如何在按下刷新按钮后自动停止活动指示，并在UITableview JSON中完成内容加载
我已经有代码开始旋转和按钮
这是完整的代码
class ViewController: UIViewController, UITableViewDataSource, UITableViewDelegate {
var json_data_url = "http://www.howtotechworld.com/json_table_view_images%20(1).json"
var image_base_url = ""
var isProgressShowing = true;
var TableData:Array< datastruct > = Array < datastruct >()
enum ErrorHandler:ErrorType
{
case ErrorFetchingResults
}
struct datastruct
{
var imageurl:String?
var description:String?
var image:UIImage? = nil
init(add: NSDictionary)
{
imageurl = add["url"] as? String
description = add["description"] as? String
}
}
@IBOutlet var tableview: UITableView!
override func viewDidLoad() {
super.viewDidLoad()
tableview.dataSource = self
tableview.delegate = self
get_data_from_url(json_data_url)
}
override func viewWillAppear(animated: Bool) {
let barButtonItem = UIBarButtonItem(title: "Refresh", style: .Plain, target: self, action: "refreshTapped");
self.navigationItem.rightBarButtonItem = barButtonItem;
}
func refreshTapped() {
addProgressIndicator(isProgressShowing);
get_data_from_url(json_data_url)
}
func addProgressIndicator(show : Bool) {
isProgressShowing = !show;
if(show) {
let myActivityIndicator = UIActivityIndicatorView(activityIndicatorStyle:UIActivityIndicatorViewStyle.Gray)
myActivityIndicator.startAnimating()
let barButtonItem = UIBarButtonItem(customView: myActivityIndicator)
self.navigationItem.rightBarButtonItem = barButtonItem
} else {
self.navigationItem.rightBarButtonItem = nil;
}
}
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell
{
let cell = tableView.dequeueReusableCellWithIdentifier("cell", forIndexPath: indexPath)
let data = TableData[indexPath.row]
cell.textLabel?.text = data.description
if (data.image == nil)
{
cell.imageView?.image = UIImage(named:"image.jpg")
load_image(image_base_url + data.imageurl!, imageview: cell.imageView!, index: indexPath.row)
}
else
{
cell.imageView?.image = TableData[indexPath.row].image
}
return cell
}
func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int
{
return TableData.count
}
func get_data_from_url(url:String)
{
let url:NSURL = NSURL(string: url)!
let session = NSURLSession.sharedSession()
let request = NSMutableURLRequest(URL: url)
request.HTTPMethod = "GET"
request.cachePolicy = NSURLRequestCachePolicy.ReloadIgnoringCacheData
let task = session.dataTaskWithRequest(request) {
(
let data, let response, let error) in
guard let _:NSData = data, let _:NSURLResponse = response where error == nil else {
print("error")
return
}
dispatch_async(dispatch_get_main_queue(), {
self.extract_json(data!)
return
})
}
task.resume()
}
func extract_json(jsonData:NSData)
{
let json: AnyObject?
do {
json = try NSJSONSerialization.JSONObjectWithData(jsonData, options: [])
} catch {
json = nil
return
}
if let list = json as? NSArray
{
for (var i = 0; i < list.count ; i++ )
{
if let data_block = list[i] as? NSDictionary
{
TableData.append(datastruct(add: data_block))
}
}
do
{
try read()
}
catch
{
}
do_table_refresh()
}
}
func do_table_refresh()
{
dispatch_async(dispatch_get_main_queue(), {
self.tableview.reloadData()
return
})
}
func load_image(urlString:String, imageview:UIImageView, index:NSInteger)
{
let url:NSURL = NSURL(string: urlString)!
let session = NSURLSession.sharedSession()
let task = session.downloadTaskWithURL(url) {
(
let location, let response, let error) in
guard let _:NSURL = location, let _:NSURLResponse = response where error == nil else {
print("error")
return
}
let imageData = NSData(contentsOfURL: location!)
dispatch_async(dispatch_get_main_queue(), {
self.TableData[index].image = UIImage(data: imageData!)
self.save(index,image: self.TableData[index].image!)
imageview.image = self.TableData[index].image
return
})
}
task.resume()
}
func read() throws
{
do
{
let appDelegate = UIApplication.sharedApplication().delegate as! AppDelegate
let managedContext = appDelegate.managedObjectContext!
let fetchRequest = NSFetchRequest(entityName: "Images")
let fetchedResults = try managedContext.executeFetchRequest(fetchRequest)
for (var i=0; i < fetchedResults.count; i++)
{
let single_result = fetchedResults[i]
let index = single_result.valueForKey("index") as! NSInteger
let img: NSData? = single_result.valueForKey("image") as? NSData
TableData[index].image = UIImage(data: img!)
}
}
catch
{
print("error")
throw ErrorHandler.ErrorFetchingResults
}
}
func save(id:Int,image:UIImage)
{
let appDelegate = UIApplication.sharedApplication().delegate as! AppDelegate
let managedContext = appDelegate.managedObjectContext!
let entity = NSEntityDescription.entityForName("Images",
inManagedObjectContext: managedContext)
let options = NSManagedObject(entity: entity!,
insertIntoManagedObjectContext:managedContext)
let newImageData = UIImageJPEGRepresentation(image,1)
options.setValue(id, forKey: "index")
options.setValue(newImageData, forKey: "image")
do {
try managedContext.save()
} catch
{
print("error")
}
}
}
答案 0 :(得分：3)
您需要保留对myActivityIndicator的引用，并在do_table_refresh()中将其停止，如下所示。
func do_table_refresh()
{
dispatch_async(dispatch_get_main_queue(), {
self.tableview.reloadData()
myActivityIndicator.stopAnimating()
return
})
}
编辑：在查看问题中的代码之后，我想了一下。
如果您想使用myActivitIndicator隐藏addProgressIndicator(isProgressShowing)，则必须确保isProgressShowing设置为FALSE，然后在我上面给出的代码中，替换{ {1}} myActivityIndicator.stopAnimating()。
您还需要更新addProgressIndicator(isProgressShowing)功能并将addProgressIndicator添加到其他条件。
答案 1 :(得分：1)
如果我理解你的问题，那么我认为以下是你想要的。
-(void) tableView:(UITableView *)tableView willDisplayCell:(UITableViewCell *)cell forRowAtIndexPath:(NSIndexPath *)indexPath
{
if([indexPath row] == ((NSIndexPath*)[[tableView indexPathsForVisibleRows] lastObject]).row){
//end of loading
//for example [activityIndicator stopAnimating];
}
}
对于swift来说就像这样
func cellForRowAtIndexPath(_ indexPath: NSIndexPath) -> UITableViewCell?{
if(indexPath.row = tableView.indexPathsForVisibleRows().lastObject().row{
//end of loading
//for example [activityIndicator stopAnimating];
}
return yourCell;
}
我不太了解，但我想你会知道怎么做。
答案 2 :(得分：1)
在do_table_refresh()：addProgressIndicator(!isProgressShowing);