Filter4Cam 實作: 2. 建立助手類別

since: 2012/02/23
update: 2012/02/27
reference: The iOS 5 Developer's Cookbook

A. 建立助手類別
     Xcode > File > New > New File...
     iOS > Cocoa Touch > Objective-C class > Next
     Class: Filter4CamHelper
     Subclass of: NSObject
     > Next > Create

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B. 查詢與取得相機     
     1. 開啓 Filter4CamHelper.h 檔案, 修改如下:
#import <Foundation/Foundation.h>
//@add
#import <AVFoundation/AVFoundation.h>

@interface Filter4CamHelper : NSObject
{

}

//@add for Available Cameras
+ (int)numberOfCameras; // 相機的數目
+ (BOOL)backCameraAvailable; // 後置相機是否可用
+ (BOOL)frontCameraAvailable; // 前置相機是否可用
+ (AVCaptureDevice *)backCamera; // 後置相機
+ (AVCaptureDevice *)frontCamera; // 前置相機

@end

     2. 開啓 Filter4CamHelper.m 檔案, 修改如下:
#import "Filter4CamHelper.h"

#pragma mark Filter4Cam Helper

@implementation Filter4CamHelper

//@add for Available Cameras
#pragma mark Available Cameras

//@add:相機的數目
+ (int)numberOfCameras
{
    return [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo].count;
}

//@add:後置相機是否可用
+ (BOOL)backCameraAvailable
{
    NSArray *videoDevices = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];

    for (AVCaptureDevice *device in videoDevices)
        if (device.position == AVCaptureDevicePositionBack) return YES;

    return NO;
}

//@add:前置相機是否可用
+ (BOOL)frontCameraAvailable
{
    NSArray *videoDevices = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];

    for (AVCaptureDevice *device in videoDevices)
        if (device.position == AVCaptureDevicePositionFront) return YES;

    return NO;
}

//@add:後置相機
+ (AVCaptureDevice *)backCamera
{
    NSArray *videoDevices = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];

    for (AVCaptureDevice *device in videoDevices)
        if (device.position == AVCaptureDevicePositionBack) return device;
   
    return [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
}

//@add:前置相機
+ (AVCaptureDevice *)frontCamera
{
    NSArray *videoDevices = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];

    for (AVCaptureDevice *device in videoDevices)
        if (device.position == AVCaptureDevicePositionFront) return device;
   
    return [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
}

@end  

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C. 測試
    1. 開啓 ViewController.h 檔案, 修改如下:
#import <UIKit/UIKit.h>
#import <GLKit/GLKit.h>
//@add
#import "Filter4CamHelper.h"
....

//@add for test
- (void)helperTest;

@end

    2. 開啓 ViewController.m 檔案, 修改如下:
#import "ViewController.h"
....

#pragma mark Test
//@add
- (void)helperTest
{
    NSLog(@"numberOfCameras = %d", [Filter4CamHelper numberOfCameras]);

    NSLog(@"backCameraAvailable = %@", [Filter4CamHelper backCameraAvailable] ? @"YES" : @"NO");

    NSLog(@"frontCameraAvailable = %@", [Filter4CamHelper frontCameraAvailable] ? @"YES" : @"NO");
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    //@add:helper Test
    [self helperTest];}
....

    2. 編譯並執行:

    3. 備註:
        如果部署到實機測試時發生問題, 請檢查 "佈建描述檔" 是否過於雜亂,
        可以將其刪除.
         iOS Device > 設定 > 一般 > 描述檔: