ios学习2-图片切换

用到的知识点有：

1.storyboard和viewcontroller.m之间的连线

2.资源文件.plist  使用

3.NSDictionary类的使用

4.NSArray使用

5.UIImageView使用

自己跟着视屏学习做的第二个例子：一共五张图片，点击按钮左右切换显示图片，功能很基础。

写ios程序的步骤：写布局，连线，写action等

就几个布局，拖一拖就好。连线也是。代码如下

#import "ViewController.h"@interface ViewController ()@property (weak, nonatomic) IBOutlet UILabel *noLable;@property (weak, nonatomic) IBOutlet UILabel *descLable;@property (weak, nonatomic) IBOutlet UIImageView *mainView;@property (weak, nonatomic) IBOutlet UIButton *leftBtn;@property (weak, nonatomic) IBOutlet UIButton *rightBtn;@property (assign,nonatomic) int currentPosition;@property (weak, nonatomic) NSArray *imagesData;@end@implementation ViewController-(NSArray *)imagesData{    if (_imagesData == nil) {        NSString *path = [[NSBundle mainBundle] pathForResource:@"imageData" ofType:@"plist"];        _imagesData = [NSArray arrayWithContentsOfFile:path];    }        return _imagesData;}- (void)viewDidLoad {    [super viewDidLoad];    self.currentPosition = 0;    [self changeImage];}- (void)changeImage {    self.noLable.text = [NSString stringWithFormat:@"%d/%d",self.currentPosition + 1,self.imagesData.count];    self.descLable.text = self.imagesData[self.currentPosition][@"desc"];    self.mainView.image = [UIImage imageNamed:self.imagesData[self.currentPosition][@"icon"]];    self.leftBtn.enabled = (self.currentPosition != 0);    self.rightBtn.enabled = (self.currentPosition != (self.imagesData.count - 1));}- (void)didReceiveMemoryWarning {    [super didReceiveMemoryWarning];    // Dispose of any resources that can be recreated.}- (IBAction)right:(UIButton *)sender {    self.currentPosition++;    [self changeImage];}- (IBAction)left:(UIButton *)sender {    self.currentPosition--;    [self changeImage];}@end

初学者，可能理解的不深刻，会先执行viewDidLoad()方法。赋值给currentPosition，然后切换界面。

主要是学习了这些语句的使用：

1.重写了imagesData方法，这样用点运算，获取变量时，就会对变量进行赋值。

-(NSArray *)imagesData{    if (_imagesData == nil) {        NSString *path = [[NSBundle mainBundle] pathForResource:@"imageData" ofType:@"plist"];        _imagesData = [NSArray arrayWithContentsOfFile:path];    }        return _imagesData;}

同时，学习了plist文件的使用，plist文件本质是一个xml文件，可以当作数据进行初始化的数据，先获取路径path，然后根据path初始化数组。

2.nsbutton设置状态：起到改变颜色的效果

self.rightBtn.enabled = (self.currentPosition != (self.imagesData.count - 1));

3.NSDictionary对象调用的时候用   obj［@“属性名字”］

self.descLable.text = self.imagesData[self.currentPosition][@"desc"];