如何在表或集合视图中实现无限加载？
问题描述：
我建立的文章阅读应用。我从JSON链接中获取数据，如文章图像和标题在uitableview中。如何在表或集合视图中实现无限加载？
我无法在uitableview中实现分页，比如说我的JSON链接是www.example.com & page = 1包含10个文章，每次只有1-10个。
当我像www.example.com的JSON链接串连&页= 2拿到11-20文章列表。
我无法实现我如何在UITableView中加载上滚动的数据，并增加节数与数据行。
这里是我的代码：
int *x=1;
int *inc=10;
@interface ysTableViewController()
{
Reachability *internetReachable;
}
@end
@implementation ysTableViewController
- (id)initWithStyle:(UITableViewStyle)style
{
self = [super initWithStyle:style];
if (self) {
// Custom initialization
}
return self;
}
- (void)viewDidLoad
{
[super viewDidLoad];
[self checkInternetConnection];
UILabel *titleLabel = [[UILabel alloc] initWithFrame:CGRectMake(20,10,0,20)];
titleLabel.textColor = [UIColor blackColor];
titleLabel.backgroundColor = [UIColor clearColor];
titleLabel.text = @"Story";
[self.navigationItem setTitleView:titleLabel];
}
- (void)scrollViewDidScroll:(UIScrollView *)aScrollView {
CGPoint offset = aScrollView.contentOffset;
CGRect bounds = aScrollView.bounds;
CGSize size = aScrollView.contentSize;
UIEdgeInsets inset = aScrollView.contentInset;
float y = offset.y + bounds.size.height - inset.bottom;
float h = size.height;
float reload_distance = 10;
if(y > h + reload_distance) {
NSLog(@"load more rows");
inc=inc+10;
BOOL myBool = [self isNetworkAvailable];
if (myBool)
{
@try {
// for table cell seperator line color
self.tableView.separatorColor = [UIColor colorWithRed:190/255.0 green:190/255.0 blue:190/255.0 alpha:1.0];
// for displaying the previous screen lable with back button in details view controller
UIBarButtonItem *backbutton1 = [[UIBarButtonItem alloc] initWithTitle:@"" style:UIBarButtonItemStyleBordered target:nil action:nil];
[[self navigationItem] setBackBarButtonItem:backbutton1];
_Title1 = [[NSMutableArray alloc] init];
_Author1 = [[NSMutableArray alloc] init];
_Images1 = [[NSMutableArray alloc] init];
_Details1 = [[NSMutableArray alloc] init];
_link1 = [[NSMutableArray alloc] init];
_Date1 = [[NSMutableArray alloc] init];
NSString *urlString=[NSString stringWithFormat:@“www.example.com&page=%d",x];
NSLog(@"xxxxx===%d",x);
NSURL *newUrl=[NSURL URLWithString:urlString];
NSData* data = [NSData dataWithContentsOfURL:newUrl];
NSArray *ys_avatars = [NSJSONSerialization JSONObjectWithData:data options:0 error:nil];
x++;
if(ys_avatars){
for (int j=0;j<ys_avatars.count;j++)
{
[_Title1 addObject:ys_avatars[j][@"title"]];
[_Author1 addObject: ys_avatars[j][@"author"]];
[_Images1 addObject: ys_avatars[j][@"featured_img"]];
[_Details1 addObject:ys_avatars[j][@"content"]];
[_link1 addObject:ys_avatars[j][@"permalink"]];
NSString *newStr=[ys_avatars[j][@"date"] substringToIndex:[ys_avatars[j][@"date"] length]-3];
[_Date1 addObject:newStr];
} }
else
{
NSLog(@"asd");
} }
@catch (NSException *exception) {
}
}
}
}
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
// Return the number of sections.
return 1;
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
// Return the number of rows in the section.
return inc;
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *Cellidentifier1 = @"ysTableViewCell";
ysTableViewCell *cell1 = [tableView dequeueReusableCellWithIdentifier:Cellidentifier1 forIndexPath:indexPath];
// Configure the cell...
long row = [indexPath row];
cell1.TitleLabel1.text = _Title1[row];
cell1.AuthorLabel1.text = _Author1[row];
NSString *yourStoryUrl = [_Images1[indexPath.row] stringByAddingPercentEscapesUsingEncoding:NSASCIIStringEncoding];
if(yourStoryUrl) {
NSArray *subStringsUrl = [yourStoryUrl componentsSeparatedByString:@"/"];
NSString *stripedName = [subStringsUrl lastObject];
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
//Local stored image file path
NSString* filePath =[documentsDirectory stringByAppendingPathComponent:[NSString stringWithFormat:@"%@",stripedName]];
if(filePath) {
UIImage *image = [UIImage imageWithContentsOfFile:filePath];
if(image) {
// Now the image will have been loaded and decoded and is ready to rock for the main thread
ysTableViewCell *updateCell =(id)[tableView cellForRowAtIndexPath:indexPath];
if(updateCell)
updateCell.ThumbImage1.image=image;
cell1.ThumbImage1.image=image;
} else {
dispatch_queue_t taskQ = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
dispatch_async(taskQ, ^{
NSURL *Imageurl = [NSURL URLWithString:yourStoryUrl];
NSData *data = [NSData dataWithContentsOfURL:Imageurl];
UIImage *images1 = [[UIImage alloc] initWithData:data];
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSData *imageData = UIImagePNGRepresentation(images1);
//_imagePath =[documentsDirectory stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.png",stripedName]];
// NSLog((@"pre writing to file"));
if (![imageData writeToFile:filePath atomically:NO])
{
NSLog((@"Failed to cache image data to disk"));
}
else
{
NSLog((@"the cachedImagedPath is %@",filePath));
}
// Now the image will have been loaded and decoded and is ready to rock for the main thread
dispatch_sync(dispatch_get_main_queue(), ^{
ysTableViewCell *updateCell =(id)[tableView cellForRowAtIndexPath:indexPath];
if(updateCell)
updateCell.ThumbImage1.image=images1;
cell1.ThumbImage1.image=images1;
});
});
}
} else {
dispatch_queue_t taskQ = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
dispatch_async(taskQ, ^{
NSURL *Imageurl = [NSURL URLWithString:yourStoryUrl];
NSData *data = [NSData dataWithContentsOfURL:Imageurl];
UIImage *images1 = [[UIImage alloc] initWithData:data];
// NSString *myString = [Imageurl absoluteString];
// NSLog(@"%@",myString);
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSData *imageData = UIImagePNGRepresentation(images1);
_imagePath =[documentsDirectory stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.png",stripedName]];
// NSLog((@"pre writing to file"));
if (![imageData writeToFile:_imagePath atomically:NO])
{
NSLog((@"Failed to cache image data to disk"));
}
else
{
// NSLog((@"the cachedImagedPath is %@",_imagePath));
}
// Now the image will have been loaded and decoded and is ready to rock for the main thread
dispatch_sync(dispatch_get_main_queue(), ^{
ysTableViewCell *updateCell =(id)[tableView cellForRowAtIndexPath:indexPath];
if(updateCell)
updateCell.ThumbImage1.image=images1;
cell1.ThumbImage1.image=images1;
});
});
}
}
return cell1;
}
答
这绝非易事。总体而言，你需要的代码看起来像这样..
注意这一基本例行的四个非常不同的部分。
我从来没有找到工作“一般”的软件包这一问题的解决方案。
再次，看在这个“四节”：他们给你要找的逻辑！
-(void)forTerm:(NSString *)term doPageAfter:(int)doingThisPage
{
doingThisPage = doingThisPage + 1;
if (doingThisPage > 20) return; // never, ever, ever forget that!! heh.
[CLOUD search:term page:doingThisPage then:^(NSArray *thoseTenResults)
{
self.searchSpinner.hidden = YES;
// (step 1) IF IT IS "PAGE 1", we need to re-kick-off the array...
if (doingThisPage == 1)
CLOUD.searchResultsRA = [[NSMutableArray alloc] init];
// (step 2) go ahead and add on these results
if (doingThisPage == 1)
{
[CLOUD.searchResultsRA addObjectsFromArray:thoseTenResults];
[self.searchDisplay safelyReloadBouncyTable];
}
else
{
[self.searchDisplay.collectionView performBatchUpdates:^
{
NSUInteger oldSize = CLOUD.searchResultsRA.count;
[CLOUD.searchResultsRA addObjectsFromArray:thoseTenResults];
NSUInteger newSize = CLOUD.searchResultsRA.count;
NSMutableArray *arrayWithIndexPaths = [NSMutableArray array];
for (NSUInteger i = oldSize; i < newSize; i++)
[arrayWithIndexPaths
addObject:[NSIndexPath indexPathForRow:i inSection:0]];
[self.searchDisplay justSignal];
[self.searchDisplay.collectionView
insertItemsAtIndexPaths:arrayWithIndexPaths];
}
completion:nil];
}
// (step 3) indeed if it's the first page, do a drop-in for fun
if (doingThisPage == 1) [self.searchDisplay.view dropIn:nil];
// (for a "new search" which is now being displayed, in your UX
// there would be some sort of indication of that fact - do it here)
// (step 4) IF there WERE results .. try another page!
if (thoseTenResults.count > 0)
[self forTerm:term doPageAfter:doingThisPage];
// note we are calling this same routine, again!!!
}
];
}
注 - 您的代码太长。你绝对不得不把它分解成小块。每当你有一段约3行的代码时，把它作为一个单独的函数。它几乎是不可能的“读”和帮助您的代码 - 希望它可以帮助！ – Fattie 2014-09-03 08:25:22