"尝试将第0行插入第0部分,但更新后第0部分只有0行"错误

Question

我有一个应用程序,从他们的联系人列表中选择一个人,并采取他们的名字,姓氏和电子邮件.然后它将名字保存到nsmutablearray并将其放入uitableview单元格中.一旦在模拟器中选择了联系人,我的问题就出现了.

码:

.H:

#import <UIKit/UIKit.h>
#import <AddressBookUI/AddressBookUI.h>

@interface FirstViewController : UIViewController <    ABPeoplePickerNavigationControllerDelegate, UITableViewDelegate, UITableViewDataSource>

- (IBAction)showPicker:(id)sender;

@property (weak, nonatomic) IBOutlet NSString *firstName;

@property (weak, nonatomic) IBOutlet NSString *email;

@property (weak, nonatomic) IBOutlet NSString *lastName;


@property (weak, nonatomic) IBOutlet UITableView *myTableView;

@property (strong, nonatomic) NSMutableArray *contacts;

@end

.M:

#import "FirstViewController.h"

@interface FirstViewController ()

@end

@implementation FirstViewController

@synthesize firstName;

@synthesize email;

@synthesize lastName;

@synthesize contacts;

@synthesize myTableView;


- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    contacts = [[NSMutableArray alloc]initWithObjects:nil];
}

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

#pragma mark - UITableView Datasource

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

-(NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    return contacts.count;
}

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

    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:cellIdentifier];

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

    }

    cell.textLabel.text = [contacts objectAtIndex:indexPath.row];

    return cell;
}

- (IBAction)showPicker:(id)sender {

    ABPeoplePickerNavigationController *picker =
    [[ABPeoplePickerNavigationController alloc] init];
    picker.peoplePickerDelegate = self;

    [self presentModalViewController:picker animated:YES];
}

- (void)peoplePickerNavigationControllerDidCancel:
(ABPeoplePickerNavigationController *)peoplePicker
{
    [self dismissModalViewControllerAnimated:YES];
}


- (BOOL)peoplePickerNavigationController:
(ABPeoplePickerNavigationController *)peoplePicker
      shouldContinueAfterSelectingPerson:(ABRecordRef)person {

    [self displayPerson:person];
    [self dismissModalViewControllerAnimated:YES];

    return NO;
}

- (BOOL)peoplePickerNavigationController:
(ABPeoplePickerNavigationController *)peoplePicker
      shouldContinueAfterSelectingPerson:(ABRecordRef)person
                                property:(ABPropertyID)property
                              identifier:(ABMultiValueIdentifier)identifier
{





    return NO;

}


- (void)displayPerson:(ABRecordRef)person
{
    NSString* name = (__bridge_transfer NSString*)ABRecordCopyValue(person,
                                                                    kABPersonFirstNameProperty);
    self.firstName = name;

    NSString* last = (__bridge_transfer NSString*)ABRecordCopyValue(person,
                                                                    kABPersonLastNameProperty);
    self.lastName = last;


    ABMultiValueRef  emails = ABRecordCopyValue(person, kABPersonEmailProperty);
    NSString *emailId = (__bridge NSString *)ABMultiValueCopyValueAtIndex(emails, 0);//0     for "Home Email" and 1 for "Work Email".

    self.email = emailId;

    if (!(contacts))
    {

        contacts = [[NSMutableArray alloc]init];

    }

    [contacts insertObject:firstName atIndex:0];

    NSIndexPath * indexPath = [NSIndexPath indexPathForRow:0 inSection:0];

    [self.myTableView insertRowsAtIndexPaths:@[indexPath]  withRowAnimation:UITableViewRowAnimationAutomatic];
}




@end

Answer 1

UITableView必须始终与数据源保持同步.如果数据源可以在后台线程中更改,则必须特别小心.

当某些内容添加到数据源时,请尽快调用beginUpdate/insert/endUpdate.您不必担心缓存这些,UITableView会在确定有足够的CPU时间和资源时缓存要执行的更改.

调用endUpdates时,UITable将再次询问dataSource的节和行数.如果直接来自dataSource的节和行的数量,则数字节和行,加上插入,减去删除必须等于numberOfSections和numberOfRowsInSection的结束调用返回的数字.

最后一个提示:避免混合调用'reloadData'和beginUpdate/endUpdate对.使用其中一个,而不是两个.

Answer 2

我遇到了同样的问题.你所要做的就是改变

[self.myTableView insertRowsAtIndexPaths:@[indexPath]withRowAnimation:UITableViewRowAnimationAutomatic];`

至

 [self.myTableView beginUpdates];

 [self.myTableView insertRowsAtIndexPaths:@[indexPath]withRowAnimation:UITableViewRowAnimationAutomatic];

 [self.myTableView endUpdates];

来自UITableView文档

beginUpdates

Begin a series of method calls that insert, delete, or select rows and sections of the receiver.

当你使用时beginUpdates,你必须打电话endUpdates而不是reloadData.

您可以访问https://developer.apple.com/library/ios/documentation/uikit/reference/UITableView_Class/Reference/Reference.html以获取更多UITableView信息.

希望这可以帮助!

Answer 3

上面关于实施的评论-tableView:numberOfRowsInSection:是正确的。断言正在检查返回值，期望它会增加。

但是，由于您没有设置dataSource其UITableView调用（或不调用）不存在的方法并获取0.

您需要将myTableView.dataSource和 （因为您还实现了委托协议）设置myTableView.delegate为self。

您可能还需要类似的东西

- (void)viewDidLoad
{
    [super viewDidLoad];
    [self.myTableView registerClass:[UITableViewCell class] forCellReuseIdentifier:@"Cell"];
    ...
}

"Cell"除非您在其他地方注册，或者您的故事板有一个“原型单元” ，其中包含您的代码要求的标识符。