xcode 如何使用多线程在 UITableView 中显示 json 图像数组？
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How to display json image array in UITableView using multithreading?
提问by madLokesh
I have few images on my server whose names are stored in the phpmysql table. The table contains two fields: id and images. I have prepared a php to fetch the images in json encoded formatted as mentioned:
我的服务器上的图像很少，其名称存储在 phpmysql 表中。该表包含两个字段：id 和图像。我准备了一个 php 来获取 json 编码格式的图像，如下所示：
jsonFetch.php
jsonFetch.php
<?php
$dbhost = "localhost";
$dbname = "userauth";
$dbuser = "root";
//$DB_Pass = "root";
$dbtable = "images";
@mysql_connect($dbhost, $dbuser);
$db = mysql_select_db($dbname);
$sql = "SELECT * FROM $dbtable";
$query = mysql_query($sql);
while($row = mysql_fetch_array($query))
{
$rows[] = array(
//"id" => $row[0],
"image" => $row[1]
//"description" => $row['description']);
);
}
$json = json_encode($rows);
$callback = $_GET['images'];
echo $callback.$json ;
//print_r($json);
?>
Now, when i hit the url, i am getting following response:
现在，当我点击 url 时，我收到以下回复：
[{"image":"./95462"},{"image":"./8838upload_image.jpg"}{"image":"./43185upload_image.jpg"},{"image":"/17426upload_image.jpg"}]
[{"image":"./95462"},{"image":"./8838upload_image.jpg"}{"image":"./43185upload_image.jpg"},{"image":"/17426upload_image.jpg "}]
I am getting json array as above.
我得到了上面的json数组。
The next step is to display the above array in multithreaded manner in UITableView. I am getting the images from url when i hardcode them but when it comes to json parse, i am a noob. I have tried every possible manner in which json can be parsed so for you reference, i am posting the .m file. :
下一步就是在UITableView中以多线程的方式显示上述数组。当我对它们进行硬编码时，我从 url 获取图像，但是当涉及到 json 解析时，我是一个菜鸟。我已经尝试了可以解析 json 的所有可能方式，以便您参考，我正在发布 .m 文件。：
#import "json.h"
@interface profilePhotos(Private)
- (void) initialize;
- (void) loadImage:(id)arg;
- (void) updateTableView:(id)arg;
- (void) addImagesToQueue:(NSArray *)images;
- (void) addImagesToQueue:(NSArray *)arrayImages;
- (void) addImagesToQueue:(NSArray *)arrayDataFromServer;
- (void) showcommentView;
- (void) hidecommentView;
@end
@implementation profilePhotos
@synthesize photosTable;
@synthesize addPhotos;
@synthesize deletePhotos;
@synthesize back;
@synthesize imageQueue, loadedImages, imageLoaderOpQueue, commentView;
//@synthesize photosView;
-(void)initializeWith:(int)buttonTag{
tag = buttonTag;
NSLog(@"tag = %d", tag);
}
- (id) initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
if (!(self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil])) {
return self;
}
[self initialize];
return self;
}
- (void) awakeFromNib
{
NSLog(@"AsyncImageLoadingViewController::awakeFromNib called");
[super awakeFromNib];
[self initialize];
}
- (void) viewDidLoad
{
NSLog(@"AsyncImageLoadingViewController::viewDidLoad called");
[super viewDidLoad];
}
- (void) viewDidAppear:(BOOL)animated
{
NSLog(@"AsyncImageLoadingViewController::viewDidAppear called");
[super viewDidAppear:animated];
NSArray *images = [NSArray arrayWithObjects:
@"http://dl.dropbox.com/u/9234555/avatars/ava01.gif",
@"http://dl.dropbox.com/u/9234555/avatars/ava02.gif",
@"http://dl.dropbox.com/u/9234555/avatars/ava03.gif",
@"http://dl.dropbox.com/u/9234555/avatars/ava04.gif",
@"http://dl.dropbox.com/u/9234555/avatars/ava05.gif", nil];
[self addImagesToQueue:images];
NSLog(@"addImagesToQueue: %@",self);
}
#pragma mark -
#pragma mark Private Methods
/*!
@method
@abstract initializes class variables
*/
- (void) initialize
{
NSLog(@"AsyncImageLoadingViewController::initialize called");
NSMutableArray *a = [[NSMutableArray alloc] init];
self.imageQueue = a;
//[a release];
a = [[NSMutableArray alloc] init];
self.loadedImages = a;
//[a release];
NSOperationQueue *queue = [[NSOperationQueue alloc] init];
self.imageLoaderOpQueue = queue;
//[queue release];
}
/*!
@method
@abstract updates tableview for the newly downloaded image and scrolls the tableview to bottom
*/
- (void) updateTableView:(id)arg
{
NSLog(@"AsyncImageLoadingViewController::updateTableView called");
if ((arg == nil) || ([arg isKindOfClass:[UIImage class]] == NO)) {
return;
}
// store the newly downloaded image
[self.loadedImages addObject:arg];
//[arg release];
// refresh tableview
[self.photosTable reloadData];
// scroll to the last cell of the tableview
NSIndexPath *lastRow = [NSIndexPath indexPathForRow:([self.loadedImages count] - 1) inSection:0];
[self.photosTable scrollToRowAtIndexPath:lastRow
atScrollPosition:UITableViewScrollPositionBottom
animated:YES];
}
/*!
@method
@abstract downloads images, this is the method that dispatches tasks in the operation q ueue
*/
- (void) loadImage:(id)arg
{
NSLog(@"AsyncImageLoadingViewController::loadImage called");
if ((arg == nil) || ([arg isKindOfClass:[NSString class]] == NO)) {
return;
}
// create a local autorelease pool since this code runs not on main thread
//NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
// fetch the image
NSLog(@"AsyncImageLoadingViewController::loadImage - will download image: %@", arg);
NSData *data = [NSData dataWithContentsOfURL:[NSURL URLWithString:arg]];
UIImage *image = [UIImage imageWithData:data];
NSLog(@"image: %@",image);
// update tableview with the downloaded image on main thread
[self performSelectorOnMainThread:@selector(updateTableView:) withObject:image waitUntilDone:NO];
//[pool release];
}
/*!
@method
@abstract adds images to the queue and starts the operation queue to download them
*/
- (void) addImagesToQueue:(NSArray *)images
{
NSLog(@"AsyncImageLoadingViewController::addImagesToQueue called");
[self.imageQueue addObjectsFromArray:images];
NSLog(@"addImagesToQueue Array: %@", self);
// suspend the operation queue
[self.imageLoaderOpQueue setSuspended:YES];
// add tasks to the operation queue
for (NSString *imageUrl in self.imageQueue) {
NSInvocationOperation *op = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(loadImage:) object:imageUrl];
[self.imageLoaderOpQueue addOperation:op];
// [op release];
}
// clear items in the queue and resume the operation queue to start downloading images
[self.imageQueue removeAllObjects];
[self.imageLoaderOpQueue setSuspended:NO];
}
#pragma mark -
#pragma mark UITableViewDataSource Methods
- (NSInteger)tableView:(UITableView *)tableView
numberOfRowsInSection:(NSInteger)section
{
return [self.loadedImages count];
}
- (UITableViewCell *)tableView:(UITableView *)tableView
cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = @"CellIdentifier";
cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil)
{
//cell = [[[UITableViewCell alloc] initWithStyle:UITableViewStyleGrouped reuseIdentifier:CellIdentifier] autorelease];
cell = [[UITableViewCell alloc] initWithStyle:UITableViewStyleGrouped reuseIdentifier:[NSString stringWithFormat:@"cellID%d",indexPath.row]];
cell.accessoryType =UITableViewCellAccessoryNone;
//cell.accessoryType =UITableViewCellAccessoryDisclosureIndicator;
}
for(UIView *subviews in cell.subviews)
[subviews removeFromSuperview];
UIImageView *photo;
photo=[[UIImageView alloc] init];
[photo setImage:[self.loadedImages objectAtIndex:indexPath.row]];
[photo setFrame:CGRectMake(0, 5, 150, 120)];
[cell addSubview:photo];
return cell;
}
-(void)aMethod:(UIButton *)sender{
//[sender tag];
NSIndexPath *indexPath = [photosTable indexPathForCell: (UITableViewCell*)[[sender superview]superview]];
NSLog(@"[sender tag] is %d",[sender tag]);
if([sender tag]==indexPath.row){
textField = (UITextField*)[cell viewWithTag:[sender tag]];
textField.hidden=NO;
}
//}
}
#pragma mark -
#pragma mark UITableViewDelegate Methods
-(void)tableView:(UITableView *)tableView
didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
[tableView deselectRowAtIndexPath:indexPath animated:YES];
}
- (void)didReceiveMemoryWarning
{
// Releases the view if it doesn't have a superview.
[super didReceiveMemoryWarning];
// Release any cached data, images, etc that aren't in use.
}
- (void)viewDidUnload{
// [self setPhotosView:nil];
[self setPhotosTable:nil];
[self setAddPhotos:nil];
[self setDeletePhotos:nil];
[self setBack:nil];
[super viewDidUnload];
// Release any retained subviews of the main view.
// e.g. self.myOutlet = nil;
}
- (BOOL)shouldAutorotateToInterfaceOrientation:( UIInterfaceOrientation)interfaceOrientation
{
// Return YES for supported orientations
return (interfaceOrientation == UIInterfaceOrientationPortrait);
}
I believe that something is needed to be done in viewDidAppear method but what is it i don't understand.
我相信在 viewDidAppear 方法中需要做一些事情，但我不明白它是什么。
Kindly, help me out. I have tried every possible json method . May be i am making some errors in that but i am all the way frustrated. Please help me please.
请帮帮我。我已经尝试了所有可能的 json 方法。可能是我在这方面犯了一些错误，但我一直很沮丧。请帮助我。
采纳答案by Nitin
Dude..use following reference and you will get tutorial as working demo..
老兄..使用以下参考，您将获得教程作为工作演示..
images in UITableView using multithreading
See this reference if you are new in iOS. It's simple
Hope, this will help you...
希望能帮到你...
回答by adali
i suggest you to use SDWebImage
我建议你使用SDWebImage
Web Image This library provides a category for UIImageVIew with support for remote images coming from the web.
Web Image 这个库为 UIImageVIew 提供了一个类别，支持来自 Web 的远程图像。
It provides:
它提供：
An UIImageView category adding web image and cache management to the Cocoa Touch framework An asynchronous image downloader An asynchronous memory + disk image caching with automatic cache expiration handling A guarantee that the same URL won't be downloaded several times A guarantee that bogus URLs won't be retried again and again Performances!
向 Cocoa Touch 框架添加 Web 图像和缓存管理的 UIImageView 类别 异步图像下载器 具有自动缓存过期处理的异步内存 + 磁盘图像缓存 保证不会多次下载相同的 URL 保证不会出现虚假 URL不能一次次重试表演！
