *appviewlab=(UILabel *)[appview viewWithTag:2];
appviewlab.text=app.name;
UIButton *appviewbtn=(UIButton *)[appview viewWithTag:3];
[appviewbtn addTarget:self action:@selector(appviewbtnClick:) forControlEvents:UIControlEventTouchUpInside];
appviewbtn.tag=i;
[self.view addSubview:appview];
}
}
/**按钮的点击事件*/
-(void)appviewbtnClick:(UIButton *)btn
{
YYapp *apps=self.app[btn.tag];
UILabel *showlab=[[UILabel alloc]initWithFrame:CGRectMake(60, 450, 200, 20)];
[showlab setText:[NSString stringWithFormat: @"%@下载成功",apps.name]];
[showlab setBackgroundColor:[UIColor lightGrayColor]];
[self.view addSubview:showlab];
showlab.alpha=1.0;
//简单的动画效果
[UIView animateWithDuration:2.0 animations:^{
showlab.alpha=0;
} completion:^(BOOL finished) {
[showlab removeFromSuperview];
}];
}
@end
运行效果：
[img]http://files.jb51.net/file_images/article/201601/20161692327964.png?20160692335[/img]
三、对xib进行连线示例
1.连线示例
新建一个xib对应的视图类，继承自Uiview
[img]http://files.jb51.net/file_images/article/201601/20161692347466.png?20160692354[/img]
在xib界面右上角与新建的视图类进行关联
[img]http://files.jb51.net/file_images/article/201601/20161692403139.png?20160692410[/img]
把xib和视图类进行连线
[img]http://files.jb51.net/file_images/article/201601/20161692418905.png?20160692426[/img]
注意：在使用中把weak改成为强引用。否则...
2.连线后的代码示例
YYViewController.m文件代码如下：
//
// YYViewController.m
// 10-xib文件的使用
//
// Created by apple on 14-5-24.
// Copyright (c) 2014年 itcase. All rights reserved.
//
#import "YYViewController.h"
#import "YYapp.h"
#import "YYappview.h"
@interface YYViewController ()
@property(nonatomic,strong)NSArray *app;
@end
@implementation YYViewController
//1.加载数据信息
-(NSArray *)app
{
if (!_app) {
NSString *path=[[NSBundle mainBundle]pathForResource:@"app.plist" ofType:nil];
NSArray *temparray=[NSArray arrayWithContentsOfFile:path];
//字典转模型
NSMutableArray *arrayM=[NSMutableArray array ];
for (NSDictionary *dict in temparray) {
[arrayM addObject:[YYapp appWithDict:dict]];
}
_app=arrayM;
}
return _app;
}
//创建界面原型
- (void)viewDidLoad
{
[super viewDidLoad];
NSLog(@"%d",self.app.count);
//九宫格布局
int totalloc=3;
CGFloat appviewW=80;
CGFloat appviewH=90;
CGFloat margin=(self.view.frame.size.width-totalloc*appviewW)/(totalloc+1);
int count=self.app.count;
for (int i=0; i<count; i++) {
int row=i/totalloc;
int loc=i%totalloc;
CGFloat appviewX=margin + (margin +appviewW)*loc;
CGFloat appviewY=margin + (margin +appviewH)*row;
YYapp *app=self.app[i];
//拿出xib视图
NSArray *apparray= [[NSBundle mainBundle]loadNibNamed:@"appxib" owner:nil options:nil];
//注意这里的类型名!
//UIView *appview=[apparray firstObject];
YYappview *appview=[apparray firstObject];
//加载视图
appview.frame=CGRectMake(appviewX, appviewY, appviewW, appviewH);
[self.view addSubview:appview];
appview.appimg.image=app.image;
appview.applab.text=app.name;
appview.appbtn.tag=i;
[ appview.appbtn addTarget:self action:@selector(appviewbtnClick:) forControlEvents:UIControlEventTouchUpInside];
}
}
/**按钮的点击事件*/
-(void)appviewbtnClick:(UIButton *)btn
{
YYapp *apps=self.app[btn.tag];
UILabel *showlab=[[UILabel alloc]initWithFrame:CGRectMake(60, 450, 200, 20)];
[showlab setText:[NSString stringWithFormat: @"%@下载成功",apps.name]];
[showlab setBackgroundColor:[UIColor lightGrayColor]];
[self.view addSubview:showlab];
showlab.alpha=1.0;
//简单的动画效果
[UIView animateWithDuration:2.0 animations:^{
showlab.alpha=0;
} completion:^(BOOL finished) {
[showlab removeFromSuperview];
}];
}
@end
YYappview.h文件代码（已经连线）
#import <UIKit/UIKit.h>
@interface YYappview : UIView
@property (strong, nonatomic) IBOutlet UIImageView *appimg;
@property (strong, nonatomic) IBOutlet UILabel *applab;
@property (strong, nonatomic) IBOutlet UIButton *appbtn;
@end
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