FirstApp，iphone开发学习总结7，相机

首先需要一个Nav，在FirstAppAppDelegate.m里添加：

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    //...
    ImageViewController *imgTab = [[ImageViewController alloc] init];
    UINavigationController *navImg = [[UINavigationController alloc] initWithRootViewController:imgTab];//添加
    
    NSArray *tabArray = [[NSArray alloc] initWithObjects:navImg, tableTab, btnTab, textTab, navigation, nil];//修改
    [navImg release];//添加
    //...
}

进入ImageViewController.h文件，添加委托，并创建imageView变量：

@interface ImageViewController : UIViewController<UIImagePickerControllerDelegate, UINavigationControllerDelegate>{
    UIImageView *imageView;
}//UIImagePickerControllerDelegate继承至UINavigationControllerDelegate

ImageViewController.m的- viewDidLoad略做修改，并添加相机按钮：//直接使用UIBarButtonSystemItemCamera了

- (void)viewDidLoad
{
    imageView = [[UIImageView alloc] initWithFrame:CGRectMake(50.0, 50.0, 48.0, 48.0)];
    imageView.image = [UIImage imageNamed:@"China.gif"];
    imageView.contentMode = UIViewContentModeScaleAspectFit;
    [self.view addSubview:imageView];
    [imageView release];
        
    UIBarButtonItem *imgRightBtn = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemCamera target:self action:@selector(openCamera:)];
    [[self navigationItem] setRightBarButtonItem:imgRightBtn];
}

实现按钮事件：

- (void)openCamera:(id)sender
{
    UIImagePickerController *imagePicker = [[UIImagePickerController alloc] init];//initWithRootViewController:
    if ([UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypeCamera]) {
        [imagePicker setSourceType:UIImagePickerControllerSourceTypeCamera];
    }else {
        [imagePicker setSourceType:UIImagePickerControllerSourceTypePhotoLibrary];
    }
    [imagePicker setDelegate:self];
    [self presentModalViewController:imagePicker animated:YES];
    [imagePicker release];
}

 此处代码：

     isSourceTypeAvailable判定此设备是否支持相机，不然从图片目录获取图片。

     UIImagePickerController实例以模态展示，需要presentModalViewController它。

     souceType分别代表：Camera（打开相机），PhotoLibrary（打开相册），SavedPhotoAlbums（最近拍摄）

图片选择完成，则触发委托事件：

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info
{
    UIImage *image = [info objectForKey:UIImagePickerControllerOriginalImage];
    [imageView setImage:image];
    
    [self dismissModalViewControllerAnimated:YES];
}

 如果关闭了界面，则取消操作，触发：

imagePickerControllerDidCancel:

可以工作了，此处的一个问题就是当拍摄图片过大，内存警告回收资源，图片则不会显示。通过保存图片等操作解决，后面说。

求指点！