I have an application that has a UITabBarController with two tabs, each having its own navigation controller. Now I want to store the state of the application when the user closes it, so that when the user relauches the application will show the same place as the last time before it was closed.
So, in applicationWillTerminate: I have
[NSKeyedArchiver archiveRootObject:tabBarController toFile:#"lastVisitedTab"];
Then, in applicationDidFinishLaunching: I have
UITabBarController *last= (UITabBarController *)[NSKeyedUnarchiver unarchiveObjectWithFile:#"lastVisitedTab"];
if (last)
tabBarController = [last retain];
I also have an extension to UIImage to make it compliant to NSCoding. However, this doesn't work, as the state is not preserved. The first tab gets selected all the time, and no navigation is preserved either.
Can someone tell me what's wrong, or show me how to do it correctly?
I think it's overkill to persist the actual objects. Instead, just save the selectedIndex property (use [NSNumber numberWithInt: tabBar.selectedIndex]) and then read it back and set the property on launch. Maybe this doesn't properly answer your question, but it might be sufficient for what you are trying to achieve.
I figured out how to do it finally, thanks to Felixyz's idea. Below is what I have to do to store tabs, regardless of their data. If, says, a view is loaded with data downloaded from an URL, store the URL instead of the whole view. You would have to override
- (void)encodeWithCoder:(NSCoder *)encoder
- (id)initWithCoder:(NSCoder *)decoder
in your UIViewController subclass to tell the view controller to save appropriate data before the application stops.
Now in your application delegate save the data before quiting
- (void)applicationWillTerminate:(UIApplication *)application
// data buffer for archiving
NSMutableData *data = [NSMutableData data];
NSKeyedArchiver *archiver = [[NSKeyedArchiver alloc] initForWritingWithMutableData:data];
// the index of selected tab
[archiver encodeInt:tabBarController.selectedIndex forKey:#"TAB_INDEX"];
// array of keys for each navigation controller, here I have 3 navigation controllers
NSArray *keys = [NSArray arrayWithObjects:
#"NAVIGATION_CONTROLLER_1",
#"NAVIGATION_CONTROLLER_2",
#"NAVIGATION_CONTROLLER_3", nil];
for (int i = 0; i < keys.count; i++) {
UINavigationController *controller = [tabBarController.viewControllers objectAtIndex:i];
NSMutableArray *subControllers = [NSMutableArray arrayWithArray:controller.viewControllers];
// the first view controller would already be on the view controller stack and should be removed
[subControllers removeObjectAtIndex:0];
// for each of the navigation controllers save its view controllers, except for the first one (root)
[archiver encodeObject:subControllers forKey:[keys objectAtIndex:i]];
}
[archiver finishEncoding];
// write that out to file
NSString *documentsDirectory = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
[data writeToFile:[documentsDirectory stringByAppendingPathComponent:#"ARCHIVE_PATH"] atomically:YES];
}
And then, when relaunching
- (void)applicationDidFinishLaunching:(UIApplication *)application {
// set up the tabs
tabBarController = [[UITabBarController alloc] init];
tabBarController.viewControllers = [NSArray arrayWithObjects:
[[[UINavigationController alloc] initWithRootViewController:rootViewController1] autorelease],
[[[UINavigationController alloc] initWithRootViewController:rootViewController2] autorelease],
[[[UINavigationController alloc] initWithRootViewController:rootViewController3] autorelease], nil];
// look for saved data, if any
NSString *documentsDirectory = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
NSData *archive = [NSData dataWithContentsOfFile:[documentsDirectory stringByAppendingPathComponent:#"ARCHIVE_PATH"]];
// if no data found, skip this step
if (archive) {
NSKeyedUnarchiver *unarchiver = [[NSKeyedUnarchiver alloc] initForReadingWithData:archive];
// set the tab
tabBarController.selectedIndex = [unarchiver decodeIntForKey:#"TAB_INDEX"];
NSArray *keys = [NSArray arrayWithObjects:
#"NAVIGATION_CONTROLLER_1",
#"NAVIGATION_CONTROLLER_2",
#"NAVIGATION_CONTROLLER_3", nil];
// push view controllers up the stack
for (int i = 0; i < keys.count; i++) {
NSArray *controllers = [unarchiver decodeObjectForKey:[keys objectAtIndex:i]];
for (UIViewController *controller in controllers) {
[((UINavigationController *)[tabBarController.viewControllers objectAtIndex:i]) pushViewController:controller animated:NO];
}
}
}
// Add the tab bar controller's current view as a subview of the window
[window addSubview:tabBarController.view];
}
Related
I'm new to iPhone development and have had great success with with answers from here so I am hoping to receive help directly. I am reading data into a tableview from a plist. The application works fine but I get 2 warnings when I compile. I know why I get the errors but I have been unsuccessful with resolving the issues. Although this app works I really would like to resolve the warnings efficiently. When I tried changing the NSDictionary to NSArray the warning goes away but the table is no longer populated.
Any help would be greatly appreciated.
Staff and Data are defined as NSArray in the Delegate .h file. The warnings show in the delegate .m file below.
My Delegate has the following:
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
// Override point for customization after application launch.
// Add the tab bar controller's current view as a subview of the window
NSString *Path = [[NSBundle mainBundle] bundlePath];
NSString *DataPath = [Path stringByAppendingPathComponent:#"Data.plist"];
NSString *SPath = [[NSBundle mainBundle] bundlePath];
NSString *StaffPath = [SPath stringByAppendingPathComponent:#"Staff.plist"];
NSDictionary *tempDict = [[NSDictionary alloc] initWithContentsOfFile:DataPath];
**self.data = tempDict;**
[tempDict release];
NSDictionary *staffDict = [[NSDictionary alloc]initWithContentsOfFile:StaffPath];
**self.staff = staffDict;**
[staffDict release];
In my staff ViewController I have the following:
if(CurrentLevel == 0) {
//Initialize our table data source
NSArray *staffDict = [[NSArray alloc] init];
self.tableDataSource = staffDict;
[staffDict release];
Midwest_DigestiveAppDelegate *AppDelegate = (Midwest_DigestiveAppDelegate *)[[UIApplication sharedApplication] delegate];
self.tableDataSource = [AppDelegate.staff valueForKey:#"Rows"];
}
else
self.navigationItem.title = CurrentTitle;
An NSArray holds a one dimensional list of items where an NSDictionary maps keys to values.
Array:
[a, b, c]
Dictionary:
{#"a" = #"first item", #"b" = #"second item"}
Could you declare data as NSDictionary *data; and populate it as data = [[NSDictionary alloc] initWithContentsOfFile:DataPath];
You then access values in the dictionary with [data valueForKey:#"key"]
Everything in your code suggests that the staff and data properties are NSDictionary instances. You initialize them to dictionary objects and you reference them as dictionary objects. Why then are you declaring them as NSArray objects?
You should change how they are declared so they are NSDictionary in your header file rather than NSArray. That seems to me the most logical way to remove your warnings.
This should still work assuming the contents of your "staff" NSDictionary has a key named "Rows" whose value is an NSArray. The code you have to initialize self.tableDataSource with an empty NSArray seems redundant, as you immediately overwrite the value with the
self.tableDataSource = [AppDelegate.staff valueForKey:#"Rows"];
line in your code
I'm struggling to find the correct way to release an array after my method has been called. I wonder if there is a better way to achieve what I'm trying to acheive with my method:
- (NSArray *) setupDetailArray : (NSString *) selectedCategory {
// Load .plist file
NSString *path = [[NSBundle mainBundle] pathForResource:#"data" ofType:#"plist"];
// Load .plist into a new dictionary
NSDictionary *dict = [[NSDictionary alloc] initWithContentsOfFile:path];
// Drill down to next level
NSArray *faceSelection = [[NSArray alloc] initWithArray:[dict objectForKey:detailTitle]];
[dict release], dict = nil;
// Set up link to App Delegate
UltimateRageAppDelegate *dataCenter = (UltimateRageAppDelegate *) [[UIApplication sharedApplication] delegate];
dataCenter.faces = [[NSMutableArray alloc] init];
// Set app delegate faces to array
dataCenter.faces = faceSelection;
[dataCenter.faces release];
return faceSelection;
// [faceSelection release], faceSelection = nil; ??????
}
And I call my method in viewDidLoad
// If faceArray is empty, create it
if (faceArray == nil)
faceArray = [self setupDetailArray:detailTitle];
...
My application is leaking memory here, and I'm really looking for a way to release everything once I'm done.
Your method should return an autoreleased array which is then retained by the method that calls it if it wants/needs to keep it.
- (NSArray *) setupDetailArray : (NSString *) selectedCategory {
...
// Create the array, but don't own it
NSArray *faceSelection = [[[NSArray alloc] initWithArray:[dict objectForKey:detailTitle]] autorelease];
...
return facesSelected;
}
Now the code that calls this method should retain the object if it needs it. So, in your viewDidLoad
if (faceArray == nil)
faceArray = [[self setupDetailArray:detailTitle] retain];
...
If faceArray is an instance variable in your class, then you can just release it in your dealloc method.
You are also leaking memory here
// Set up link to App Delegate
UltimateRageAppDelegate *dataCenter = (UltimateRageAppDelegate *) [[UIApplication sharedApplication] delegate];
dataCenter.faces = [[NSMutableArray alloc] init];
// Set app delegate faces to array
dataCenter.faces = faceSelection;
[dataCenter.faces release];
This should be
// Set up link to App Delegate
UltimateRageAppDelegate *dataCenter = (UltimateRageAppDelegate *) [[UIApplication sharedApplication] delegate];
dataCenter.faces = faceSelection;
I'd suggest you read (and re-read and re-read) the docs on memory management and read up on properties, setters and the dot notation.
Apple Objective-C Memory Management
dataCenter.faces = [[NSMutableArray alloc] init];
You allocate a non-autoreleased array and assign it to the property faces (I bet it has the retain modifier).
dataCenter.faces = faceSelection;
Now you assign as new array to the faces property, but you haven't properly release the previous NSMutableArray.
[dataCenter.faces release];
You now indirectly release your faceSelection array.
You leak at least one NSMutableArray every time you run that method. You should do it like this instead:
// Drill down to next level
NSArray *faceSelection = [[dict objectForKey:detailTitle] copy];
[dict release], dict = nil;
// Set up link to App Delegate
UltimateRageAppDelegate *dataCenter = (UltimateRageAppDelegate *) [[UIApplication sharedApplication] delegate];
// Set app delegate faces to array
dataCenter.faces = faceSelection;
return [faceSelection autorelease];
Your method should return an autoreleased object. The only methods that should return retained objects are methods whose name:
starts with alloc
starts with new
contains copy
All other methods should return autoreleased objects.
Other way for doing this.
//Declare method as follows.
- (void) setupDetailArray : (NSString *) selectedCategory arrFaceArray:(NSArray *)faceArray
{
}
And I call my method in viewDidLoad
if (!faceArray)
{
faceArray = [[NSArray alloc] init]; //Alloc in ViewDidLoad and release in ViewDidUnload or dealloc.
faceArray = [self setupDetailArray:detailTitle arrFaceArray:faceArray];
}
Also consider the #DarkDust answer for maintaining autoreleased objects. Both are the possible ways.
I am trying to addObject to a NSMutableArray once the user taps the Add to Favorites button I can get the data into a NSDictionary, but when I pass the NSDictionary to the Array the NSLog comes back with nil. Am I missing something?
-(IBAction) addtofavorites: (id)sender
{
NSArray *key = [NSArray arrayWithObjects:#"Title", #"Description", nil];
NSArray *objects = [NSArray arrayWithObjects:CurrentTitle, description.text, nil];
NSDictionary *fadd = [[NSDictionary alloc] initWithObjects:objects forKeys:key];
FavoritesViewController *fvc = [[FavoritesViewController alloc] init];
[fvc.favorites addObject:fadd];
[FavoritesViewController release];
}
What I would do is in your header file create an instance variable for your FavoritesViewController that you retain. Then use lazy init when the addtofavorites is pressed. Something like below
if (!detailViewController)
{
self.fvc = [[FavoritesViewController alloc] init];
}
[self.fvc.favorites addObject:fad];
Then just release the FavoritesViewController object in dealloc
- (void)dealloc {
[fvc release];
[super dealloc];
}
FavoritesViewController *fvc = [[FavoritesViewController alloc] init];
[fvc.favorites addObject:fadd];
[FavoritesViewController release];
doesn't look right. You should already have a FavoritesViewController initialized (in which can just access it and call -addObject:)...
EDIT
First, how does the current view controller (the one that has -addtofavorites: defined on it) relate to FavoritesViewController? How would the user navigate between these two view controllers?
Second, would the list of favorites persist across different runs of the app? If so, how do you plan to save/restore favorites?
Third, rather than add favorites to a view controller, you would probably do better to add them to an underlying 'model' that would be used to populate the FavoritesViewController.
Separating the 'model' from the 'view' can be very powerful, while also simplifying your code.
There are multiple memory leaks in this section of my code. Specifically with these arrays: PlaylistItem, PlaylistItemID and PlaylistItemLength. The problem is that I can't successfully release the arrays. When I attempt to use insert [xxxx release]; anywhere in this code, the app locks up. It's driving me absolutely nurtz!
-(void)configureCueSet {
MPMediaQuery *myPlaylistsQuery = [MPMediaQuery playlistsQuery];
NSArray *playlists = [myPlaylistsQuery collections];
//Get # of items in a playlist and names -------------------------------------
NSArray *songs;
for (MPMediaPlaylist *playlist in playlists) {
NSString *playListItem = [playlist valueForProperty: MPMediaPlaylistPropertyName];
if ([playListItem isEqualToString: savedLastSelectedPlaylist]){
songs = [playlist items];
}
}
PlaylistItem = [[NSMutableArray alloc] init];
PlaylistItemID = [[NSMutableArray alloc] init];
PlaylistItemLength = [[NSMutableArray alloc] init];
for (MPMediaItem *song in songs) {
[PlaylistItem addObject:[song valueForProperty: MPMediaItemPropertyTitle]];
[PlaylistItemID addObject:[song valueForProperty: MPMediaItemPropertyPersistentID]];
[PlaylistItemLength addObject:[song valueForProperty: MPMediaItemPropertyPlaybackDuration]];
}
}
Does that method get called multiple times? If so, your leak likely occurs on that assignment. You'd want:
[PlayListItem release];
PlaylistItem = [[NSMutableArray alloc] init];
[PlayListItemID release];
PlaylistItemID = [[NSMutableArray alloc] init];
[PlaylistItemLength release];
PlaylistItemLength = [[NSMutableArray alloc] init];
If you don't release what was there before, then you'll get a leak.
Attempting to insert [xxx release] would release the contents, not the arrays. The application crashes because with that you are deallocating the object which you are about to add to the array. According to the documentation (here), the values in an NSArray are automatically retained, and will be released as soon as the array is dealloc'ed. So, if you want to release any of those arrays, simply type [PlaylistItem release].
I've got a tableView in a view which is a subview to my MainViewController. When the subview is loaded, I have this in my viewDidLoad method to initialize my tableData:
NSMutableArray *array = [[NSMutableArray alloc] init];
self.listData = array;
[array release];
[super viewDidLoad];
Then I use other methods to add to this data within this view.
When I switch back to my other view, however, then bring up this view again, it initializes the data all over again, erasing my changes. How can I fix this problem?
EDIT:
I tried to initialize this array in MainViewController by doing this:
NSMutableArray *array = [[NSMutableArray alloc] init];
HistoryViewController.listData = array;
[array release];
But it says Accessing unknown 'setListData:' class method.
you should not be initializing your array in view did load
// this is clearing out all of your data
NSMutableArray *array = [[NSMutableArray alloc] init];
self.listData = array;
There is not much code, but I would suggest initializing the listData property when you initialize the ViewController.
I might suggest you review this tutorial here on UITableView, and your code above should be edited
HistoryViewController.listData = array;
should be
self.listData = array;