ios - UITableView reloadData 什么都不做(UITableView 不是 nil)

Question

我正在构建我的第一个真正的应用程序，你们已经提供了最大的帮助，但我一直在为 tableView 不更新而苦苦挣扎。我希望这里的某个人可以阐明这一点，并且可能对我可能错过或做的不必要的复杂的其他事情提出任何想法。

目前，该应用程序应该执行以下操作:

1. 用 sqlite 数据库中的数据填充表(基本上只是列出所有表)
2. 用户按下按钮(触发 fetchData 方法)
3. (void)fetchData 将本地数据库与服务器数据库校验和进行比较
4. (void)fetchData 设置一个 NSURLConnection，通过 POST 与服务器通信
5. 当连接接收到所有数据后，它更新本地数据库
6. tableView 数据源(它是一个 NSMutableArray)用新的数据库数据更新
7. tableview 得到更新并列出数据库中的所有表 [myTableView reloadData] 被调用

我仔细检查过的事情:tableview 和 delegate、datasource 和 outlet 之间的连接； tableView 不为零；数据源本身已准确更新；

到最后一点 (7) 为止一切正常。 myTableView 似乎当时不是 nil。想法？如果您需要查看更多我的代码，请告诉我。

我也略微研究了 beginUpdates 和 endUpdates 方法，但在我看来，它们主要侧重于一次进行一些更改和用户交互性。我只想根据用户选择重新加载整个表(即，想根据当前用户登录反射(reflect)整个其他 SQL 选择字符串)。或者还有其他更好的方法吗？

提前致谢!

这是一段相当不错的代码:

#import "FirstViewController.h"
@interface FirstViewController ()
@end

@implementation FirstViewController
#import "FirstViewController.h"

@synthesize myTextView, myTableViewDataSource, myFetchedData, resultat, tablesAndChecks, tablesArr, checksArr, tablesToRequest,receivedData, receivedDataString, SQL, sqlStatementsArr, failedSqlStatementsArr, failedSqlStatementsCodeArr, dbloop1;



#pragma mark Table view methods
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
    return 1;
}

// Customize the number of rows in the table view.
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
    NSLog(@"Konfigurerar tableView"); //swedish for "Configuring tableView"
    if(myTableView.dataSource==nil){
        NSLog(@"datasource = nil");
    }else{
        NSLog(@"datasource != nil"); //This prints in log
    }
    NSLog(@"%d",[myTableViewDataSource count]); //prints "19" in log

    return [myTableViewDataSource count];
}

// Customize the appearance of table view cells.
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    NSLog(@"calling cellForRowAtIndexPath"); //This does NOT print in log

    static NSString *CellIdentifier = @"myCell";

    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil) {
        cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
    }

    // Set up the cell...
    cell.textLabel.font = [UIFont fontWithName:@"Helvetica" size:15];
    cell.textLabel.text = [NSString  stringWithFormat:@"Tabell %d: %@", [indexPath row], [myTableViewDataSource objectAtIndex:[indexPath row]]];

    return cell;
}



- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
    NSLog(@"connection did finish loading");

    //...
    //script that receives a long SQL-string from the server
    //and then updates the database with it goes here    
    //...

    //Ok, so now the database has updated correctly, and it's time 
    //to update the tableview so that it reflects the new data.
    //
    //Get data from database...
    NSMutableArray * tempArray = [[NSMutableArray alloc] initWithCapacity:0];

    if (sqlite3_open(dbpath, &contactDB) == SQLITE_OK)
    {
        NSLog(@"Databasen öppnad");
        NSString *beginSQL = [NSString stringWithFormat: @"SELECT name FROM sqlite_master WHERE type='table' ORDER BY name;"];
        const char *begin_stmt = [beginSQL UTF8String];
        sqlite3_prepare_v2(contactDB, begin_stmt, -1, &statement, NULL);
        while(sqlite3_step(statement) == SQLITE_ROW) {
            char *col1 = (char *)sqlite3_column_text(statement, 0);
            if (col1 !=NULL){
                [tempArray addObject:[NSString stringWithUTF8String: col1]];
            }
        }
        if (sqlite3_step(statement) == SQLITE_DONE)
        {
            NSLog(@"#####%s;   Done: %@", sqlite3_errmsg(nil), beginSQL);
        } else {
            NSLog(@"#####%s;   Error with string: %@; Errcode: %d Errmsg: %s", sqlite3_errmsg(nil), beginSQL, sqlite3_errcode(contactDB), sqlite3_errmsg(nil));
        }

        NSLog(@"%d", sqlite3_finalize(statement));
        sqlite3_close(contactDB);

        //update the datasource to the values of tempArray
        myTableViewDataSource = tempArray;

        //Some logging to see that the updated data is in the array... (which it is)
        NSLog(@"myTableViewDataSource count: %d",[myTableViewDataSource count]);

        for (i=0; i<[myTableViewDataSource count]; i++) {
            NSLog(@"%@",[myTableViewDataSource objectAtIndex:i]);
        }
    }

    //Finally, check so that myTableView isn't nil and can receive messages
    if(myTableView == nil){
        NSLog(@"NILCHECK mytableview is nil!");
    }else{
        NSLog(@"NILCHECK mytableview is NOT nil!"); //This is printed out to the log
    }

    //Reload data -> nothing happens...
    [myTableView reloadData];
}


- (void)fetchData
{
    //function that gets current checksums for all db tables on the server, compares them to the local database
    //and then requests an SQL-string from the server to update the tables that needs it.
    //I don't think this is relevant for my problem, and it runs fine anyways.

    //The last thing it does is setting up a NSURLConnection to communicate with 
    //the server (sending which tables to request via POST and then getting the SQL-string as the server response)

        NSURLConnection *theConnection=[[NSURLConnection alloc] initWithRequest:request delegate:self];
        if (theConnection) {
            //receivedData = [NSMutableData data];
            NSLog(@"ReceivedData är: %d", [receivedData length]);
        } else {
            NSLog(@"Connection Failed!");
        }

        //All done here, now the ReceivedData method takes over

    }
}

更新:

这是我的 viewDidLoad 方法:

- (void)viewDidLoad
{
    //creates database and fills "tempArray" with data

        NSLog(@"%d", sqlite3_finalize(statement));
        sqlite3_close(contactDB);

        myTableViewDataSource = tempArray;
        NSLog(@"myTableViewDataSource count: %d",[myTableViewDataSource count]);

        for (i=0; i<[myTableViewDataSource count]; i++) {
            NSLog(@"%@",[myTableViewDataSource objectAtIndex:i]);
        }

    }

    myTableView = [[UITableView alloc] initWithFrame:self.view.frame style:UITableViewStylePlain];
    myTableView.delegate = self;   //Added this after comment (1)
    myTableView.dataSource = self; //Added this after comment (2)
}

更新: 添加后:

myTableView.delegate = self;
myTableView.dataSource = self;

对于viewDidLoad，调用了tableView:numberOfRowsInSection:，dataSource不为nil，但是没有调用tableView:cellForRowAtIndexPath:，表没有更新。

更新 2: 这是我的头文件:

    //
//  FirstViewController.h
//  OHBSYS Storyboards
//
//  Created by David Forsberg on 2012-09-25.
//  Copyright (c) 2012 David Forsberg. All rights reserved.
//

#import <UIKit/UIKit.h>
#import <sqlite3.h>

@interface FirstViewController : UIViewController <UITableViewDataSource, UITableViewDelegate>{
    NSString *databasePath;
    sqlite3 *contactDB;

    UITextView *myTextView;
    UITableView *myTableView;

    NSMutableArray *myTableViewDataSource;

    NSMutableString * tableRowCount;
    NSMutableArray * dbloop1;

    //And a bunch of other variables here
}

@property (retain, nonatomic) IBOutlet UITextView *myTextView;
@property (nonatomic, retain) IBOutlet UITableView *myTableView;
@property (nonatomic, retain) IBOutlet NSMutableArray *myTableViewDataSource;

- (IBAction) fetchData;

@property (nonatomic) NSString * tableRowCount;
@property (nonatomic, retain) NSMutableArray * dbloop1;

//A bunch of other properties here as well

@end

更新 3:

我尝试使用断点检查值。

tableview 内的断点:numberofrowsinsection:

(lldb) po self.myTableView
(UITableView *) $0 = 0x0d13ca00 <UITableView: 0xd13ca00; frame = (0 20; 768 1004); clipsToBounds = YES; layer = <CALayer: 0x2a3d30>; contentOffset: {0, 0}>
(lldb) po self.myTableView.delegate
(objc_object *) $1 = 0x0ce99500 <FirstViewController: 0xce99500>
(lldb) po self.myTableView.dataSource
(objc_object *) $2 = 0x0ce99500 <FirstViewController: 0xce99500>
(lldb) po self.myTableViewDataSource
(NSMutableArray *) $3 = 0x0029fb20 <__NSArrayM 0x29fb20>(
CONTACTS,
sqlite_sequence
)

(lldb) 

数据库更新后的断点，就在调用 reloadData 之前:

(lldb) po self.myTableView
(UITableView *) $4 = 0x0d13ca00 <UITableView: 0xd13ca00; frame = (0 20; 768 1004); clipsToBounds = YES; layer = <CALayer: 0x2a3d30>; contentOffset: {0, 0}>
(lldb) po self.myTableView.delegate
(objc_object *) $5 = 0x0ce99500 <FirstViewController: 0xce99500>
(lldb) po self.myTableView.dataSource
(objc_object *) $6 = 0x0ce99500 <FirstViewController: 0xce99500>
(lldb) po self.myTableView.dataSource //(accidentally hit that twice)
(objc_object *) $7 = 0x0ce99500 <FirstViewController: 0xce99500>
(lldb) po self.myTableViewDataSource
(NSMutableArray *) $8 = 0x0ce6baa0 <__NSArrayM 0xce6baa0>(
CONTACTS,
meta_tablechecksums,
prot_multicoltest,
prot_multicoltest_4,
prot_multicoltest_4_desc,
prot_multicoltest_desc,
sqlite_sequence,
superadmin_filefolders,
superadmin_files,
superadmin_imagefolders,
superadmin_images,
sys_customers,
sys_fieldlooks,
sys_fieldtypes,
sys_formtables,
sys_pages,
sys_subpages,
sys_userroles,
sys_users
)

(lldb) 

断点在reloadData行:

(lldb) po self.myTableView
(UITableView *) $9 = 0x0d13ca00 <UITableView: 0xd13ca00; frame = (0 20; 768 1004); clipsToBounds = YES; layer = <CALayer: 0x2a3d30>; contentOffset: {0, 0}>
(lldb) po self.myTableView.delegate
(objc_object *) $10 = 0x0ce99500 <FirstViewController: 0xce99500>
(lldb) po self.myTableView.dataSource
(objc_object *) $11 = 0x0ce99500 <FirstViewController: 0xce99500>
(lldb) po self.myTableViewDataSource
(NSMutableArray *) $12 = 0x0ce6baa0 <__NSArrayM 0xce6baa0>(
CONTACTS,
meta_tablechecksums,
prot_multicoltest,
prot_multicoltest_4,
prot_multicoltest_4_desc,
prot_multicoltest_desc,
sqlite_sequence,
superadmin_filefolders,
superadmin_files,
superadmin_imagefolders,
superadmin_images,
sys_customers,
sys_fieldlooks,
sys_fieldtypes,
sys_formtables,
sys_pages,
sys_subpages,
sys_userroles,
sys_users
)

(lldb) 

tableview 内的断点:numberofrowsinsection:更新数据库并运行 reloadData 命令后:

(lldb) po self.myTableView
(UITableView *) $13 = 0x0d13ca00 <UITableView: 0xd13ca00; frame = (0 20; 768 1004); clipsToBounds = YES; layer = <CALayer: 0x2a3d30>; contentOffset: {0, 0}>
(lldb) po self.myTableView.delegate
(objc_object *) $14 = 0x0ce99500 <FirstViewController: 0xce99500>
(lldb) po self.myTableView.dataSource
(objc_object *) $15 = 0x0ce99500 <FirstViewController: 0xce99500>
(lldb) po self.myTableViewDataSource
(NSMutableArray *) $16 = 0x0ce6baa0 <__NSArrayM 0xce6baa0>(
CONTACTS,
meta_tablechecksums,
prot_multicoltest,
prot_multicoltest_4,
prot_multicoltest_4_desc,
prot_multicoltest_desc,
sqlite_sequence,
superadmin_filefolders,
superadmin_files,
superadmin_imagefolders,
superadmin_images,
sys_customers,
sys_fieldlooks,
sys_fieldtypes,
sys_formtables,
sys_pages,
sys_subpages,
sys_userroles,
sys_users
)

(lldb) 

Answer 1

我没有看到正在合成的 myTableView。 在执行 reloadData 时，还会调用 tableView 数据源方法吗？

如果没有，请仔细检查并确认 myTableView 委托(delegate)设置正确。 如果您已将 Table 正确连接到 Nib 并且您有一个 socket ，您也可以在代码中设置它，即在 viewDidLoad 方法中，通过设置:

myTableView.delegate = self;