viewDidLoad上的UIRefreshControl [英] UIRefreshControl on viewDidLoad

问题描述

我正在使用以下代码创建UIRefreshControl：

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];
            });
    });
}

效果很好。如果我导航到我的视图，拖动表格，代码运行并显示数据。

It works great. If I navigate to my view, drag the table, the code runs and the data displays.

但是，我想要做的是在'loading '一出现就表明（用户知道某事正在发生）。我尝试添加以下内容：

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];
}

但它似乎不起作用。当我导航到视图时，它看起来像一个常规视图（刷新控件不可见），当我尝试拉动刷新控件时，它从未完成加载。

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.

显然我是以错误的方式解决这个问题。关于我应该如何处理的任何建议？

Obviously I'm going about this the wrong way. Any suggestions on how I should handle this?

推荐答案

试试这个：

- (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];
}

请记住在某个时候调用endRefreshing！

Remember to call endRefreshing at some point!

编辑以添加完整的工作样本：

此示例视图控制器，在iOS6.1中构建和运行root viewcontroller以 UIRefreshControl 开始，当应用程序启动时已经可见并动画化。

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

TSTableViewController.h

@interface TSTableViewController : UITableViewController
@end

TSTableViewController.m

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

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