Creating
the Project
Using Xcode, create a new View-based
Application project and name it as Bluetooth.
All the various APIs for accessing
the Bluetooth is located in the GameKit framework. Hence, you need to add this
framework to your project. Add a new Framework to the project by right-clicking
on the Frameworks group in Xcode and selecting Add, Existing Frameworks. Select
GameKit.framework
In the BluetoothViewController.h file, declare the following object, outlets, and actions:
#import
#import
@interface
BluetoothViewController : UIViewController {
GKSession
*currentSession;
IBOutlet
UITextField *txtMessage;
IBOutlet
UIButton *connect;
IBOutlet
UIButton *disconnect;
}
@property
(nonatomic, retain) GKSession *currentSession;
@property
(nonatomic, retain) UITextField *txtMessage;
@property
(nonatomic, retain) UIButton *connect;
@property
(nonatomic, retain) UIButton *disconnect;
-(IBAction)
btnSend:(id) sender;
-(IBAction)
btnConnect:(id) sender;
-(IBAction)
btnDisconnect:(id) sender;
@end
The GKSession object is used to
represent a session between two connected Bluetooth devices. You will make use
of it to send and receive data between the two devices.
In the BluetoothViewController.m file, add in the following statements in bold:
#import
"BluetoothViewController.h"
@implementation
BluetoothViewController
@synthesize
currentSession;
@synthesize
txtMessage;
@synthesize
connect;
@synthesize
disconnect;
Double-click on BluetoothViewController.xib to edit it in Interface Builder. Add the following views to
the View window
- Text Field
- Round Rect Button
Perform the following actions:
- Control-click on the File’s Owner item and drag and drop it over the Text Field view. Select txtMessage.
- Control-click on the File’s Owner item and drag and drop it over the Connect button. Select connect.
- Control-click on the File’s Owner item and drag and drop it over the Disconnect button. Select disconnect.
- Control-click on the Send button and drag and drop it over the File’s Owner item. Select btnSend:.
- Control-click on the Connect button and drag and drop it over the File’s Owner item. Select btnConnect:.
- Control-click on the Disconnect button and drag and drop it over the File’s Owner item. Select btnDisconnect:.
Right-click on the File’s Owner item
to verify that all the connections are made correctly.
Back in Xcode, in the BluetoothViewController.m file, add in the following statements in bold:
-
(void)viewDidLoad {
[connect
setHidden:NO];
[disconnect
setHidden:YES];
[super
viewDidLoad];
}
-
(void)dealloc {
[txtMessage
release];
[currentSession
release];
[super
dealloc];
}
Searching
for Peer Devices
Now that all the plumbings for the
project have been done, you can now focus on the APIs for accessing other
Bluetooth devices.
In the BluetoothViewController.h file, declare a GKPeerPickerController object:
#import
"BluetoothViewController.h"
#import
@implementation
BluetoothViewController
@synthesize
currentSession;
@synthesize
txtMessage;
@synthesize
connect;
@synthesize
disconnect;
GKPeerPickerController
*picker;
The GKPeerPickerController class provides a standard UI to let your application
discover and connect to another Bluetooth device. This is the easiest way to
connect to another Bluetooth device.
To discover and connect to another
Bluetooth device, implement the btnConnect: method as follows:
-(IBAction)
btnConnect:(id) sender {
picker
= [[GKPeerPickerController alloc] init];
picker.delegate
= self;
picker.connectionTypesMask
= GKPeerPickerConnectionTypeNearby;
[connect
setHidden:YES];
[disconnect
setHidden:NO];
[picker
show];
}
- (void)peerPickerController:(GKPeerPickerController *)pickerdidConnectPeer:(NSString *)peerIDtoSession:(GKSession *) session {self.currentSession = session;session.delegate = self;[session setDataReceiveHandler:self withContext:nil];picker.delegate = nil;[picker dismiss];[picker autorelease];}If the user cancels the Bluetooth Picker, the peerPickerControllerDidCancel: method will be called. Define this method as follows:
- (void)peerPickerControllerDidCancel:(GKPeerPickerController *)picker{picker.delegate = nil;[picker autorelease];[connect setHidden:NO];[disconnect setHidden:YES];}To disconnect from a connected device, use the disconnectFromAllPeers method from the GKSession object. Define the btnDisconnect: method as follows:
-(IBAction) btnDisconnect:(id) sender {[self.currentSession disconnectFromAllPeers];[self.currentSession release];currentSession = nil;[connect setHidden:NO];[disconnect setHidden:YES];} - (void)session:(GKSession *)sessionpeer:(NSString *)peerIDdidChangeState:(GKPeerConnectionState)state {switch (state){case GKPeerStateConnected:NSLog(@"connected");break;case GKPeerStateDisconnected:NSLog(@"disconnected");[self.currentSession release];currentSession = nil;[connect setHidden:NO];[disconnect setHidden:YES];break;}}Sending Data
To send data to the connected Bluetooth device, use the sendDataToAllPeers: method of the GKSession object. The data that you send is transmitted via an NSData object; hence you are free to define your own application protocol to send any types of data (e.g. binary data such as images). Define the mySendDataToPeers: method as follows: - (void) mySendDataToPeers:(NSData *) data{if (currentSession)[self.currentSession sendDataToAllPeers:datawithDataMode:GKSendDataReliableerror:nil];} -(IBAction) btnSend:(id) sender{//---convert an NSString object to NSData---NSData* data;NSString *str = [NSString stringWithString:txtMessage.text];data = [str dataUsingEncoding: NSASCIIStringEncoding];[self mySendDataToPeers:data];}Receiving Data
- (void) receiveData:(NSData *)datafromPeer:(NSString *)peerinSession:(GKSession *)sessioncontext:(void *)context {//---convert the NSData to NSString---NSString* str;str = [[NSString alloc] initWithData:data encoding:NSASCIIStringEncoding];UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Data received"message:strdelegate:selfcancelButtonTitle:@"OK"otherButtonTitles:nil];[alert show];[alert release];}Testing the Application
You are now ready to test the application. Press Command-R in Xcode to deploy the application onto two iPhones / iPod Touches. For this article, I assume you have two devices -- either iPhones or iPod Touches. In order to run this application, they both need to run at least iPhone OS 3.0.
Once the application is deployed to the two devices, launch the application on both devices. On each device, tap the Connect button. The GKPeerPickerController will display the standard UI to discover other devices .
After a while, both application should be able to find each other When you tap on the name of the found device, the application will attempt to connect to it.
