Loading images asynchronously in IOS UITableView-Solutions

Issue background:

You need to download the picture in each row in UITableView, before using placeholder, and the cache is available after download.

Solution:

Programme one:

Using Sdwebimage:https://github.com/rs/sdwebimage

How to install and use the code that is explained in detail in the Git page, using the specific:

#import <sdwebimage/uiimageview+webcache.h>...-(UITableViewCell *) TableView: (UITableView *) TableView Cellforrowatindexpath: (Nsindexpath *) indexpath{    static NSString *myidentifier = @ "Myidentifier";    UITableViewCell *cell = [TableView dequeuereusablecellwithidentifier:myidentifier];    if (cell = = nil)    {        cell = [[[UITableViewCell alloc] Initwithstyle:uitableviewcellstyledefault                                       Reuseidentifier:myidentifier] autorelease];    }    Here we use the new provided Setimagewithurl:method to load the Web image    [Cell.imageview setimagewithurl:[nsurl U rlwithstring:@ "Http://www.domain.com/path/to/image.jpg"]                   placeholderimage:[uiimage imagenamed:@ " Placeholder.png "];    Cell.textLabel.text = @ "My text";    return cell;}

Scenario Two:

Use iOS's own asynchronous multi-threaded, download a good picture and save it to the cache, and then use the delegate function to update TableView:

-(void) Reloadrowsatindexpaths: (Nsarray *) indexpaths withrowanimation: (uitableviewrowanimation) animation

Initialization

@interface Viewcontroller () @property (Strong, nonatomic)  Nsmutablearray *imagearray; @property (Strong, Nonatomic ) Nscache *imagecache; @property (weak, nonatomic) Iboutlet UITableView *mycustomtableview; @end @implementation viewcontroller-(void) viewdidload {    [super viewdidload];        Self.imagecache = [[Nscache alloc] init];}

TableView delegate Function:

-(Nsinteger) Numberofsectionsintableview: (UITableView *) TableView {return 1;} -(Nsinteger) TableView: (UITableView *) TableView numberofrowsinsection: (nsinteger) Section {//number of rows is the NUM    ber of time zones in the region for the specified section. return 32;} -(UITableViewCell *) TableView: (UITableView *) TableView Cellforrowatindexpath: (Nsindexpath *) Indexpath {NSLog (@)        Cellforrowatindexpath%d ", indexpath.row);    static NSString *myidentifier = @ "Customidentifier";    UITableViewCell *cell = [TableView dequeuereusablecellwithidentifier:myidentifier]; if (cell = = nil) {cell = [[Customtableviewcell alloc] Initwithstyle:uitableviewcellstyledefault reuseidentifier:m    Yidentifier]; } if ([Cell Iskindofclass:[customtableviewcell class]]) {Customtableviewcell *customcell = (Customtablev        Iewcell *) cell;                NSData *imagedata = [Self.imagecache objectforkey:[nsstring stringwithformat:@ "%d", Indexpath.row]]; if (imageData! = Nil) {customCell.customImageView.image = [UIImage imagewithdata:imagedata];                        } else{customCell.customImageView.image = [UIImage imagenamed:@ "Test1"]; Dispatch_async (Dispatch_get_global_queue (Dispatch_queue_priority_default, (unsigned long) NULL), ^ (void) {U                                IImage *image = [self getpicturefromserver];                    if (image = nil) {NSData *tmpimagedata = uiimagepngrepresentation (image);                    [Self.imagecache setobject:tmpimagedata forkey:[nsstring stringwithformat:@ "%d", Indexpath.row]];                                        NSLog (@ "Download image for%d", indexpath.row); [Self Performselectoronmainthread: @selector (reloadtableviewdataatindexpath:) Withobject:indexpath WaitUntilDone:                NO];                } else{//Do nothing.        }            });    }} else{//Do nothing: }    return cell;} 

Reloadtableviewdataatindexpath:

-(void) Reloadtableviewdataatindexpath: (Nsindexpath *) indexpath{NSLog (@ "Mywineviewcontroller:in Reload Collection V    Iew data for index:%d ", indexpath.row);    nsarray* Indexarray = [Nsarray arraywithobjects:indexpath, Nil]; [Self.mycustomtableview Reloadrowsatindexpaths:indexarray withrowanimation:uitableviewrowanimationfade];//[ Self.mycustomtableview Reloadrowsatindexpaths:indexarray withrowanimation:uitableviewrowanimationautomatic];//[ Self.mycustomtableview Reloadrowsatindexpaths:indexarray withrowanimation:uitableviewrowanimationbottom];//[ Self.mycustomtableview Reloadrowsatindexpaths:indexarray withrowanimation:uitableviewrowanimationleft];//[ Self.mycustomtableview Reloadrowsatindexpaths:indexarray withrowanimation:uitableviewrowanimationmiddle];//[ Self.mycustomtableview Reloadrowsatindexpaths:indexarray withrowanimation:uitableviewrowanimationnone];//[ Self.mycustomtableview Reloadrowsatindexpaths:indexarray Withrowanimation:uitableviewrowanimationright];//[Self.mycustomtableview Reloadrowsatindexpaths:indexarray Withrowanimation:uitableviewrowanimationtop] ;}

Download image

-(UIImage *) getpicturefromserver{UIImage *image = nil; NSString *urlstring = [NSString stringwithformat:@ "Http://yourPicture<span style=" font-family:arial, Helvetica, Sans-serif; " >.</span><span style= "font-family:arial, Helvetica, Sans-serif;"    >jpg "];</span> nsmutableurlrequest *request = [[Nsmutableurlrequest alloc] init];    [Request Seturl:[nsurl urlwithstring:urlstring];        [Request sethttpmethod:@ "GET"];    Nsurlresponse *response;    Nserror *connectionerror; NSData *returndata = [nsurlconnection sendsynchronousrequest:request returningresponse:&response error:&    Connectionerror];        if (Connectionerror = = NULL) {Nsinteger StatusCode = [(Nshttpurlresponse *) response StatusCode];                NSLog (@ "Getpicturefromserver-response Status code:%ld", (long) statusCode);        if (StatusCode = =) {image = [UIImage imagewithdata:returndata];        } else{//Do nothing. }    }   else{//Do nothing. } return image;

Scenario Three: (not recommended)

On the basis of scenario two, the change is to download a good picture after the load of the entire tableview, the shortcomings will cause sliding tableview when blocked.

-(void) reloadtableviewdata{    NSLog (@ "Mywineviewcontroller:in Reload Collection View Data");    [Self.mycustomtableview Reloaddata];}

Reference Links:

Http://stackoverflow.com/questions/15290974/uitableview-on-screen-image-download-lazy-loading

Http://stackoverflow.com/questions/7040740/reload-spefic-uitableview-cell-ios

Loading images asynchronously in IOS UITableView-Solutions