第二步：为项目添加 CoreData.framework 框架，然后在 .pch 中加入 #import <coredata/coredata.h>
第三步：在 app delegate 中定义 core data 的相关对象（同时完成它们的初始化工作）
.h 文件：
#import <coredata/coredata.h>
@private
NSManagedObjectModel *managedObjectModel
NSManagedObjectContext *managedObjectContext
NSPersistentStoreCoordinator *persistentStoreCoordinator
@property (nonatomic, retain, readonly) NSManagedObjectModel *managedObjectModel
@property (nonatomic, retain, readonly) NSManagedObjectContext *managedObjectContext
@property (nonatomic, retain, readonly) NSPersistentStoreCoordinator *persistentStoreCoordinator
- (NSString*) applicationDocumentsDirectory
- (void) saveContext
.m 文件：
@synthesize managedObjectModel
@synthesize managedObjectContext
@synthesize persistentStoreCoordinator
- (void)dealloc {
[managedObjectModel release]
[managedObjectContext release]
[persistentStoreCoordinator release]
[super dealloc]
}
- (NSString*)applicationDocumentsDirectory
{
//return [[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask] lastObject]
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)
NSString *basePath = ([paths count] >0) ? [paths objectAtIndex:0] : nil
return basePath
//return [NSURL URLWithString:basePath]
}
- (void)saveContext{
NSError *error = nil
NSManagedObjectContext *objectContext = self.managedObjectContext
if (objectContext != nil)
{
if ([objectContext hasChanges] &&![objectContext save:&error])
{
NSLog(@"Unresolved error %@, %@", error, [error userInfo])
abort()
}
}
}
- (NSManagedObjectContext *)managedObjectContext
{
if (managedObjectContext != nil) {
return managedObjectContext
}
NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator]
if (coordinator != nil) {
managedObjectContext = [[NSManagedObjectContext alloc] init]
[managedObjectContext setPersistentStoreCoordinator:coordinator]
}
return managedObjectContext
}
- (NSManagedObjectModel *)managedObjectModel
{
if (managedObjectModel != nil) {
return managedObjectModel
}
//从本地所有 xcdatamodel 文件中获得这个 CoreData 的数据模板
managedObjectModel = [[NSManagedObjectModel mergedModelFromBundles:nil] retain]
return managedObjectModel
}
- (NSPersistentStoreCoordinator *)persistentStoreCoordinator
{
if (persistentStoreCoordinator != nil) {
return persistentStoreCoordinator
}
//数据库名为TestDB.sqlite
NSURL *storeUrl = [NSURL fileURLWithPath:[[self applicationDocumentsDirectory] stringByAppendingPathComponent:@"TestDB.sqlite"]]
NSError *error
persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]]
if (![persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nilURL:storeUrl options:nil error:&error]) {
NSAssert(0, @"persistentStoreCoordinator init failed!")
}
return persistentStoreCoordinator
}
- (void)applicationWillTerminate:(UIApplication *)application
{
NSError *error
if (managedObjectContext != nil) {
if ([managedObjectContext hasChanges] &&![managedObjectContext save:&error]) {
NSAssert(0, @"save changes failed when terminage application!")
}
}
}
第四步：在相关的 viewcontroller 中 *** 作数据，基本的 core data *** 作代码如下：
NSError *error
testSQLiteAppDelegate *app = (testSQLiteAppDelegate*)[[UIApplication sharedApplication] delegate]
NSManagedObjectContext *context = app.managedObjectContext
//1、插入
NSManagedObject *newManagedObject = nil
newManagedObject = [NSEntityDescription insertNewObjectForEntityForName:@"Entity1" inManagedObjectContext:context]
[newManagedObject setValue:[NSNumber numberWithInt:1] forKey:@"id"]
[newManagedObject setValue:@"i love you" forKey:@"name"]
if (![context save:&error]){
NSLog (@"The error is: %@", [error userInfo])
}
else
{
NSLog (@"The newManagedObject's id is: %@", [newManagedObject valueForKey:@"id"])
}
//2、查询
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init]
NSEntityDescription *entity = [NSEntityDescription entityForName:@"Entity1" inManagedObjectContext:context]
NSSortDescriptor *sortDescriptor1 = [[NSSortDescriptor alloc] initWithKey:@"id" ascending:YES]
NSSortDescriptor *sortDescriptor2 = [[NSSortDescriptor alloc] initWithKey:@"name" ascending:YES]
NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor1, sortDescriptor2, nil]
[fetchRequest setSortDescriptors:sortDescriptors]
[fetchRequest setEntity:entity]
[fetchRequest setFetchBatchSize:20]
NSArray *objects = [context executeFetchRequest: fetchRequest error:&error]
if (objects == nil)
{
NSLog(@"There was an error!")
}
else {
for (NSManagedObject *oneObject in objects)
{
NSLog(@"%@",[oneObject valueForKey:@"name"])
}
}
//3、删除
[context deleteObject:[objects objectAtIndex:0]]
if (![context save:&error]) {
exit(-1)
}
这里更详细的补充一点关于 core data 的 *** 作代码：
1、条件过滤:选择 cid=1 的数据
- (NSFetchedResultsController*) fetchedResultsController
{
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"cid=1"]
[fetchRequest setPredicate:predicate]
}
2、通用代码，在 viewcontroller 里面会用到：
TestViewController.h 的代码：
@interface TestViewController : UITableViewController <NSFetchedResultsControllerDelegate>
{
NSFetchedResultsController *fetchedResultsController
NSManagedObjectContext *managedObjectContext
}
@property (nonatomic, retain) NSFetchedResultsController *fetchedResultsController
@property (nonatomic, retain) NSManagedObjectContext *managedObjectContext
- (void)configureCell:(UITableViewCell *)cell withCategory:(Category *)category
@end
TestViewController.m 的代码：
-(NSFetchedResultsController *)fetchedResultsController
{
if (fetchedResultsController != nil)
{
return fetchedResultsController
}
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init]
NSEntityDescription *entity = [NSEntityDescription entityForName:@"Category" inManagedObjectContext:managedObjectContext]
[fetchRequest setEntity:entity]
NSSortDescriptor *nameDescriptor = [[NSSortDescriptor alloc] initWithKey:@"name" ascending:YES]
NSArray *arraySortDescriptor = [[NSArray alloc] initWithObjects:nameDescriptor, nil]
[fetchRequest setSortDescriptors:arraySortDescriptor]
NSPredicate *predicate = [NSPredicate predicateWithFormat:cidString]
[fetchRequest setPredicate:predicate]
NSFetchedResultsController *frController = [[NSFetchedResultsController alloc]
initWithFetchRequest:fetchRequest managedObjectContext:managedObjectContext sectionNameKeyPath:@"name" cacheName:@"Root"]
frController.delegate = self
self.fetchedResultsController = frController
[frController release]
[fetchRequest release]
[nameDescriptor release]
return fetchedResultsController
}
- (void)controllerWillChangeContent:(NSFetchedResultsController *)
{
[self.tableView beginUpdates]
}
- (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 NSFetchedResultsChangeDelete:
[tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade]
break
case NSFetchedResultsChangeMove:
[tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade]
[tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath] withRowAnimation:UITableViewRowAnimationFade]
break
case NSFetchedResultsChangeUpdate:
[self configureCell:[tableView cellForRowAtIndexPath:indexPath] withCategory:anObject]
break
default:
break
}
}
- (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
case NSFetchedResultsChangeDelete:
[self.tableView deleteSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade]
break
}
}
- (void) controllerDidChangeContent:(NSFetchedResultsController *)controller
{
[self.tableView endUpdates]
}
第一种：通过人为的办法改变view.transform的属性。具体办法：
view.transform一般是View的旋转，拉伸移动等属性，类似view.layer.transform，区别在于 View.transform是二维的，也就是使用仿射的办法通常就是带有前缀CGAffineTransform的类（可以到api文档里面搜索这个前 缀的所有类），而view.layer.transform可以在3D模式下面的变化，通常使用的都是前缀为CATransform3D的类。
这里要记住一点，当你改变过一个view.transform属性或者view.layer.transform的时候需要恢复默认状态的话，记得先把他 们重置可以使用view.transform = CGAffineTransformIdentity，或者view.layer.transform = CATransform3DIdentity，假设你一直不断的改变一个view.transform的属性，而每次改变之前没有重置的话，你会发现后来 的改变和你想要的发生变化了，不是你真正想要的结果。
好了，上面介绍了旋转的属性，接下来就是关键了。官方提供了一个办法就是查看当前电池条的状态UIInterfaceOrientation orientation = [UIApplication sharedApplication].statusBarOrientation通过这个办法，你可以知道当前屏幕的电池条的显示方向，而且你还可以 强制设置他的显示方向，通过设置这个属性就OK了，可以选择是否动画改变电池条方向。有了这两个那我们就可以任意的改变我们想要的显示方式了。
1.获取当前电池条的方向UIInterfaceOrientation orientation = [UIApplication sharedApplication].statusBarOrientation
2.获取当前屏幕的大小CGRect frame = [UIScreen mainScreen].applicationFrame
3.设置我们的View的中心点
CGPoint center = CGPointMake(frame.origin.x + ceil(frame.size.width/2), frame.origin.y + ceil(frame.size.height/2))
4.根据当前电池条的方向，获取需要旋转的角度的大小。通常
if (orientation == UIInterfaceOrientationLandscapeLeft) {
return CGAffineTransformMakeRotation(M_PI*1.5)
} else if (orientation == UIInterfaceOrientationLandscapeRight) {
return CGAffineTransformMakeRotation(M_PI/2)
} else if (orientation == UIInterfaceOrientationPortraitUpsideDown) {
return CGAffineTransformMakeRotation(-M_PI)
} else {
return CGAffineTransformIdentity
}
5.可以动画的改变我们view的显示方式了
[[UIApplication sharedApplication] setStatusBarOrientation:UIDeviceOrientationLandscapeRight animated:YES]
CGFloat duration = [UIApplication sharedApplication].statusBarOrientationAnimationDuration（获取当前电池条动画改变的时间）
[UIView beginAnimations:nil context:nil]
[UIView setAnimationDuration:duration]
//在这里设置view.transform需要匹配的旋转角度的大小就可以了。
[UIView commitAnimations]
第二种：通过setOrientation:的办法强制性的旋转到一个特定的方向。
注意：apple在3.0以后都不支持这个办法了，这个办法已经成为了私有的了，但是要跳过App Stroe的审核，需要一点巧妙的办法。
不要直接调用[[UIDevice currentDevice] setOrientation: UIInterfaceOrientationLandscapeRight]这样的办法来强制性的横屏，这样导致你的程序是很难通过App Store审核的。但是你可以选择使用performSelector的办法来调用它。具体就几行代码如下：
//强制横屏
if ([[UIDevice currentDevice] respondsToSelector:@selector(setOrientation:)]) {
[[UIDevice currentDevice] performSelector:@selector(setOrientation:)
withObject:(id)UIInterfaceOrientationLandscapeRight]
}
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