Custom view controller transition and animation

iOS7 introduced a way by which we can customise the transition from one view controller to other. For example say if we  navigate from one view controller to another  , we push a view controller on another and to return back to initial view controller we pop the view controller.
With iOS7 now we can change the animation according to out requirement. We can reverse the direction of navigation controller. Even we can change the direction of the presenting view controller .
For creating custom transitioning we have to perform following steps:

1) Create a class that implements the UIViewControllerAnimatedTransitioning protocol . In this class we code to customise the animation . In this class we implements the two delegate method of the above protocol , which is as:

-(NSTimeInterval)transitionDuration:(id<UIViewControllerContextTransitioning>)transitionContext{

    return 1.5;

}

-(void)animateTransition:(id<UIViewControllerContextTransitioning>)transitionContext{}

2) In view controller class (a view controller from which we navigate or transition to another  view controller), implements the following:

       If we are presenting a view controller modally, then view controller have to implement UIViewControllerTransitioningDelegate . UIviewController has a property named transitionDelegate set it to self in order to return the custom animation for transitioning .
In delegate method (animationControllerForPresentedController) return the instance of the class which implements the  UIViewControllerAnimatedTransitioning .

      If we are navigating from one view controller to another , the view controller have to implement UINavigationControllerDelegate . The set the view controller as delegate of the navigation controller . And implement the required methods .
For customising the push and pop operation , we can create the two classes one for push animation and another for pop operation which implements the UIViewControllerAnimatedTransitioning . 
And then  from the delegate method of the navigation controller we can check the type of operation (push or pop)and return the  designated custom animator instance .

- (nullable id <UIViewControllerAnimatedTransitioning>)navigationController:(UINavigationController *)navigationController animationControllerForOperation:(UINavigationControllerOperation)operation fromViewController:(UIViewController *)fromVC toViewController:(UIViewController *)toVC{

}

With this way we can create the custom animation as we want. The core part of this process is to code the custom animation . And return the instance of the  custom animation objects.

References: http://www.appcoda.com/custom-view-controller-transitions-tutorial/

Show download progress of the content

In iOS when we download any content , there may be a need to show the progress of the download. It's easy in iOS. We can download the data with NSURLConnection. 

First of all create a UIProgressBar in your view and initially make it hidden. Lets say we have a progress bar outlet named  progressBar .


1) Create NSURLConnection object

NSURL *url = [NSURL URLWithString:@"Your_url"];

    NSURLRequest *request = [NSURLRequest requestWithURL:url         cachePolicy:NSURLRequestReloadIgnoringLocalCacheData timeoutInterval:80];

   NSMutableData *dataReceived = [[NSMutableData alloc] initWithLength:0];

    NSURLConnection * connection = [[NSURLConnection alloc] initWithRequest:theRequest delegate:self     startImmediately:YES];

2) Now implement the delegate methods of the NSURLConnection

 In this method we receive the response of the download, from which we get the expected content length.Also we make the progress bar unhidden here.

- (void) connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {

     self.progressBar.hidden = NO;

    [dataReceived setLength:0];

    long long  expectedDataBytes = [response expectedContentLength];

}

In didReceiveData:(NSData*)data method we get the downloaded data chunks, here we append the data to dataReceived object . And also set the progress bar by download progress .

- (void) connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {

    [dataReceived appendData:data];

    float downloadProgress = (float)[dataReceived length] / (float) expectedDataBytes;

     [self.progressBar setProgress: downloadProgress];

    

}

When downloading is complete the connectionDidFinishLoading:(NSURLConnection*)connection method is called. Here we can save the downloaded content to the document directory.

- (void) connectionDidFinishLoading:(NSURLConnection *)connection {

   

}

    

Here I make the expectedDataBytes and dataReceived object local .You have to declare them to interface section of the file to use them in all methods.

Reference:

http://stackoverflow.com/questions/16453655/objective-c-downloading-file-with-progress-bar

Custom AVPlayer

In iOS application development some time we may have situation where we want to show our own controls on AVPlayer. Suppose user want to show the playback slider on the bottom of the screen and two buttons on the left and right side of the screen  to control the speed of the video .

To implement this  we can create a view with required buttons and slider and assign action to designated view controller. The steps are as follows:

1) Create a view controller and then design the xib as per the need and create necessary outlets and action of the objects .

2) Then in implementation file create an instance of AVPlayerItem .

NSURL *url  =[NSURL URLWithString:@"http://clips.vorwaerts-gmbh.de/big_buck_bunny.mp4"];

    //create player item

AVPlayerItem *playerItem = [AVPlayerItem playerItemWithURL:url];

3)  Initialize AVPLayer with the AVPlayerItem instance

   AVPlayer *player = [AVPlayer playerWithPlayerItem:playerItem];

4)  Create an AVPLayerLayer instance

   AVPlayerLayer *playerLayer = [AVPlayerLayer playerLayerWithPlayer:player];

5) Now insert the playerLayer to the view's layer hierarchy

    [self.view.layer insertSublayer:playerLayer atIndex:0];

That's all our design is done. 

Now our job is to run the slider, speed the video when user tap on button and  play and pause the video .To implement these all feature we can register observer .

6) To check the status of the playing item we can register for key path observing like this :

[playerItem addObserver:self forKeyPath:@"status" options:NSKeyValueObservingOptionOld|NSKeyValueObservingOptionNew context:nil];

Then implement the method

-(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary<NSString *,id> *)change context:(void *)context{

}

This method is core method of KVO(Key-value-observing) and is called every time when any changes occur in the property of the registered object .In this method we can check for different key path and take action accordingly like this :

if ([keyPath isEqualToString:@"status"]) {

 }

7)To track the buffering of the video register for key path playbackLikelyToKeepUp

[playerItem addObserver:self forKeyPath:@"playbackLikelyToKeepUp" options:NSKeyValueObservingOptionNew context:nil];

8) We can register an observer to listen for when the video is ended :

[[NSNotificationCenter defaultCenter]addObserver:self selector:@selector(playerDidEndVideo) name:AVPlayerItemDidPlayToEndTimeNotification object:nil];

Slide down a UIView on a button action

In iOS app, we may have a requirement like, when a user tap on a button , a UIView slide down with animation . To implement this we can create a button and UIView on the top of button and make it hidden . Then in action method of the button change the frame of the UIView with animation  according to our requirement . To make it hide again with animation like slide top, reverse the operation .

Here is an example in which we will make a UIView slide down when a user tap on the button.

1) Create a UIButton

2) Then create a UIView on the top of UIButton  and make it hidden . Lets say we named it myView

3) Then in action method of UIButton , check if button is hidden or not and act accordingly:

if([myView isHidden]){

 First unhide the button

myView.hidden = NO;
 
Get the frame of the btn

CGRect frame  = myView.frame

Now change the y origin of the  frame

frame.origin.y += 30;

Now set animation to change the frame of the myView

[UIView animateWithDuration:0.7 delay:0.0
options:UIViewAnimationOptionCurveLinear animations:^{

      myView.frame  = frame

} completion:nil];


That's all . Now if we want to slide top the myView again ,when user tap on the button then change the frame of the myView to its original size .

Integrate google map in an iOS app

In iOS development we have situation where we need to add  a map in our app. Google provides the iOS SDK to integrate map in an iOS app.

We can add SDK  either manually or using COCOAPODS. Here we are adding through pod .

Before adding google map SDK make sure we have COCOAPOD install in out system. If we have po d in our system  then follow these steps  to make a pod file :

1) Go to project directory and run the command
     
                pod init

This will make a pod file in your project directory.

2) Now open the Podfile

            nano Podfile

Add the following lines to add google map in our project:

    source 'https://github.com/CocoaPods/Specs.git'

target 'Indi Beats' do

pod 'GoogleMaps'

  pod 'GooglePlaces'

end

Now save and exit the pod file and run the pod install command to add the google map. This will make a file with an extension of  .xcworkspace . Now open this file to open the project in xocode .

Now go to developer site of google and follow these steps to enable the Google maps SDK for iOS on the  Google API console .

1) Go to Google API Console .

2) Creare or select a project .

3) Click Continue to enable the Google Maps SDK for iOS.

4) On the Credentials page, get an iOS key and enter your app's bundle identifier when prompted .

5) Click Create .

This will create  an API key for Google Maps .

Add API key in iOS application:

Add API key  in your AppDelegate.m file

1) Add the import statement:

      

      @import GoogleMaps;

2) In application:didFinishWithLaunchingOptions: method, add the following line:

      [GMSServices provideAPIKey:@"your api key"];

Add a map :

In your view controller add the following  import statement:

#import <GoogleMaps/GoogleMaps.h> 

-(void)addMap{

//1  Create camera position

      GMSCameraPosition *cameraPos =  [GMSCameraPosition cameraWithLatitude:-33.86 longitude:151.20 zoom:10];

//2 Create map view

     GMSMapView *mapView = [GMSMapView  mapWithFrame:CGRectZero camera:cameraPos];

     self.view = mapView ;

//3 We can also create a marker

     GMSMarker *marker =  [GMSMarker alloc]init];

    

     //set position of the marker

      marker.position = CLLocationCoordinate2DMake(-33.86,151.20);

      

      marker.map =  mapView ;

}

That's it. This is how we add a map in an iOS app,

Reference: https://developers.google.com/maps/documentation/ios-sdk/start

Category in Objective C

A category provides an easy way for you to modularize the definition of a class into groups or categories of related methods. It also gives you an easy way to extend an existing class definition without even having access to the original source code for the class and without having to create a subclass. 

For example: we have a class Fraction, which look like as:

#import <Foundation/Foundation.h> // Define the Fraction class

@interface Fraction : NSObject

 @property int numerator, denominator;

-(void) setTo: (int) n over: (int) d; 

-(Fraction *) add: (Fraction *) f; -(void) reduce;
-(double) convertToNum;

-(void) print; 

@end

If we want to crate a mathOps category that will include the method to perform math operation:

Steps are as follows:

We can create category in separate category file or in to the original file as  class in.

1) import the class for which you want to create a category.

#import Fraction.h

Even though this is an interface section definition, it is an extension to an existing one.Therefore, you must import the original interface section so that the compiler knows about the Fraction class (unless you incorporate the new category directly into the original Fraction.h header file, which is an option). 

2) add interface 

@interface Fraction(category_name)

// add methods here

-(Fraction *) add: (Fraction *) f;

-(Fraction *) mul: (Fraction *) f; 

-(Fraction *) sub: (Fraction *) f; 

-(Fraction *) div: (Fraction *) f; 

@end 

The category name is enclosed in parentheses after the class name. Notice that you don’t list the Fraction’s parent class here; the compiler already knows it from Fraction.h.Also, you don’t tell it about the instance variables .

3) You can put the definitions for all your methods into a single implementation section. That is, you could define all the methods from the interface section in Fraction.h plus all the methods from the MathOps category in one implementations section.

Alternatively, you could define your category’s methods in a separate implementation section. In such a case, the implementation section for these methods must also identify the category to which the methods belong. As with the interface section, you do this by enclosing the category name inside parentheses after the class name, like this: 

@implementation Fraction(category_name)

// code for category methods

@end

Remember that extending a class by adding new methods with a category affects not just that class, but all its subclasses as well. 

Class Extensions:

There is a special case of creating a category without a name, that is no name is specified between the ( and ).This special syntax defines what is known as a class extension.When you define an unnamed category like this, you can extend the class by defining additional instance variables.This is not allowed for named categories. Methods declared in an unnamed category are implemented in the main implementation section for the class and not in a separate implementation section.

Let’s assume we have a class called GraphicObject. Further assume we type the following lines into

our implementation file GraphicObject.m:

#import "GraphicObject.h"

// Class extension

@interface GraphicObject ()

 @property int uniqueID;

-(void) doStuffWithUniqueID: (int) theID;

 @end

@implementation GraphicObject 

@synthesize uniqueID;

(void) doStuffWithUniqueID: (int) myID

{
self.uniqueID = myID;

... }

...
// Other GraphicObject methods ...

@end

Unnamed categories are useful because their methods are private. So if you need to write a class that has data and methods that can only be used within the class itself, an unnamed category might just fit the bill. 

Add multiple buttons to a UITableView cell on swipe

When we want to add some action to a table view cell when swipe , Apple provides the methods to deal with it. But by default Apple gives only one button when we swipe to left, a delete button . But what if we want more buttons like a mail app in iOS 8.

In iOS8 Apple provides this functionality in form of edit actions and UITableViewRowAction.

To use UITableViewRowAction we have to implement a delegate method of UITableView:

-(NSArray<UITableViewRowAction *> *)tableView:(UITableView *)tableView editActionsForRowAtIndexPath:(NSIndexPath *)indexPath{

    //return an array of UITableViewRowAction instances

}

In this method we create the UITableViewRowAction instance like this:

UITableViewRowAction *delete = [UITableViewRowAction rowActionWithStyle:UITableViewRowActionStyleDefault title:@"Delete" handler:^(UITableViewRowAction * _Nonnull action, NSIndexPath * _Nonnull indexPath) {

       

        //call method to perform action when user tap on delete button   

    }];

The above code will create a delete instance and provide handler block which will be executed when user tap on the targeted  UITableViewRowAction instance.

Like this we can create multiple instances of the UITableViewRowAction  and finally return an array of UITableViewRowAction instances.

How that's simple it is to add multiple button to a table view cell on swipe.But to enable user to perform action on these multiple buttons we have to enable users to allow editing on the table view cell. To do this, implement these two table view delegate methods:

To allow editing on cell, implement:

-(BOOL)tableView:(UITableView *)tableView canEditRowAtIndexPath:(NSIndexPath *)indexPath{

    return YES;

}

It is necessary to override this second method, even though we can leave it blank. If method is not present the action won't show up on swipe.

-(void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath{

    

    //to do when commiting editing

}