我有一个表格视图,我刚刚实现了一个类,该类可以帮助我重新排列单元格,例如表格视图委托附带的常规移动单元格方法。
现在,在对单元格重新排序之后,我需要将保存单元格对象的数组更改为新的顺序...我该怎么做?
这是我重新排序单元格的方法:
- (void)moveTableView:(FMMoveTableView *)tableView moveRowFromIndexPath:(NSIndexPath *)fromIndexPath toIndexPath:(NSIndexPath *)toIndexPath { NSArray
}
我有一个coreDataStack类,该类负责处理所有核心数据(创建singelton),它看起来像这样:
#import "CoreDataStack.h"
@implementation CoreDataStack
#pragma mark - Core Data stack
@synthesize managedObjectContext = _managedObjectContext;
@synthesize managedObjectModel = _managedObjectModel;
@synthesize persistentStoreCoordinator = _persistentStoreCoordinator;
+ (instancetype)defaultStack {
static CoreDataStack *defaultStack;
static dispatch_once_t onceTocken;
dispatch_once (&onceTocken, ^{
defaultStack = [[self alloc] init];
});
return defaultStack;
}
- (NSURL *)applicationDocumentsDirectory {
// The directory the application uses to store the Core Data store file. This code uses a directory named "digitalCrown.Lister" in the application's documents directory.
return [[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask] lastObject];
}
- (NSManagedObjectModel *)managedObjectModel {
// The managed object model for the application. It is a fatal error for the application not to be able to find and load its model.
if (_managedObjectModel != nil) {
return _managedObjectModel;
}
NSURL *modelURL = [[NSBundle mainBundle] URLForResource:@"Lister" withExtension:@"momd"];
_managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL];
return _managedObjectModel;
}
- (NSPersistentStoreCoordinator *)persistentStoreCoordinator {
// The persistent store coordinator for the application. This implementation creates and return a coordinator, having added the store for the application to it.
if (_persistentStoreCoordinator != nil) {
return _persistentStoreCoordinator;
}
// Create the coordinator and store
_persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];
NSURL *storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:@"Lister.sqlite"];
NSError *error = nil;
NSString *failureReason = @"There was an error creating or loading the application's saved data.";
if (![_persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&error]) {
// Report any error we got.
NSMutableDictionary *dict = [NSMutableDictionary dictionary];
dict[NSLocalizedDescriptionKey] = @"Failed to initialize the application's saved data";
dict[NSLocalizedFailureReasonErrorKey] = failureReason;
dict[NSUnderlyingErrorKey] = error;
error = [NSError errorWithDomain:@"YOUR_ERROR_DOMAIN" code:9999 userInfo:dict];
// Replace this with code to handle the error appropriately.
// abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
abort();
}
return _persistentStoreCoordinator;
}
- (NSManagedObjectContext *)managedObjectContext {
// Returns the managed object context for the application (which is already bound to the persistent store coordinator for the application.)
if (_managedObjectContext != nil) {
return _managedObjectContext;
}
NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator];
if (!coordinator) {
return nil;
}
_managedObjectContext = [[NSManagedObjectContext alloc] init];
[_managedObjectContext setPersistentStoreCoordinator:coordinator];
return _managedObjectContext;
}
#pragma mark - Core Data Saving support
- (void)saveContext {
NSManagedObjectContext *managedObjectContext = self.managedObjectContext;
if (managedObjectContext != nil) {
NSError *error = nil;
if ([managedObjectContext hasChanges] && ![managedObjectContext save:&error]) {
// Replace this implementation with code to handle the error appropriately.
// abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
abort();
}
}
}
@end
每当我将新对象添加到核心数据时,我都会这样做:
- (void)insertTeget {
CoreDataStack *stack = [CoreDataStack defaultStack];
Target *target = [NSEntityDescription insertNewObjectForEntityForName:@"Target" inManagedObjectContext:stack.managedObjectContext];
if (self.myTextView.text != nil) {
target.body = self.myTextView.text;
target.time = [NSDate date];
}
[stack saveContext];
}
在表视图中,当我获取数据时,我这样做:
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *cellIdentifier = @"StackTableViewCell";
Target *target = [self.fetchedResultController objectAtIndexPath:indexPath];
StackTableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:cellIdentifier];
if (!cell)
{
NSArray *topLevelObjects = [[NSBundle mainBundle] loadNibNamed:@"StackTableViewCell" owner:self options:nil];
cell = [topLevelObjects objectAtIndex:0];
}
cell.cellLabel.text = target.body;
cell.cellLabel.font = [UIFont fontWithName:@"Candara-Bold" size:20];
cell.showsReorderControl = YES;
// Configure the cell...
return cell;
}
这是我在表视图控制器类中的fetchresultconroller / fetch请求配置:
- (NSFetchRequest *)targetsFetchRequest {
NSFetchRequest *fetchRequest = [NSFetchRequest fetchRequestWithEntityName:@"Target"];
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"time" ascending:YES];
NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];
[fetchRequest setSortDescriptors:sortDescriptors];
return fetchRequest;
}
- (NSFetchedResultsController *)fetchedResultController {
if (_fetchedResultController != nil) {
return _fetchedResultController;
}
CoreDataStack *stack = [CoreDataStack defaultStack];
NSFetchRequest *fetchRequest = [self targetsFetchRequest];
_fetchedResultController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:stack.managedObjectContext sectionNameKeyPath:nil cacheName:nil];
_fetchedResultController.delegate = self;
return _fetchedResultController;
}
我要完成的工作是,每当用户创建目标对象时,它将到达数组的末尾(因此它将像一个队列),并且如果用户移动了单元格,那么我需要更改数组的顺序。数据库...
移动细胞方法:
- (void)moveTableView:(FMMoveTableView *)tableView moveRowFromIndexPath:(NSIndexPath *)fromIndexPath toIndexPath:(NSIndexPath *)toIndexPath {
int start = 0;
int end = 0;
if (fromIndexPath.row > toIndexPath.row) {
start = (int)fromIndexPath.row;
end = (int)toIndexPath.row;
} else {
start = (int)toIndexPath.row;
end = (int)fromIndexPath.row;
}
for (int i = start; i <= end; ++i) {
Target *target = [self.fetchedResultController objectAtIndexPath:[NSIndexPath indexPathForRow:i inSection:0]];
[target setOrder:@(i)];
}
[[CoreDataStack defaultStack] saveContext];
// a test to see if the order is changed
[self.fetchedResultController performFetch:nil];
NSArray *arr = [self.fetchedResultController fetchedObjects];
for (int i=0; i<arr.count; i++) {
Target *ta = [arr objectAtIndex:i];
NSLog(@"%@",ta.body);
}
}
日志:
2015-04-14 10:29:13.405 Lister[3163:477453] One
2015-04-14 10:29:13.406 Lister[3163:477453] Two
2015-04-14 10:29:13.406 Lister[3163:477453] Three
2015-04-14 10:29:13.407 Lister[3163:477453] Four
2015-04-14 10:29:13.407 Lister[3163:477453] Five
2015-04-14 10:29:21.070 Lister[3163:477453]
2015-04-14 10:29:21.071 Lister[3163:477453] One
2015-04-14 10:29:21.071 Lister[3163:477453] Two
2015-04-14 10:29:21.071 Lister[3163:477453] Three
2015-04-14 10:29:21.072 Lister[3163:477453] Four
2015-04-14 10:29:21.072 Lister[3163:477453] Five
2015-04-14 10:29:25.037 Lister[3163:477453]
2015-04-14 10:29:25.039 Lister[3163:477453] One
2015-04-14 10:29:25.039 Lister[3163:477453] Two
2015-04-14 10:29:25.040 Lister[3163:477453] Three
2015-04-14 10:29:25.040 Lister[3163:477453] Four
2015-04-14 10:29:25.041 Lister[3163:477453] Five
另外,如果将带有标签“一”的单元格移动到带有标签“二”的单元格的索引,则单元格的标签现在变得很奇怪,因此“一”的标签将变为“二”。因此,我想到了2个单元格具有相同标签的情况。
那么最简单的解决方案是
Target
实体添加一个属性,说出其order
类型Integer32
。创建和插入新对象
每当创建新Target
对象时,都首先使用sortDescriptor
具有key@"order"
和的键从数据库中获取现有对象ascending=YES
。取得此提取数组的最后一个对象并检查其顺序。现在,在您的新Target
对象中,递增顺序并将其插入数据库。如果获取的数组返回0个对象,则设置order=@(0)
。
- (void)insertTeget {
CoreDataStack *stack = [CoreDataStack defaultStack];
//Fetching objects from database
NSFetchRequest *fetchRequest = [NSFetchRequest fetchRequestWithEntityName:@"Target"];
NSSortDescriptor *sortDescriptor = [NSSortDescriptor sortDescriptorWithKey:@"order" ascending:YES];
[fetchRequest setSortDescriptors:@[sortDescriptor]];
NSArray *existingObjects = [stack.managedObjectContext executeFetchRequest:fetchRequest error:nil];
//Creating new object
Target *target = [NSEntityDescription insertNewObjectForEntityForName:@"Target" inManagedObjectContext:stack.managedObjectContext];
if (self.myTextView.text != nil) {
target.body = self.myTextView.text;
target.order = @([(Target *)existingObjects.lastObject order].integerValue + 1);
}
[stack saveContext];
}
NSFetchedResultsController
sortDescriptor
。取自您的代码
- (NSFetchRequest *)targetsFetchRequest {
NSFetchRequest *fetchRequest = [NSFetchRequest fetchRequestWithEntityName:@"Target"];
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"order" ascending:YES];
NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];
[fetchRequest setSortDescriptors:sortDescriptors];
return fetchRequest;
}
- (NSFetchedResultsController *)fetchedResultController {
if (_fetchedResultController != nil) {
return _fetchedResultController;
}
CoreDataStack *stack = [CoreDataStack defaultStack];
NSFetchRequest *fetchRequest = [self targetsFetchRequest];
_fetchedResultController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:stack.managedObjectContext sectionNameKeyPath:nil cacheName:nil];
_fetchedResultController.delegate = self;
return _fetchedResultController;
}
重新排列单元
现在,当您在表格视图中重新排列单元格时,只需要运行一个for循环并更新其顺序即可。您只需要更新order
两个indexPath之间的对象。
- (void)moveTableView:(FMMoveTableView *)tableView moveRowFromIndexPath:(NSIndexPath *)fromIndexPath toIndexPath:(NSIndexPath *)toIndexPath {
int start = 0;
int end = 0;
if (fromIndexPath.row > toIndexPath.row) {
start = fromIndexPath.row;
end = toIndexPath.row;
} else {
start = toIndexPath.row;
end = fromIndexPath.row;
}
for (int i = start; i <= end; ++i) {
Target *target = [self.fetchedResultsController objectAtIndexPath:[NSIndexPath indexPathForRow:i inSection:0]];
[target setOrder:@(i)];
}
[[CoreDataStack defaultStack] saveContext];
}
注意:以上解决方案假定您order
从0开始。
在创建和插入新Target
对象时,需要实现NSFetchedResultsController
委托方法以为这些对象添加相应的行。由于我们已经定义了sortDescriptor
,因此将在的末尾添加新行tableView
。
- (void)controllerWillChangeContent:(NSFetchedResultsController *)controller {
[self.tableView beginUpdates];
}
- (void)controller:(NSFetchedResultsController *)controller didChangeSection:(id <NSFetchedResultsSectionInfo>)sectionInfo
atIndex:(NSUInteger)sectionIndex forChangeType:(NSFetchedResultsChangeType)type {
switch(type) {
case NSFetchedResultsChangeInsert:
[self.tableView insertSections:[NSIndexSet indexSetWithIndex:sectionIndex]
withRowAnimation:UITableViewRowAnimationFade];
break;
}
}
- (void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject
atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type
newIndexPath:(NSIndexPath *)newIndexPath {
UITableView *tableView = self.tableView;
switch(type) {
case NSFetchedResultsChangeInsert:
[tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath]
withRowAnimation:UITableViewRowAnimationFade];
break;
case NSFetchedResultsChangeUpdate:
break;
case NSFetchedResultsChangeMove:
[tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath]
withRowAnimation:UITableViewRowAnimationFade];
[tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath]
withRowAnimation:UITableViewRowAnimationFade];
break;
}
}
- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller {
[self.tableView endUpdates];
}
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我来说两句