如何判断cameraDevice是否可用？

Question

在我当前的应用程序中，我允许用户向在线图像服务提交图像。我允许用户从他们的相册中选择或者用相机拍照。

然而，我有一个问题。如果正在使用的设备没有摄像头，而用户选择拍照，应用程序就会崩溃。我需要能够确定设备是否能够使用cameraDevice。

下面是我当前的代码，用于呈现一个UIActionSheet，它允许用户选择不同的选项。

#pragma mark -
#pragma mark UIImagePickerController
- (IBAction)ImagePicker {
UIActionSheet *sheet = [[UIActionSheet alloc] 
                        initWithTitle:@"" delegate:self 
                        cancelButtonTitle:@"Cancel" 
                        destructiveButtonTitle:nil 
                        otherButtonTitles:@"Choose An Existing Photo", @"Take A Photo", nil];
sheet.actionSheetStyle = UIActionSheetStyleDefault;
[sheet showInView:self.view];
[sheet release];
}

- (void)actionSheet:(UIActionSheet *)actionSheet clickedButtonAtIndex:(NSInteger)buttonIndex {

if (buttonIndex == 0) {
    //Okay the UIImagePickerControllerSourceTypeSavedPhotosAlbum displays the 
    NSLog(@"Album");
    UIImagePickerController *picker = [[UIImagePickerController alloc] init];
    picker.delegate = self;
    picker.sourceType = UIImagePickerControllerSourceTypeSavedPhotosAlbum;
    [self presentModalViewController:picker animated:YES];
    [picker release];

} else if (buttonIndex == 1) {
    NSLog(@"Camera");
    UIImagePickerController *picker = [[UIImagePickerController alloc] init];
    picker.delegate = self;
    picker.sourceType = UIImagePickerControllerSourceTypeCamera;
    [self presentModalViewController:picker animated:YES];
    [picker release];
}
}

提前感谢！

Answer 1

if (![UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypeCamera]) { NSLog(@"No camera!"); }

Answer 2

类似这样的东西也可以工作：

NSString* b1 = @"Get from album";
NSString* b2 = nil;

BOOL cameraAvailable = [UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypeCamera];

if ( cameraAvailable ) {
     b2 = @"Take a photo";   
}

UIActionSheet * sheet = [[UIActionSheet alloc] initWithTitle: alertTitle
                                                    delegate: self
                                           cancelButtonTitle: @"Cancel"
                                      destructiveButtonTitle: nil
                                           otherButtonTitles: b1, b2, nil];         
[sheet showInView: self.view];
[sheet release];

Answer 3

我不会忘记，我必须添加标签和一个新属性，一个名为UIActionSheet的工作表。下面的代码是我如何让一切都工作的，绝对无缝的。

#pragma mark -
#pragma mark UIImagePickerController
- (IBAction)ImagePicker {

if (![UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypeCamera]) {
sheet = [[UIActionSheet alloc] 
                        initWithTitle:@"" delegate:self 
                        cancelButtonTitle:@"Cancel" 
                        destructiveButtonTitle:nil 
                        otherButtonTitles:@"Choose An Existing Photo", nil];
sheet.actionSheetStyle = UIActionSheetStyleDefault;
[sheet showInView:self.view];
sheet.tag = 0;
[sheet release];
}

else {
    sheet = [[UIActionSheet alloc] 
                            initWithTitle:@"" delegate:self 
                            cancelButtonTitle:@"Cancel" 
                            destructiveButtonTitle:nil 
                            otherButtonTitles:@"Choose An Existing Photo", @"Take A Photo", nil];
    sheet.actionSheetStyle = UIActionSheetStyleDefault;
    [sheet showInView:self.view];
    sheet.tag = 1;
    [sheet release];
}

}

- (void)actionSheet:(UIActionSheet *)actionSheet clickedButtonAtIndex:(NSInteger)buttonIndex {

switch (sheet.tag) {
    case 0:
        if (buttonIndex == 0) {
            //Okay the UIImagePickerControllerSourceTypeSavedPhotosAlbum displays the 
            NSLog(@"Album");
            UIImagePickerController *picker = [[UIImagePickerController alloc] init];
            picker.delegate = self;
            picker.sourceType = UIImagePickerControllerSourceTypeSavedPhotosAlbum;
            [self presentModalViewController:picker animated:YES];
            [picker release];

        }
        break;
    case 1:
        if (buttonIndex == 0) {
            //Okay the UIImagePickerControllerSourceTypeSavedPhotosAlbum displays the 
            NSLog(@"Album");
            UIImagePickerController *picker = [[UIImagePickerController alloc] init];
            picker.delegate = self;
            picker.sourceType = UIImagePickerControllerSourceTypeSavedPhotosAlbum;
            [self presentModalViewController:picker animated:YES];
            [picker release];

        } else if (buttonIndex == 1) {
            NSLog(@"Camera");
            UIImagePickerController *picker = [[UIImagePickerController alloc] init];
            picker.delegate = self;
            picker.sourceType = UIImagePickerControllerSourceTypeCamera;
            [self presentModalViewController:picker animated:YES];
            [picker release];
        }
        break;
}
}