UITableViewController不会调用cellForRowAtIndexPath但是numberOfSectionsInTableView和numberOfRowsInSection确实设置得当

Question

#import "AssignmentsViewController.h"
#import "Assignment.h"

@interface AssignmentsViewController ()

@property NSMutableArray *assignments;
@property (weak, nonatomic) IBOutlet UITableView *tableView;

@end

@implementation AssignmentsViewController

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization
    }
    return self;
}

- (void)viewDidLoad
{
    NSLog(@"viewDidLoad");
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    self.assignments = [[MySingleton sharedMySingleton] assignments];
    self.tableView.delegate = self;
    self.tableView.dataSource = self;
}

- (void)viewWillAppear:(BOOL)animated {
    NSLog(@"viewWillAppear");
    [self.tableView reloadData];
}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
    NSLog(@"numberOfSectionsInTableView");
    return 1;
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
    NSLog(@"numberOfRowsInSection");
    return [self.assignments count];
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    NSLog(@"cellForRowAtIndexPath");
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"AssignmentCell"];
    if(cell == nil) {
        cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:@"AssignmentCell"];
    }
    cell.textLabel.text = [[self.assignments objectAtIndex:indexPath.row] title];
    return cell;
}

@end

加载AssignmentsViewController并且至少有一个家庭作业在assignments数组中时,控制台输出:

2013-11-06 18:55:09.396 Homework Planner[4756:70b] viewDidLoad
2013-11-06 18:55:09.403 Homework Planner[4756:70b] numberOfSectionsInTableView
2013-11-06 18:55:09.405 Homework Planner[4756:70b] numberOfRowsInSection
2013-11-06 18:55:09.408 Homework Planner[4756:70b] viewWillAppear
2013-11-06 18:55:09.409 Homework Planner[4756:70b] numberOfSectionsInTableView
2013-11-06 18:55:09.409 Homework Planner[4756:70b] numberOfRowsInSection

我正在创建一个显示用户家庭作业的应用程序.由于某种原因,即使我确定赋值数组中有一个家庭作业分配对象,也从不调用cellForRowAtIndexPath.通过模态视图将作业分配添加到数组中,并且我已经验证它们确实是由该过程添加的,并且在用户点击"取消"之后视图返回到由该类定义的视图.当发生这种情况时,另外两个与UITableView相关的方法运行,而不是与cellForRowAtIndexPath相关.请帮我解决这个问题.

Answer 1

让我再提出一个罪魁祸首:"内存管理问题".

如果TableView的DataSource对象没有保留(保留计数为零)而TableView正在从中提取数据,那么,令人惊讶的是,尽管numberOfSections和numberOfRows刚刚被调用,但不会调用tableView:cellForRowAtIndexPath:

Answer 2

检查是否[self.assignments count]返回0(检查是否self.assignments是nil.

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
    NSLog(@"[self.assignments count] = %d", [self.assignments count]);
}

否则,我现在能想到的另一个原因是,当委托方法返回的高度为0时(如果你正在实现它,否则默认实现总是给出非零高度,所以在这种情况下没有问题.)

- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{
  CGFloat height = 0;
  // Some calculation to determine height of row/cell.

  return height;
}