对于我的MatchCenterViewController，我设置为在MatchCenter中运行viewDidAppear函数，经过2秒的时间间隔。此函数使用文本和图像填充UITableView。问题是，当用户尝试滚动浏览UITableView或点击MatchCenterViewController时出现的任何单元格，直到MatchCenter功能完成加载，应用程序崩溃。
似乎正在发生这种情况，因为如果用户滚动或点击单元格以打开模型“WebViewSegue”，它会与尝试填充/更新表的MatchCenter函数冲突。我想要发生的是，如果用户开始滚动表格或点击单元格，则MatchCenter中的viewDidAppear函数退出。
我将如何形成这种语法，一旦我这样做，我是否必须将它放在'didSelectRowAtIndexPath'和一个单独的函数中，以考虑滚动？
MatchCenterViewController.m：
#import "MatchCenterViewController.h"
#import <UIKit/UIKit.h>
@interface MatchCenterViewController () <UITableViewDataSource, UITableViewDelegate>
@property (nonatomic, strong) UITableView *matchCenter;
@end
@implementation MatchCenterViewController
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
}
return self;
}
- (void)viewDidLoad
{
[super viewDidLoad];
self.matchCenter = [[UITableView alloc] initWithFrame:self.view.bounds style:UITableViewCellStyleSubtitle];
self.matchCenter.frame = CGRectMake(0,50,320,self.view.frame.size.height-100);
_matchCenter.dataSource = self;
_matchCenter.delegate = self;
[self.view addSubview:self.matchCenter];
_matchCenterArray = [[NSArray alloc] init];
}
- (void)viewDidAppear:(BOOL)animated
{
self.matchCenterArray = [[NSArray alloc] init];
// Delay to allow MatchCenter item enough time to be added before pinging ebay
[NSThread sleepForTimeInterval:2];
[PFCloud callFunctionInBackground:@"MatchCenter"
withParameters:@{}
block:^(NSArray *result, NSError *error) {
if (!error) {
_matchCenterArray = result;
[_matchCenter reloadData];
NSLog(@"Result: '%@'", result);
}
}];
}
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
return _matchCenterArray.count;
}
//the part where i setup sections and the deleting of said sections
- (CGFloat)tableView:(UITableView *)tableView heightForHeaderInSection:(NSInteger)section {
return 21.0f;
}
- (CGFloat)tableView:(UITableView *)tableView heightForFooterInSection:(NSInteger)section
{
return 0.01f;
}
- (UIView *)tableView:(UITableView *)tableView viewForHeaderInSection:(NSInteger)section {
UIView *headerView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 320, 21)];
headerView.backgroundColor = [UIColor lightGrayColor];
_searchTerm = [[[[_matchCenterArray objectAtIndex:section] objectForKey:@"Top 3"] objectAtIndex:3]objectForKey:@"Search Term"];
UILabel *headerLabel = [[UILabel alloc] initWithFrame:CGRectMake(8, 0, 250, 21)];
headerLabel.text = [NSString stringWithFormat:@"%@", _searchTerm];
headerLabel.font = [UIFont boldSystemFontOfSize:[UIFont systemFontSize]];
headerLabel.textColor = [UIColor whiteColor];
headerLabel.backgroundColor = [UIColor lightGrayColor];
[headerView addSubview:headerLabel];
UIButton *deleteButton = [UIButton buttonWithType:UIButtonTypeCustom];
deleteButton.tag = section;
deleteButton.frame = CGRectMake(300, 2, 17, 17);
[deleteButton setImage:[UIImage imageNamed:@"xbutton.png"] forState:UIControlStateNormal];
[deleteButton addTarget:self action:@selector(deleteButtonPressed:) forControlEvents:UIControlEventTouchUpInside];
[headerView addSubview:deleteButton];
return headerView;
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
return 3;
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
// Initialize cell
static NSString *CellIdentifier = @"Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (!cell) {
// if no cell could be dequeued create a new one
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier];
}
// No cell seperators = clean design
tableView.separatorColor = [UIColor clearColor];
// title of the item
cell.textLabel.text = _matchCenterArray[indexPath.section][@"Top 3"][indexPath.row][@"Title"];
cell.textLabel.font = [UIFont boldSystemFontOfSize:14];
// price of the item
cell.detailTextLabel.text = [NSString stringWithFormat:@"$%@", _matchCenterArray[indexPath.section][@"Top 3"][indexPath.row][@"Price"]];
cell.detailTextLabel.textColor = [UIColor colorWithRed:0/255.0f green:127/255.0f blue:31/255.0f alpha:1.0f];
// image of the item
NSData *imageData = [NSData dataWithContentsOfURL:[NSURL URLWithString:_matchCenterArray[indexPath.section][@"Top 3"][indexPath.row][@"Image URL"]]];
[[cell imageView] setImage:[UIImage imageWithData:imageData]];
return cell;
}
- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{
return 65;
}
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
self.itemURL = _matchCenterArray[indexPath.section][@"Top 3"][indexPath.row][@"Item URL"];
[self performSegueWithIdentifier:@"WebViewSegue" sender:self];
}
- (void)deleteButtonPressed:(id)sender
{
// links button
UIButton *deleteButton = (UIButton *)sender;
// Define the sections title
NSString *sectionName = _searchTerm = [[[[_matchCenterArray objectAtIndex:deleteButton.tag] objectForKey:@"Top 3"] objectAtIndex:3]objectForKey:@"Search Term"];
// Run delete function with respective section header as parameter
[PFCloud callFunctionInBackground:@"deleteFromMatchCenter"
withParameters:
@{@"searchTerm": sectionName,}
block:^(NSDictionary *result, NSError *error) {
if (!error) {
[PFCloud callFunctionInBackground:@"MatchCenter"
withParameters:@{
@"test": @"Hi",
}
block:^(NSArray *result, NSError *error) {
if (!error) {
_matchCenterArray = result;
[_matchCenter reloadData];
NSLog(@"Result: '%@'", result);
}
}];
}
}];
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
#pragma mark - Navigation
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
WebViewController *controller = (WebViewController *) segue.destinationViewController;
controller.itemURL = self.itemURL;
}
@end
答案 0 :(得分：1)
你在主线程上阻塞了！不好！请参阅此问题：NSThread sleepfortimeinterval blocks main thread
更好的延迟方法是使用GCD。试试这个：
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(2.0 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
[PFCloud callFunctionInBackground:@"MatchCenter"
withParameters:@{}
block:^(NSArray *result, NSError *error) {
if (!error) {
// Might not be necessary, but it would be good to check to make
// sure _matchCenterArray and _matchCenter still exist.
if (_matchCenterArray && _matchCenter) {
// I am not sure if this block is invoked on the main thread
dispatch_async(dispatch_get_main_queue(), ^{
_matchCenterArray = result;
[_matchCenter reloadData];
NSLog(@"Result: '%@'", result);
})
}
}
}];
});