“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 [英] "Attempt to insert row 0 into section 0, but there are only 0 rows in section 0 after the update" Error

问题描述

我有一个应用程序，该应用程序从他们的联系人列表中选择一个人，并使用他们的名字，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。一旦在模拟器中选择了联系人，就会出现我的问题。

I have an app that is selecting a person from their contacts list and takes their First name, last name and email. It then saves the first name to a nsmutablearray and puts it into a uitableview cell. My problem occurs once the contact is selected in the simulator.

代码：

.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

推荐答案

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，则必须格外小心。

UITableView must be kept in sync with the data source at all times. Special care must be taken if the data source can change in a background thread.

向数据源中添加内容后，请尽快调用beginUpdate / insert / endUpdate。 。您不必担心缓存这些，UITableView将在确定有足够的cpu时间和资源时缓存要执行的更改。

When something is added to the data source, call beginUpdate/insert/endUpdate as soon as possible. You don't have to worry about caching these, the UITableView will cache changes to be executed when it determines there is enough cpu time and resources.

在调用endUpdates的那一刻，UITable将再次向dataSource询问节和行的数量。如果您直接从数据源输入的部分和行的数目，则对部分和行的数目加上插入，减去的删除必须等于最终调用numberOfSections和numberOfRowsInSection所返回的数字。

The moment endUpdates is called, the UITable will ask the dataSource for the number of sections and rows again. If your number of sections and row feeds directly from the dataSource, then number sections and rows, plus insertions, minus deletions must equal the numbers returned by the end calls for numberOfSections and numberOfRowsInSection.

最后一个技巧：避免混合使用 reloadData和beginUpdate / endUpdate对。使用一个或另一个，而不是两个都使用。

One last tip: avoid mixing calls to 'reloadData' and beginUpdate/endUpdate pairs. Use one or the other, not both.

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