UIRefreshControl on viewDidLoad - ios

Question

I'm using the following code to create a UIRefreshControl:
- (void) viewDidLoad
{
[super viewDidLoad];
UIRefreshControl *refreshControl = [[UIRefreshControl alloc] init];
[refreshControl addTarget:self action:#selector(doLoad) forControlEvents:UIControlEventValueChanged];
self.refreshControl = refreshControl;
}
- (void) doLoad
{
dispatch_async(dispatch_get_global_queue(0, 0), ^{
// Instead of sleeping, I do a webrequest here.
[NSThread sleepForTimeInterval: 5];
dispatch_async(dispatch_get_main_queue(), ^{
[tableView reloadData];
[self.refreshControl endRefreshing];
});
});
}
It works great. If I navigate to my view, drag the table, the code runs and the data displays.
However, what I would like to do is have the view in the 'loading' state as soon as it appears (that way the user knows something is going on). I have tried adding the following:
- (void)viewDidAppear:(BOOL)animated
{
[super viewDidAppear:animated];
[self.refreshControl beginRefreshing];
}
But it does not seem to work. When I navigate to the view, it looks like a regular view (refresh control is not visible), plus when I try to pull the refresh control, it never finished loading.
Obviously I'm going about this the wrong way. Any suggestions on how I should handle this?

Answer 1

Try this:
- (void) viewWillAppear: (BOOL) animated
{
[super viewWillAppear: animated];
self.tableView.contentOffset = CGPointMake(0, -self.refreshControl.frame.size.height);
[self.refreshControl beginRefreshing];
// kick off your async refresh!
[self doLoad];
}
Remember to call endRefreshing at some point!
EDIT to add full working sample:
This sample view controller, built and run in iOS6.1 as the root viewcontroller starts with the UIRefreshControl already visible and animating when the app launches.
TSTableViewController.h
#interface TSTableViewController : UITableViewController
#end
TSTableViewController.m
#import "TSTableViewController.h"
#implementation TSTableViewController
{
NSMutableArray* _dataItems;
}
- (void) viewDidLoad
{
[super viewDidLoad];
self.refreshControl = [UIRefreshControl new];
[self.refreshControl addTarget: self
action: #selector( onRefresh: )
forControlEvents: UIControlEventValueChanged];
}
- (void) viewWillAppear:(BOOL)animated
{
[super viewWillAppear: animated];
self.tableView.contentOffset = CGPointMake(0, -self.refreshControl.frame.size.height);
[self.refreshControl beginRefreshing];
[self onRefresh: nil];
}
- (void) onRefresh: (id) sender
{
double delayInSeconds = 2.0;
dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, (int64_t)(delayInSeconds * NSEC_PER_SEC));
dispatch_after(popTime, dispatch_get_main_queue(), ^(void){
_dataItems = [NSMutableArray new];
for ( int i = 0 ; i < arc4random() % 100 ; i++ )
{
CFUUIDRef uuid = CFUUIDCreate( NULL );
[_dataItems addObject: CFBridgingRelease(CFUUIDCreateString( NULL, uuid)) ];
CFRelease( uuid );
}
[self.refreshControl endRefreshing];
[self.tableView reloadData];
});
}
#pragma mark - Table view data source
- (NSInteger) numberOfSectionsInTableView: (UITableView *) tableView
{
return 1;
}
- (NSInteger) tableView:(UITableView *) tableView numberOfRowsInSection: (NSInteger) section
{
return _dataItems.count;
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
UITableViewCell *cell = [[UITableViewCell alloc] initWithStyle: UITableViewCellStyleDefault
reuseIdentifier: nil];
cell.textLabel.text = [_dataItems objectAtIndex: indexPath.row];
return cell;
}
#end

Answer 2

Manually modifying the contentOffset is insecure and wrong and can lead to unexpected behavior in some cases. This solution works without touching the contentOffset at all:
func showRefreshControl(show: Bool) {
if show {
refreshControl?.beginRefreshing()
tableView.scrollRectToVisible(CGRectMake(0, 0, 1, 1), animated: true)
} else {
refreshControl?.endRefreshing()
}
}

Answer 3

Another option is fire a UIControlEventValueChanged in your viewDidAppear: to trigger an initial refresh.

Answer 4

- (void) viewDidAppear: (BOOL) animated
{
[super viewDidAppear: animated];
UIRefreshControl *refreshControl = [[UIRefreshControl alloc] init];
[refreshControl addTarget:self action:#selector(doLoad) forControlEvents:UIControlEventValueChanged];
self.refreshControl = refreshControl;
[self.refreshControl beginRefreshing];
}
You never set self.refreshControl