UITableView cellForRowAtIndexPath 没有被调用

Question

我知道没有调用 cellForRowAtIndexPath 方法，因为我从未在其中看到 NSLog 消息。我已经设置了 UITableView 的 dataSource 和 delegate 属性，并且还在头文件中声明了 UITableViewDelegate 和 UITableViewDataSource。我错过了什么？

- (void)viewDidLoad {
[self.view setBackgroundColor:[UIColor grayColor]];
tableData = [[NSMutableArray alloc] init];
matchesForUser = [[NSMutableArray alloc] init];
sortedFirstArray = [[NSArray alloc] init];
sortedSecondArray = [[NSArray alloc] init];

_tableView = [[UITableView alloc] initWithFrame:CGRectMake(0, 20, self.view.frame.size.width, self.view.frame.size.height - 20) style:UITableViewStylePlain];
_tableView.dataSource = self;
_tableView.delegate = self;
[self.view addSubview:_tableView];

countUsers = 0;
PFQuery *query = [PFQuery queryWithClassName:@"_User"];
[query findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {
    if (!error) {
        for (PFObject *object in objects) {
            NSLog(@"%@", object.objectId);
            tableData[countUsers] = [object valueForKey:@"username"];
            matchesForUser[countUsers] = [object valueForKey:@"matches"];
        }
    }else{
        NSLog([error description]);
    }

    NSLog(@"***tabledata***");
    NSLog([NSString stringWithFormat:@"%lu", (unsigned long)[tableData count]]);
    NSLog(@"***matchesdata***");
    NSLog([NSString stringWithFormat:@"%lu", (unsigned long)[matchesForUser count]]);
}];

dictionary = [NSDictionary dictionaryWithObjects:matchesForUser forKeys:tableData];
sortedFirstArray = [[dictionary allKeys] sortedArrayUsingSelector:@selector(compare:)];
sortedSecondArray = [dictionary objectsForKeys:sortedFirstArray notFoundMarker:[NSNull null]];

backToMap = [[UIButton alloc] initWithFrame:CGRectMake(80, 518, 160, 30)];
backToMap.backgroundColor = [UIColor colorWithRed:33.0f/255.0f green:156.0f/255.0f blue:41.0f/255.0f alpha:1.0f];
[backToMap addTarget:self action:@selector(dismiss) forControlEvents:UIControlEventTouchUpInside];
[backToMap setTitle:@"BACK TO MAP" forState:UIControlStateNormal];
[self.view addSubview:backToMap];
}

- (void)dismiss {
    [self dismissViewControllerAnimated:YES completion:nil];
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
    return [tableData count];
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    static NSString *simpleTableIdentifier = @"SimpleTableItem";

    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:simpleTableIdentifier];

    if (cell == nil) {
        cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:simpleTableIdentifier];
    }

    NSString *username = [[sortedFirstArray objectAtIndex:indexPath.row] stringByAppendingString:@" "];
    NSString *matchAmount = [sortedSecondArray objectAtIndex:indexPath.row];

    NSLog(@"***username***");
    NSLog(username);
    NSLog(@"***matchamount***");
    NSLog(matchAmount);

    cell.textLabel.text = [username stringByAppendingString:matchAmount];

    return cell;
}

Answer 1

您是否在 ViewDidLoad 中重新加载了 Tableview？喜欢

[_tableView reloadData];

Answer 2

尝试做以下事情

1.) 像

一样注册你的tableView

[_tableView registerClass:[UITableViewCell class] forCellReuseIdentifier:@"SimpleTableItem"];

2.) 然后在

下面添加 [_tableView reloadData];

for (PFObject *object in objects) {
        NSLog(@"%@", object.objectId);
        tableData[countUsers] = [object valueForKey:@"username"];
        matchesForUser[countUsers] = [object valueForKey:@"matches"];
    }

内部 if (!error) 部分..

所以你的更新代码必须看起来像

[query findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {
if (!error) {
    for (PFObject *object in objects) {
        NSLog(@"%@", object.objectId);
        tableData[countUsers] = [object valueForKey:@"username"];
        matchesForUser[countUsers] = [object valueForKey:@"matches"];
    }
    [_tableView reloadData];
}else{
    NSLog([error description]);
}

NSLog(@"***tabledata***");
NSLog([NSString stringWithFormat:@"%lu", (unsigned long)[tableData count]]);
NSLog(@"***matchesdata***");
NSLog([NSString stringWithFormat:@"%lu", (unsigned long)[matchesForUser count]]);
}];

Answer 3

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
return [tableData count];
}

count是0？您可以键入 NSLog("%@", @(tableData.count)); 或仅键入 return 1; 进行测试。 UITableView先发送tableView:numberOfRowsInSection:，如果方法return0.它不会调用cellForRowAtIndexPath。

正如@PiyushSharma 提到的，你应该 Register your tableView。

Answer 4

后重新加载 table

dictionary = [NSDictionary dictionaryWithObjects:matchesForUser forKeys:tableData];
sortedFirstArray = [[dictionary allKeys] sortedArrayUsingSelector:@selector(compare:)];
sortedSecondArray = [dictionary objectsForKeys:sortedFirstArray notFoundMarker:[NSNull null]];

[_tableView reloadData];

Answer 5

1) 在这里你确实需要使用 countUsers = 0;如果你需要比你需要增加 for 循环中的值 1.Otherwise 它会覆盖每次索引 0 处的值。

2) 您正在使用后台调用方法来获取 data.So 获取数据需要时间，控制将进一步执行 code.But 届时 matchesForUser 数组 为空，dictionary 也在单元格中 empty.So 它不会显示任何内容，您也不会从单元格中看到 NSLOG。

而不是这个

ini

dictionary = [NSDictionary dictionaryWithObjects:matchesForUser forKeys:tableData];
sortedFirstArray = [[dictionary allKeys] sortedArrayUsingSelector:@selector(compare:)];
sortedSecondArray = [dictionary objectsForKeys:sortedFirstArray notFoundMarker:[NSNull null]];

3) 试试这个，

PFQuery *query = [PFQuery queryWithClassName:@"_User"];
[query findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {
    dispatch_async(dispatch_get_main_queue(), ^{
        if (!error) {
            for (PFObject *object in objects) {
                NSLog(@"%@", object.objectId);
                [tableData addObject:[object valueForKey:@"username"]];
                [matchesForUser addObject:[object valueForKey:@"matches"]];
            }
            dictionary = [NSDictionary dictionaryWithObjects:matchesForUser forKeys:tableData];
            sortedFirstArray = [[dictionary allKeys] sortedArrayUsingSelector:@selector(compare:)];
            sortedSecondArray = [dictionary objectsForKeys:sortedFirstArray notFoundMarker:[NSNull null]];
            [_tableView reloadData];

        }else{
            NSLog([error description]);
        }

        NSLog(@"***tabledata***");
        NSLog([NSString stringWithFormat:@"%lu", (unsigned long)[tableData count]]);
        NSLog(@"***matchesdata***");
        NSLog([NSString stringWithFormat:@"%lu", (unsigned long)[matchesForUser count]]);
    });
}];

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