照片查看器
/**
用纯代码开发的过程1. 确定界面元素,要有什么内容
2. 用代码来搭建界面
3. 编写代码
*/
@interface HMViewController ()
@property (nonatomic, strong) UILabel *noLabel;
@property (nonatomic, strong) UIImageView *iconImage;
@property (nonatomic, strong) UILabel *descLabel;
@property (nonatomic, strong) UIButton *leftButton;
@property (nonatomic, strong) UIButton *rightButton;
/** 当前显示的照片索引 */
@property (nonatomic, assign) int index;
/** 图片信息的数组 */
@property (nonatomic, strong) NSArray *imageList;
@property (nonatomic, strong) Person *person;
@end
@implementation HMViewController
/**
懒加载(延迟加载),通过getter实现
效果:让对象在最需要的时候才创建!
*/
- (NSArray *)imageList
{
NSLog(@"读取图像信息");
if (_imageList == nil) {
NSString *path = [[NSBundle mainBundle] pathForResource:@"ImageList" ofType:@"plist"];
_imageList = [NSArray arrayWithContentsOfFile:path];
}
return _imageList;
}
#pragma mark - 控件的懒加载
// 在getter方法中,不要再使用self. 否则会重复调用getter方法,造成死循环
- (UILabel *)noLabel
{
if (_noLabel == nil) {
UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(0, 20, self.view.bounds.size.width, 40)];
_noLabel = label;
_noLabel.textAlignment = NSTextAlignmentCenter;
[self.view addSubview:_noLabel];
}
return _noLabel;
}
- (UIImageView *)iconImage
{
if (_iconImage == nil) {
CGFloat imageW = 200;
CGFloat imageH = 200;
CGFloat imageX = (self.view.bounds.size.width - imageW) * 0.5;
CGFloat imageY = CGRectGetMaxY(self.noLabel.frame) + 20;
_iconImage = [[UIImageView alloc] initWithFrame:CGRectMake(imageX, imageY, imageW, imageH)];
[self.view addSubview:_iconImage];
}
return _iconImage;
}
- (UILabel *)descLabel
{
if (_descLabel == nil) {
CGFloat descY = CGRectGetMaxY(self.iconImage.frame);
_descLabel = [[UILabel alloc] initWithFrame:CGRectMake(0, descY, self.view.bounds.size.width, 100)];
_descLabel.textAlignment = NSTextAlignmentCenter;
// 需要Label具有“足够的高度”,不限制显示的行数
_descLabel.numberOfLines = 0;
[self.view addSubview:_descLabel];
}
return _descLabel;
}
- (UIButton *)leftButton
{
if (_leftButton == nil) {
_leftButton = [[UIButton alloc] initWithFrame:CGRectMake(0, 0, 40, 40)];
CGFloat centerY = self.iconImage.center.y;
CGFloat centerX = self.iconImage.frame.origin.x * 0.5;
_leftButton.center = CGPointMake(centerX, centerY);
[_leftButton setBackgroundImage:[UIImage imageNamed:@"left_normal"] forState:UIControlStateNormal];
[_leftButton setBackgroundImage:[UIImage imageNamed:@"left_highlighted"] forState:UIControlStateHighlighted];
[self.view addSubview:_leftButton];
_leftButton.tag = -1;
[_leftButton addTarget:self action:@selector(clickButton:) forControlEvents:UIControlEventTouchUpInside];
}
return _leftButton;
}
- (UIButton *)rightButton
{
if (_rightButton == nil) {
_rightButton = [[UIButton alloc] initWithFrame:CGRectMake(0, 0, 40, 40)];
CGFloat centerY = self.iconImage.center.y;
CGFloat centerX = self.iconImage.frame.origin.x * 0.5;
_rightButton.center = CGPointMake(self.view.bounds.size.width - centerX, centerY);
[_rightButton setBackgroundImage:[UIImage imageNamed:@"right_normal"] forState:UIControlStateNormal];
[_rightButton setBackgroundImage:[UIImage imageNamed:@"right_highlighted"] forState:UIControlStateHighlighted];
[self.view addSubview:_rightButton];
_rightButton.tag = 1;
[_rightButton addTarget:self action:@selector(clickButton:) forControlEvents:UIControlEventTouchUpInside];
}
return _rightButton;
}
/** 在viewDidLoad创建界面 */
- (void)viewDidLoad
{
[super viewDidLoad];
// 显示照片信息
[self showPhotoInfo];
}
/**
重构的目的:让相同的代码只出现一次
*/
- (void)showPhotoInfo
{
// 设置序号
self.noLabel.text = [NSString stringWithFormat:@"%d/%d", self.index + 1, 5];
// 设置图像和描述
self.iconImage.image = [UIImage imageNamed:self.imageList[self.index][@"name"]];
self.descLabel.text = self.imageList[self.index][@"desc"];
self.rightButton.enabled = (self.index != 4);
self.leftButton.enabled = (self.index != 0);
}
// 在OC中,很多方法的第一个参数,都是触发该方法的对象!
- (void)clickButton:(UIButton *)button
{
// 根据按钮调整当前显示图片的索引?
self.index += button.tag;
[self showPhotoInfo];
}
注意:
1)
问题分析:每一次调用showPhotoInfo方法都会实例化一次数组
解决办法:将数组实例化方法移动至viewDidLoad方法
2) 问题分析:
解决办法:将数组实例化方法移动至viewDidLoad方法
2) 问题分析:
1) viewDidLoad方法过于冗长
2) 控件计算位置时,彼此依赖
解决办法:
利用控件的getter方法,实现控件的懒加载
2) 控件计算位置时,彼此依赖
解决办法:
利用控件的getter方法,实现控件的懒加载
3) 问题分析:图片信息与代码的耦合性还是太强
解决办法:采用plist的方式定义图片信息内容
提示:这是从网络加载数据的前奏,在程序开发过程中,应该尽量让数据内容与程序代码分离!