Step by Step: objective C

Showing posts with label objective C. Show all posts

Objective C: UITableView: Detect which section header on top

static NSInteger currentTopVisibleSection = -1;

- (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section {
    NSIndexPath *topCellPath = [[tableView indexPathsForVisibleRows] objectAtIndex:0];
    if (currentTopVisibleSection != topCellPath.section) {
        currentTopVisibleSection = topCellPath.section;
        NSLog(@"current section on top is %d", currentTopVisibleSection);
    }

    NSString *header = [NSString stringWithFormat:@"Section %d", section];
    return header;
}

Objective C: UITextField controlling background image/color

If you set

UITextField *tf = [[UITextField alloc] init];
tf.borderStyle = UITextBorderStyleRoundedRect;

you can't control background of text field. To controlling background you need

#import "QuartzCore/QuartzCore.h"
...

UITextField *tf = [[UITextField alloc] init];
tf.borderStyle = UITextBorderStyleDefault;
tf.background = [UIImage imageNamed:@"bg_000000_20.png"];
tf.layer.cornerRadius = 5.0;
tf.layer.masksToBounds = YES;

// for vertical align
tf.contentVerticalAlignment = UIControlContentVerticalAlignmentCenter;

// for border
tf.layer.borderWidth = 1.0;
tf.layer.borderColor = [[UIColor darkGrayColor] CGColor];

// for left padding
tf.leftView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 5, 20)];
tf.leftViewMode = UITextFieldViewModeAlways;

Objective C: Detect start of bouncing effect for UIScrollView

For detect bouncing of UIScrollView (or UITableView ...) using UIScrollViewDelegate:

static BOOL _draggingView = NO;

- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView {
 _draggingView = YES;
}

- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate {
 _draggingView = NO;
}

- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
 NSInteger pullingDetectFrom = 50;
 if (self.contentOffset.y < -pullingDetectFrom) {
  _draggingView = NO;
  NSLog(@"Pull Down");
 } else if (self.contentSize.height <= self.frame.size.height && self.contentOffset.y > pullingDetectFrom) {
  _draggingView = NO;
  NSLog(@"Pull Up");
 } else if (self.contentSize.height > self.frame.size.height && 
       self.contentSize.height-self.frame.size.height-self.contentOffset.y < -pullingDetectFrom) {
  _draggingView = NO;
  NSLog(@"Pull Up");
 }
}

Objective C: Sort array of objects

If we have array of some objects:

@interface SimpleObject : NSObject {
 NSInteger key;
 NSString *name;
        . . .
}

and we need to sort this array by "name" property of SimpleObject. Use NSSortDescriptor:

// declare array with SimpleObject instances
self.simpleObjectsArray = . . .

NSSortDescriptor *sortDescriptor =
        [[[NSSortDescriptor alloc] initWithKey:@"name" ascending:YES] autorelease];
NSArray *sortDescriptors = 
        [NSArray arrayWithObject:sortDescriptor];
// array contained all instances sorted by "name" field
NSArray *sortedArray = 
        [self.simpleObjectsArray sortedArrayUsingDescriptors:sortDescriptors];

Objective C: Bring back user to your application during/after he End the Call

Sometime you need come back to application after phone call initiated by your own application.

Exist two options (each from them not 100% that do you want), but if no choice..

After starting phone call you getting local notification alert with two option

Cancel (stay on call screen)
Return (back to application during your call)

NSURL *phoneSchemaURL = [NSURL URLWithString:@"tel://123456789"];
 
[[UIApplication sharedApplication] openURL:phoneSchemaURL];

UILocalNotification *localNotification = [[UILocalNotification alloc] init];
if (localNotification != nil) {
 NSDate *notificationDate = [[NSDate alloc] initWithTimeIntervalSinceNow: 3];
  
 localNotification.fireDate = notificationDate;
 [notificationDate release];
  
 localNotification.alertBody = @"Stay in app";
 localNotification.alertAction = @"Return";
  
 localNotification.soundName = UILocalNotificationDefaultSoundName;
  
 [[UIApplication sharedApplication] scheduleLocalNotification:localNotification];
}
[localNotification release];

After ending phone call your application retrieve focus.

NSURL *phoneSchemaURL = [NSURL URLWithString:@"tel://123456789"];
 
 NSString *osVersion = [[UIDevice currentDevice] systemVersion];
 
if([osVersion compare: @"3.1" options: NSNumericSearch] >= NSOrderedSame ) {
 UIWebView *webview = [[UIWebView alloc] initWithFrame:[UIScreen mainScreen].applicationFrame];
 //or if you just want to call and back to application
 //UIWebView *webview = [[UIWebView alloc] init];

 [webview loadRequest:[NSURLRequest requestWithURL:phoneSchemaURL]];
  
 //if you just want to call and back to application remark code below, but don't forget release webview

 [self.view addSubview:webview];
 [webview release];
} else {
 // On 3.0 and below, dial as usual
 [[UIApplication sharedApplication] openURL: phoneSchemaURL];          
}

Objective C: Basic HTTP Authorization

First version of "Authorization":

NSString *loginString = [NSString stringWithFormat:@"%@:%@", [self userName], [self password]];
NSString *encodedLoginData = [Base64 encode:[loginString dataUsingEncoding:NSUTF8StringEncoding]];  
NSString *base64LoginData = [NSString stringWithFormat:@"Basic %@",encodedLoginData];

NSURL *url=[NSURL URLWithString:@"http://my_url.com"];
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url cachePolicy:NSURLRequestReloadIgnoringLocalAndRemoteCacheData
                timeoutInterval:10.0];

[request setHTTPMethod:@"POST"];

[request setValue:base64LoginData forHTTPHeaderField:@"Authorization"];

NSURLConnection *urlConnection = [[NSURLConnection alloc] initWithRequest:request delegate:self];

Second version of "Authorization":

NSURL *URL = [NSURL URLWithString:url];
NSURLRequest *request = [NSURLRequest requestWithURL:URL
                                         cachePolicy:NSURLRequestUseProtocolCachePolicy
                                     timeoutInterval:10.0];

NSURLConnection *connection = [[NSURLConnection alloc] initWithRequest:request delegate:self];

NSURLConnection Delegates

- (void)connection:(NSURLConnection *)connection didReceiveAuthenticationChallenge:(NSURLAuthenticationChallenge *)challenge {
    if ([challenge previousFailureCount] == 0) {
        NSLog(@"received authentication challenge");
        NSURLCredential *newCredential = [NSURLCredential credentialWithUser:@"USER"
                                                                    password:@"PASSWORD"
                                                                 persistence:NSURLCredentialPersistenceForSession];
        NSLog(@"credential created");
        [[challenge sender] useCredential:newCredential forAuthenticationChallenge:challenge];
        NSLog(@"responded to authentication challenge");    
    }
    else {
        NSLog(@"previous authentication failure");
    }
}

Objective C: Change title of back button in navigation bar

You need change title of the back button from view controller which call to next view controller:

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
    if (self.detailsViewController == nil) {
        self.detailsViewController = [[DetailsViewController alloc] initWithNibName:@"DetailsViewController" bundle:nil];
 }
 
 [self.navigationController pushViewController:detailsViewController animated:YES];
 
 [tableView deselectRowAtIndexPath:indexPath animated:YES];
}

- (void)viewDidLoad {
 self.title = NSLocalizedString(@"root_tab_title_0", @"My Title");

 //Set title for back button to this controller
 self.navigationItem.backBarButtonItem =
  [[[UIBarButtonItem alloc] initWithTitle:@"My back button"
      style:UIBarButtonItemStyleBordered
      target:nil
      action:nil] autorelease];
}

Objective C: Change title font in navigation bar

UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(0, 0, 320, 30)];
label.textAlignment = UITextAlignmentCenter;
label.adjustsFontSizeToFitWidth = YES;
label.minimumFontSize = 10.0;
[label setFont:[UIFont boldSystemFontOfSize:16.0]];
[label setBackgroundColor:[UIColor clearColor]];
[label setTextColor:[UIColor whiteColor]];
[label setText:@"My Favorite Title"];

[self.navigationItem setTitleView:label];
[label release];

Xcode: include ObjectiveC categories int static library

If you need to include ObjectiveC categories or other framework using ObjectiveC categories ( for example JSON framework ) into your own static library you probably get

-[__NSCFDictionary JSONRepresentation]: unrecognized selector sent to instance

In your project that using your static library you need to set in Project Settings for "Other Linker Flags" property two additional flags:

-ObjC
-all_load

Objective C: Merge two images

+ (UIImage*)mergeImage:(UIImage*)first withImage:(UIImage*)second
{
 // get size of the first image
 CGImageRef firstImageRef = first.CGImage;
 CGFloat firstWidth = CGImageGetWidth(firstImageRef);
 CGFloat firstHeight = CGImageGetHeight(firstImageRef);
 
 // get size of the second image
 CGImageRef secondImageRef = second.CGImage;
 CGFloat secondWidth = CGImageGetWidth(secondImageRef);
 CGFloat secondHeight = CGImageGetHeight(secondImageRef);
 
 // build merged size
 CGSize mergedSize = CGSizeMake(MAX(firstWidth, secondWidth), MAX(firstHeight, secondHeight));
 
 // capture image context ref
 UIGraphicsBeginImageContext(mergedSize);
 
 //Draw images onto the context
 [first drawInRect:CGRectMake(0, 0, firstWidth, firstHeight)];
 [second drawInRect:CGRectMake(0, 0, secondWidth, secondHeight)]; 
 
 // assign context to new UIImage
 UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
 
 // end context
 UIGraphicsEndImageContext();

 return newImage;
}

If you want to resize new image to new desired size use function from previous post.

Objective C: Resize image

+ (UIImage*)resizeImageWithImage:(UIImage*)image toSize:(CGSize)newSize
{
    // Create a graphics image context
    UIGraphicsBeginImageContext(newSize);
 
    // draw in new context, with the new size
    [image drawInRect:CGRectMake(0, 0, newSize.width, newSize.height)];
 
    // Get the new image from the context
    UIImage* newImage = UIGraphicsGetImageFromCurrentImageContext();
 
    // End the context
    UIGraphicsEndImageContext();
 
    return newImage;
}

Zip/Unzip files on iPhone/iPad/iOS

Download ZipArchive from http://code.google.com/p/ziparchive/downloads/list.
Drag into project.
Add to project existing framework libz.1.2.3.dylib (last version).
Import to project:
```
#import "ZipArchive.h"
```

Uncompress zip file example:

NSString *documentsDirectory = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];

NSString *zipFilePath = [documentsDirectory stringByAppendingPathComponent:@"myZipFileName.zip"];

NSString *output = [documentsDirectory stringByAppendingPathComponent:@"unZipDirName"];

ZipArchive* za = [[ZipArchive alloc] init];

if( [za UnzipOpenFile:zipFilePath] ) {
    if( [za UnzipFileTo:output overWrite:YES] != NO ) {
        //unzip data success
        //do something
    }

    [za UnzipCloseFile];
}

[za release];

Compress directory or file example:

BOOL isDir=NO;

NSString *documentsDirectory = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];

NSArray *subpaths;

NSString *toCompress = [NSString stringWithString:@"dirToZip_OR_fileNameToZip"];
NSString *pathToCompress = [documentsDirectory stringByAppendingPathComponent:toCompress];

NSFileManager *fileManager = [NSFileManager defaultManager]; 
if ([fileManager fileExistsAtPath:pathToCompress isDirectory:&isDir] && isDir){
    subpaths = [fileManager subpathsAtPath:pathToCompress];
} else if ([fileManager fileExistsAtPath:pathToCompress]) {
    subpaths = [NSArray arrayWithObject:pathToCompress];
}

NSString *zipFilePath = [documentsDirectory stringByAppendingPathComponent:@"myZipFileName.zip"];
  
ZipArchive *za = [[ZipArchive alloc] init];
[za CreateZipFile2:zipFilePath];
if (isDir) {
    for(NSString *path in subpaths){  
        NSString *fullPath = [pathToCompress stringByAppendingPathComponent:path];
        if([fileManager fileExistsAtPath:fullPath isDirectory:&isDir] && !isDir){
            [za addFileToZip:fullPath newname:path];  
        }
    }
} else {
    [za addFileToZip:pathToCompress newname:toCompress];
}

BOOL successCompressing = [archiver CloseZipFile2];