ios－同步下载，异步下载，S…

最新推荐文章于 2024-11-19 22:58:57 发布

iOS基地

最新推荐文章于 2024-11-19 22:58:57 发布

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本文介绍iOS应用中图片的同步与异步加载方法，包括如何使用NSURLConnection进行网络请求，实现图片的下载及进度显示。

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原文地址：ios－同步下载，异步下载，SBJson 作者：Lee小刀

www.bejson.com json格式化网站

{

"key1":[

"a",

{

"key2":"value2"

}

]

}

//将内容实例化为字符串对象

NSString* jasonStr = @"{"key1":["a",{"key2":"value2"}]}";

//将字符串对象转为nsdictionary对象

NSDictionary* dic = [jasonStr JSONValue];

//从字典里读取出来的value1是一个数组

NSArray* array = [dic objectForKey:@"key1"];

//从数组中取出对应的dic对象

NSDictionary* dic2 = [array objectAtIndex:1];

NSLog(@"%@", [dic2 objectForKey:@"key2"];

//-----------------------------------------------------------------------------------------------------------

同步下载

//将本地的文件读取出来后实例化nsstring对象

NSString* jsonStr = [NSString stringWithContentsOfFile:[[NSBundle mainBundle] pathForResource:@"douban" ofType:@"txt"] encoding:NSUTF8StringEncoding error:nil];

//加打印判断一下是否读取成功

NSLog(@"%@", jsonStr);

NSDictionary* dic = [jsonStr JSONValue];

NSArray* entryArray = [dic objectForKey:@"entry"];

NSDictionary* book1 = [entryArray objectAtIndex:0];

NSArray* linkArray = [book1 objectForKey:@"link"];

NSDictionary* urldic = [linkArray objectAtIndex:2];

NSString* urlStr = [urldic objectForKey:@"@href"];

NSURL* imageUrl = [NSURL URLWithString:@"http://pic1.desk.chinaz.com/file/11.07.10/8/ershiyiyuezmbz47.jpg" 或<@"urlStr">];

//实例化请求对象

NSURLRequest* request = [NSURLRequest requestWithURL:imageUrl];

//nsdata二进制

NSData* data = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil];

UIImage* image = [UIImage imageWithData:data];

UIImageView* imageView = [[UIImageView alloc] initWithFrame:CGRectMake(100, 100, 150, 150)];

imageView.image = image;

[self.view addSubview:imageView];

[imageView release];

//-------------------------------------------------------------------------------------------------------------------------------------------

异步下载

@interface ViewController : UIViewController<NSURLConnectionDataDelegate>{

UIImageView* imageView;

NSMutableData* imageData;

float currentPro;

float length;

UIProgressView* proView;

//---------------------------------------

@implementation ViewController

- (void)viewDidLoad

{

[super viewDidLoad];

imageView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, 320, 250)];

[self.view addSubview:imageView];

[imageView release];

UIButton* button = [UIButton buttonWithType:UIButtonTypeRoundedRect];

button.frame = CGRectMake(100, 260, 100, 40);

[button setTitle:@"看见我吧" forState:UIControlStateNormal];

[button addTarget:self action:@selector(buttonClick) forControlEvents:UIControlEventTouchUpInside];

[self.view addSubview:button];

imageData = [[NSMutableData alloc] init];

}

- (void)buttonClick{

NSString* urlStr = @"http://pic4.bbzhi.com/fengjingbizhi/2560x1600gaoqingfengjingbizhi/2560x1600gaoqingfengjingbizhi_350068_13.jpg";

NSURLRequest* request = [NSURLRequest requestWithURL:[NSURL URLWithString:urlStr]];

[NSURLConnection connectionWithRequest:request delegate:self];

}

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response{

NSLog(@"开始下载");

NSHTTPURLResponse* http = (NSHTTPURLResponse*)response;

NSDictionary* dic = http.allHeaderFields;

NSString* str = [dic objectForKey:@"Content-Length"];

length = [str floatValue];

proView = [[UIProgressView alloc] initWithFrame:CGRectMake(50, 400, 220, 50)];

//刚开始为0,progress为1时就到头了

proView.progress = currentPro / length;

[self.view addSubview:proView];

[proView release];

}

//时时调用次函数

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data{

[imageData appendData:data];

proView.progress = (float)imageData.length / length;

}

//数据下载完成后调用次函数

- (void)connectionDidFinishLoading:(NSURLConnection *)connection{

imageView.image = [UIImage imageWithData:imageData];

}

- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error{

NSLog(@"error");

}

- (void)dealloc{

[imageData release];

[super dealloc];

}