I've been working on a number of iPhone camera applications. The default photograph functionality seemed kind of awkward to me, and I wanted to have a much simpler process and interface. This is an example of an Xcode project which shows how to load the camera interface with a custom overlaid image, and then wait for a tap anywhere on the screen to take a photo.
To start, I created a new project (a View-based application) called CameraTapper.
I knew I would need to subclass UIImagePickerController, but there's really not much I needed to over-ride. I created a new file (with UIView as a base) called CustomCamera.m (and .h) and then modified them to support the "tap anywhere to capture" functionality:
#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>
@interface CustomCamera : UIImagePickerController {
}
@end
#import "CustomCamera.h"
@implementation CustomCamera
-(void) dealloc {
[super dealloc];
}
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
// override the touches ended method
// so tapping the screen will take a picture
[self takePicture];
}
- (void)viewDidDisappear:(BOOL)animated {
[super viewDidDisappear:animated];
}
-(void) viewDidAppear: (BOOL)animated {
[super viewDidAppear:animated];
}
@end
I also added an overlay to the project (a 24 bit transparent png):
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| Multi-Value Specifier |
This article will give you a good understanding of how to communicate with XML web services from within your iPhone application, and the examples will provide a solid foundation for consuming other web services in your own projects.
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| Figure 1. IPToCountry Web Service: This web service exposes two web methods. | |
Before beginning an Xcode project to consume a web service, examining a real web service to see the different ways you can consume is worthwhile. My favorite example is to use an ASMX XML web service created using .NET. For discussion purposes, here's a look at a web service called IPToCountry, which lets you supply an IP address and returns the country to which the IP address belongs.
The IPToCountry web service is located at http://www.ecubicle.net/iptocountry.asmx. If you use Safari to load this URL, you'll see that it exposes two web methods as shown in Figure 1.
As an example, the FindCountryAsXML returns the result (the country) as an XML string. Clicking the FindCountryAsXML link reveals the page shown in Figure 2.
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| Figure 2. FindCountryAsXml Service: Testing the web service through a browser interface shows the XML packets exchanged between the client and the server. | |
The important parts are the sections following the Test section of the page. They detail the various ways in which you can consume the web service. In the .NET world, accessing the web service is a pretty straightforward affair—Visual Studio provides a built-in tool that automatically creates a web proxy service object for the web service when you download the WSDL document. For iPhone development, you need to get your hands dirty, so it's far more important to understand the underlying mechanics of consuming web services.
One way to consume this web service is to use SOAP (Simple Object Access Protocol). When using SOAP, you use the HTTP POST method to send a request to the web service, as shown in the following example:
POST /iptocountry.asmx HTTP/1.1
Host: www.ecubicle.net
Content-Type: text/xml; charset=utf-8
Content-Length: length
SOAPAction: "http://www.ecubicle.net/webservices/FindCountryAsXml"
<?xml version="1.0" encoding="utf-8"?>
<soap:Envelope xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:xsd="http://www.w3.org/2001/XMLSchema"
xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
<soap:Body>
<FindCountryAsXml xmlns="http://www.ecubicle.net/webservices/">
<V4IPAddress>string</V4IPAddress>
</FindCountryAsXml>
</soap:Body>
</soap:Envelope>
The parts of the code in bold are the placeholders where you need to substitute the actual values. A couple of important things to note from the above:
<?xml version="1.0" encoding="utf-8"?>
<soap:Envelope xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:xsd="http://www.w3.org/2001/XMLSchema"
xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
<soap:Body>
<FindCountryAsXml xmlns="http://www.ecubicle.net/webservices/">
<V4IPAddress>string</V4IPAddress>
</FindCountryAsXml>
</soap:Body>
</soap:Envelope>
The web service will return a response formatted as follows:
HTTP/1.1 200 OK
Content-Type: text/xml; charset=utf-8
Content-Length: length
<?xml version="1.0" encoding="utf-8"?>
<soap:Envelope xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:xsd="http://www.w3.org/2001/XMLSchema"
xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
<soap:Body>
<FindCountryAsXmlResponse
xmlns="http://www.ecubicle.net/webservices/">
<FindCountryAsXmlResult>xml result</FindCountryAsXmlResult>
</FindCountryAsXmlResponse>
</soap:Body>
</soap:Envelope>
For a real request, the result (the country) will be enclosed within the block of XML code (the bold placeholder in the preceding example). You would need to extract it from the XML result.