UITableView 重新加载 - Xcode 5

Posted 2023-03-08

【中文标题】UITableView 重新加载 - Xcode 5

【英文标题】：UITableView reload - Xcode 5

【发布时间】：2014-01-07 21:03:52

【问题描述】：

我正在使用嵌入在导航控制器中的 UITableView（带有表格单元）。应用启动时，会读取 SQLite3 数据库中的数据并将其添加到表格单元格中。

我制作了一个按钮（在导航栏上），它将引导用户进入一个他可以输入新数据的屏幕。当用户点击导航控制器自动添加的按钮“返回”时，就会发生“保存”。

当用户返回起始页时，数据不会被重新加载，因此新条目在重新启动应用程序之前是不可见的。

当数据返回视图时刷新数据的最佳方式是什么？

#import "lucidViewController.h"
#import "lucidCell.h"

@interface lucidViewController () 


@end

@implementation lucidViewController
@synthesize titleData,descrData,idKeyData;

- (void)viewDidLoad 
    self.myTableView.dataSource = self;
    self.myTableView.delegate = self;

    [self openDB];
    [self createTable:@"dreams" withField1:@"idKey" withField2:@"title" withField3:@"description"];

    titleData = [[NSMutableArray alloc] init];
    descrData = [[NSMutableArray alloc] init];
    idKeyData = [[NSMutableArray alloc] init];

    [self loadData];

    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.


- (void) loadData 
    NSString *sql = [NSString stringWithFormat:@"SELECT * FROM dreams"];
    sqlite3_stmt *statement;

    if (sqlite3_prepare_v2(dataBase, [sql UTF8String], -1, &statement, nil) == SQLITE_OK) 
        while (sqlite3_step(statement) == SQLITE_ROW) 
            char *field1 = (char *) sqlite3_column_text(statement, 0);
            NSString *field1Str = [[NSString alloc]initWithUTF8String:field1];

            char *field2 = (char *) sqlite3_column_text(statement, 1);
            NSString *field2Str = [[NSString alloc]initWithUTF8String:field2];

            char *field3 = (char *) sqlite3_column_text(statement, 2);
            NSString *field3Str = [[NSString alloc]initWithUTF8String:field3];

            [idKeyData addObject:field1Str];
            [titleData addObject:field2Str];
            [descrData addObject:field3Str];
        
    


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


- (NSString *) filePath 
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    return [[paths objectAtIndex:0] stringByAppendingPathComponent:@"lucid.sql"];


- (void) openDB 
    if (sqlite3_open([[self filePath] UTF8String], &dataBase) != SQLITE_OK) 
        sqlite3_close(dataBase);
        NSAssert(0, @"Database kan niet geopend worden");
     else 
        NSLog(@"Database is geopend!");
    


- (void) createTable:(NSString *)tableName withField1:(NSString *)field1 withField2:(NSString *)field2 withField3:(NSString *)field3 
    char *error;
    NSString *sqlStatement = [NSString stringWithFormat:
                              @"CREATE TABLE IF NOT EXISTS '%@'('%@' TEXT PRIMARY KEY, '%@' TEXT, '%@' TEXT);",tableName,field1,field2,field3];
    if (sqlite3_exec(dataBase, [sqlStatement UTF8String], NULL, NULL, &error) != SQLITE_OK) 
        sqlite3_close(dataBase);
        NSLog(@"Table kan niet aangemaakt worden..");
     else 
        NSLog(@"Table aangemaakt!");
    


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


- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section 
    return [titleData count];


- (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section 
    return 0;


- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath 
    static NSString *CellIdentifier = @"Cell";
    lucidCell *Cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (!Cell) 
        Cell = [[lucidCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
    
    Cell.descrLabel.text = [self.descrData objectAtIndex:indexPath.row];
    Cell.titleLabel.text = [self.titleData objectAtIndex:indexPath.row];
    return Cell;

@end

此处添加新数据：

#import "newViewController.h"

@interface newViewController ()

@end

@implementation newViewController
@synthesize addNewDream;

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


- (void)viewDidLoad 
    [self openDB];
    [self genRandStringLength:20];
    [super viewDidLoad];
    // Do any additional setup after loading the view.


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


- (NSString *) filePath 
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    return [[paths objectAtIndex:0] stringByAppendingPathComponent:@"lucid.sql"];


- (void) openDB 
    if (sqlite3_open([[self filePath] UTF8String], &dataBase) != SQLITE_OK) 
        sqlite3_close(dataBase);
        NSAssert(0, @"Database kan niet geopend worden");
     else 
        NSLog(@"Database is geopend!");
    


-(NSString *) genRandStringLength: (int) len 
    NSString *letters = @"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
    NSMutableString *randomString = [NSMutableString stringWithCapacity: len];

    for (int i=0; i<len; i++) 
        [randomString appendFormat: @"%C", [letters characterAtIndex: arc4random() % [letters length]]];
    
    return randomString;


- (void) viewWillDisappear:(BOOL)animated 
    NSString *dreamText = addNewDream.text;
    NSString *idKey = [self genRandStringLength:25];
    NSDate *myDate = [NSDate date];
    NSDateFormatter *df = [NSDateFormatter new];
    [df setDateFormat:@"dd/MM/yyyy, hh:mm"];
    NSString *title = [df stringFromDate:myDate];

    if (![dreamText isEqualToString:@""])
        NSString *statement = [NSString stringWithFormat:@"INSERT INTO dreams ('idKey','title','description') VALUES ('%@','%@','%@')",idKey,title,dreamText];
        char *error;
        if (sqlite3_exec(dataBase, [statement UTF8String], NULL, NULL, &error) != SQLITE_OK) 
            sqlite3_close(dataBase);
            NSAssert(0, @"Kan niet wegschrijven naar tabel");
         else 
            NSLog(@"Table write succesvol!");
        
     else 
        NSLog(@"Geen nieuwe droom ingevuld..");
    

【参考方案1】：

您可以像这样在 viewDidAppear 方法中刷新表格视图和数据模型：

-(void)viewDidAppear:(BOOL)animated 

   [super viewDidAppear:animated];    

   [self loadData]; 
   [self.myTableView reload]; 

【讨论】：

太棒了！只有每次都将数据添加到我的数组中，所以我的列表中出现了重复的条目。我应该每次都清空数组还是有其他方法？

通过使数组为空来修复它。谢谢。