作为初学者,我在 iCloud 上苦苦挣扎。有一些示例,但它们通常非常详细(在开发者论坛上有一个用于 iCloud 和 CoreData 的大量示例)。苹果文档还可以,但我仍然看不到大局。所以请耐心等待,其中一些问题非常基础,但可能很容易回答。
上下文:我有一个非常简单的 iCloud 应用程序正在运行(下面的完整示例代码)。只有一个 UITextView 显示给用户,他/她的输入保存在一个名为 text.txt 的文件中。
txt 文件被推送到云端并可供所有设备使用。完美运行,但是:
主要问题:不使用 iCloud 的用户怎么办?
当我启动我的应用程序(见下面的代码)时,我会检查用户是否启用了 iCloud。如果启用了 iCloud,一切都很好。该应用程序继续并在云中查找 text.txt。如果找到,它将加载并显示给用户。如果在云中找不到 text.txt,它将简单地创建一个新的 text.txt 并将其显示给用户。
如果用户没有启用 iCloud,什么都不会发生。如何让非 iCloud 用户仍然可以使用我的文本应用程序?还是我只是忽略它们?我需要为非 iCloud 用户编写单独的函数吗?即,我只需从文档文件夹中加载 text.txt 的功能?
苹果写道:
对待 iCloud 中的文件就像对待应用沙箱中的所有其他文件一样。
但是,就我而言,不再有“正常”的应用程序沙箱。它在云端。还是我总是先从磁盘加载我的 text.txt,然后再通过 iCloud 检查是否有更新的内容?
相关问题:文件结构 - 沙盒与云
也许我的主要问题是对 iCloud 应该如何工作的根本误解。当我创建一个 UIDocument 的新实例时,我将不得不覆盖两个方法。首先- (BOOL)loadFromContents:(id)contents ofType:(NSString *)typeName error:(NSError **)outError
从云中获取文件,然后-(id)contentsForType:(NSString *)typeName error:(NSError **)outError
将文件获取到云中。
我是否必须合并单独的函数,这些函数也会将 text.txt 的本地副本保存到我的沙箱中?这对非 iCloud 用户有用吗?据我了解 iCloud,它会自动保存 text.txt 的本地副本。因此,我不需要将任何内容保存到我的应用程序的“旧”沙箱中(即,它曾经在旧的、前 iCloud 时代)。现在,我的沙箱完全是空的,但我不知道这是否正确。我应该在其中保留另一份 text.txt 吗?这感觉就像把我的数据结构弄得一团糟……因为云中有一个 text.txt,我设备上的 iCloud 沙箱中有一个(即使我离线也可以工作),第三个在旧的沙箱中我的应用...
我的代码:一个简单的 iCloud 示例代码
这大致基于我在开发者论坛和 WWDC 会议视频中找到的示例。我把它剥离到最低限度。我不确定我的 MVC 结构是否良好。该模型位于 AppDelegate 中,这并不理想。欢迎提出任何使它变得更好的建议。
编辑:我试图提取主要问题并将其发布 [here]。4
概述:
从云端加载 text.txt 的最重要部分:
// AppDelegate.h
// iCloudText
#import <UIKit/UIKit.h>
@class ViewController;
@class MyTextDocument;
@interface AppDelegate : UIResponder <UIApplicationDelegate> {
NSMetadataQuery *_query;
}
@property (strong, nonatomic) UIWindow *window;
@property (strong, nonatomic) ViewController *viewController;
@property (strong, nonatomic) MyTextDocument *document;
@end
// AppDelegate.m
// iCloudText
#import "AppDelegate.h"
#import "MyTextDocument.h"
#import "ViewController.h"
@implementation AppDelegate
@synthesize window = _window;
@synthesize viewController = _viewController;
@synthesize document = _document;
- (void)dealloc
{
[_window release];
[_viewController release];
[super dealloc];
}
- (void)loadData:(NSMetadataQuery *)query {
// (4) iCloud: the heart of the load mechanism: if texts was found, open it and put it into _document; if not create it an then put it into _document
if ([query resultCount] == 1) {
// found the file in iCloud
NSMetadataItem *item = [query resultAtIndex:0];
NSURL *url = [item valueForAttribute:NSMetadataItemURLKey];
MyTextDocument *doc = [[MyTextDocument alloc] initWithFileURL:url];
//_document = doc;
doc.delegate = self.viewController;
self.viewController.document = doc;
[doc openWithCompletionHandler:^(BOOL success) {
if (success) {
NSLog(@"AppDelegate: existing document opened from iCloud");
} else {
NSLog(@"AppDelegate: existing document failed to open from iCloud");
}
}];
} else {
// Nothing in iCloud: create a container for file and give it URL
NSLog(@"AppDelegate: ocument not found in iCloud.");
NSURL *ubiq = [[NSFileManager defaultManager] URLForUbiquityContainerIdentifier:nil];
NSURL *ubiquitousPackage = [[ubiq URLByAppendingPathComponent:@"Documents"] URLByAppendingPathComponent:@"text.txt"];
MyTextDocument *doc = [[MyTextDocument alloc] initWithFileURL:ubiquitousPackage];
//_document = doc;
doc.delegate = self.viewController;
self.viewController.document = doc;
[doc saveToURL:[doc fileURL] forSaveOperation:UIDocumentSaveForCreating completionHandler:^(BOOL success) {
NSLog(@"AppDelegate: new document save to iCloud");
[doc openWithCompletionHandler:^(BOOL success) {
NSLog(@"AppDelegate: new document opened from iCloud");
}];
}];
}
}
- (void)queryDidFinishGathering:(NSNotification *)notification {
// (3) if Query is finished, this will send the result (i.e. either it found our text.dat or it didn't) to the next function
NSMetadataQuery *query = [notification object];
[query disableUpdates];
[query stopQuery];
[self loadData:query];
[[NSNotificationCenter defaultCenter] removeObserver:self name:NSMetadataQueryDidFinishGatheringNotification object:query];
_query = nil; // we're done with it
}
-(void)loadDocument {
// (2) iCloud query: Looks if there exists a file called text.txt in the cloud
NSMetadataQuery *query = [[NSMetadataQuery alloc] init];
_query = query;
//SCOPE
[query setSearchScopes:[NSArray arrayWithObject:NSMetadataQueryUbiquitousDocumentsScope]];
//PREDICATE
NSPredicate *pred = [NSPredicate predicateWithFormat: @"%K == %@", NSMetadataItemFSNameKey, @"text.txt"];
[query setPredicate:pred];
//FINISHED?
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(queryDidFinishGathering:) name:NSMetadataQueryDidFinishGatheringNotification object:query];
[query startQuery];
}
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
NSLog(@"AppDelegate: app did finish launching");
self.window = [[[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]] autorelease];
// Override point for customization after application launch.
if ([[UIDevice currentDevice] userInterfaceIdiom] == UIUserInterfaceIdiomPhone) {
self.viewController = [[[ViewController alloc] initWithNibName:@"ViewController_iPhone" bundle:nil] autorelease];
} else {
self.viewController = [[[ViewController alloc] initWithNibName:@"ViewController_iPad" bundle:nil] autorelease];
}
self.window.rootViewController = self.viewController;
[self.window makeKeyAndVisible];
// (1) iCloud: init
NSURL *ubiq = [[NSFileManager defaultManager] URLForUbiquityContainerIdentifier:nil];
if (ubiq) {
NSLog(@"AppDelegate: iCloud access!");
[self loadDocument];
} else {
NSLog(@"AppDelegate: No iCloud access (either you are using simulator or, if you are on your phone, you should check settings");
}
return YES;
}
@end
用户界面文档
// MyTextDocument.h
// iCloudText
#import <Foundation/Foundation.h>
#import "ViewController.h"
@interface MyTextDocument : UIDocument {
NSString *documentText;
id delegate;
}
@property (nonatomic, retain) NSString *documentText;
@property (nonatomic, assign) id delegate;
@end
// MyTextDocument.m
// iCloudText
#import "MyTextDocument.h"
#import "ViewController.h"
@implementation MyTextDocument
@synthesize documentText = _text;
@synthesize delegate = _delegate;
// ** READING **
- (BOOL)loadFromContents:(id)contents ofType:(NSString *)typeName error:(NSError **)outError
{
NSLog(@"UIDocument: loadFromContents: state = %d, typeName=%@", self.documentState, typeName);
if ([contents length] > 0) {
self.documentText = [[NSString alloc] initWithBytes:[contents bytes] length:[contents length] encoding:NSUTF8StringEncoding];
}
else {
self.documentText = @"";
}
NSLog(@"UIDocument: Loaded the following text from the cloud: %@", self.documentText);
// update textView in delegate...
if ([_delegate respondsToSelector:@selector(noteDocumentContentsUpdated:)]) {
[_delegate noteDocumentContentsUpdated:self];
}
return YES;
}
// ** WRITING **
-(id)contentsForType:(NSString *)typeName error:(NSError **)outError
{
if ([self.documentText length] == 0) {
self.documentText = @"New Note";
}
NSLog(@"UIDocument: Will save the following text in the cloud: %@", self.documentText);
return [NSData dataWithBytes:[self.documentText UTF8String] length:[self.documentText length]];
}
@end
视图控制器
//
// ViewController.h
// iCloudText
#import <UIKit/UIKit.h>
@class MyTextDocument;
@interface ViewController : UIViewController <UITextViewDelegate> {
IBOutlet UITextView *textView;
}
@property (nonatomic, retain) UITextView *textView;
@property (strong, nonatomic) MyTextDocument *document;
-(void)noteDocumentContentsUpdated:(MyTextDocument *)noteDocument;
@end
// ViewController.m
// iCloudText
#import "ViewController.h"
#import "MyTextDocument.h"
@implementation ViewController
@synthesize textView = _textView;
@synthesize document = _document;
-(IBAction)dismissKeyboard:(id)sender {
[_textView resignFirstResponder];
}
-(void)noteDocumentContentsUpdated:(MyTextDocument *)noteDocument
{
NSLog(@"VC: noteDocumentsUpdated");
_textView.text = noteDocument.documentText;
}
-(void)textViewDidChange:(UITextView *)theTextView {
NSLog(@"VC: textViewDidChange");
_document.documentText = theTextView.text;
[_document updateChangeCount:UIDocumentChangeDone];
}