UIImagePickerController 在关闭时复制内容

Question

当我调出一个 UIImagePickerController 然后关闭它时，它会复制我模态 window 中的内容。以下是前后对比图：

这是显示图像选择器的代码：

-(void) choosePhotos
{
    UIImagePickerController *imagePicker = [[UIImagePickerController alloc] init];

    [imagePicker setDelegate:self];
    [imagePicker setAllowsEditing:YES];
    [imagePicker setSourceType:UIImagePickerControllerSourceTypeCamera];

    [self presentViewController:imagePicker animated:YES completion:nil];
}

这是我的其余代码（如果需要）：

-(id) init
{
    self = [super init];

    if (self)
    {
        [self.navigationItem setTitle:@"Deposit"];

        UIBarButtonItem *closeButton = [[UIBarButtonItem alloc] initWithTitle:@"Cancel" style:UIBarButtonItemStyleDone target:self action:@selector(cancel)];
        [self.navigationItem setLeftBarButtonItem:closeButton];

        toItems = @[@"Account...5544", @"Account...5567"];

        UITapGestureRecognizer *recognizer = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(hideKeyboard)];
        [self.view addGestureRecognizer:recognizer];
    }

    return self;
}

-(void) hideKeyboard
{
    for (UITextField *field in [scrollView subviews])
    {
        [field resignFirstResponder];
    }
}

-(void) cancel
{
    [self.navigationController dismissViewControllerAnimated:YES completion:nil];
}

-(NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView
{
    return 1;
}

-(NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component
{
    return [toItems count];
}

-(NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component
{
    return [toItems objectAtIndex:row];
}

-(void) viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:YES];

    [self.view setBackgroundColor:[UIColor whiteColor]];

    UILabel *toLabel = [[UILabel alloc] initWithFrame:CGRectMake(20, 0, 50, 100)];
    [toLabel setText:@"To:"];

    toPicker = [[UIPickerView alloc] initWithFrame:CGRectMake(130, -30, 220, 100)];
    [toPicker setDataSource:self];
    [toPicker setDelegate:self];

    UILabel *amountLabel = [[UILabel alloc] initWithFrame:CGRectMake(20, 100, 70, 100)];
    amountLabel.lineBreakMode = NSLineBreakByWordWrapping;
    amountLabel.numberOfLines = 0;
    [amountLabel setText:@"Check Amount:"];

    UITextField *amountField = [[UITextField alloc] initWithFrame:CGRectMake(130, 100, 270, 100)];
    [amountField setPlaceholder:@"Enter Amount"];
    [amountField setReturnKeyType:UIReturnKeyDone];
    [amountField setKeyboardType:UIKeyboardTypeDecimalPad];

    UILabel *imagesLabel = [[UILabel alloc] initWithFrame:CGRectMake(20, 200, 70, 100)];
    imagesLabel.lineBreakMode = NSLineBreakByWordWrapping;
    imagesLabel.numberOfLines = 0;
    [imagesLabel setText:@"Check Images:"];

    UIButton *imagesButton = [[UIButton alloc] initWithFrame:CGRectMake(120, 200, 244, 99)];
    [imagesButton setBackgroundImage:[UIImage imageNamed:@"photos.png"] forState:UIControlStateNormal];
    [imagesButton addTarget:self action:@selector(choosePhotos) forControlEvents:UIControlEventTouchUpInside];

    CGRect bounds = [[UIScreen mainScreen] bounds];
    scrollView = [[UIScrollView alloc] initWithFrame:CGRectMake(0, 0, bounds.size.width, bounds.size.height)];
    [scrollView setAlwaysBounceVertical:YES];
    [scrollView setShowsVerticalScrollIndicator:YES];

    [scrollView addSubview:toLabel];
    [scrollView addSubview:toPicker];
    [scrollView addSubview:amountLabel];
    [scrollView addSubview:amountField];
    [scrollView addSubview:imagesLabel];
    [scrollView addSubview:imagesButton];

    [self.view addSubview:scrollView];
}

Answer 1

每次调用 viewWillAppear 时，您的 UI 元素都会添加到您的视图中。当您的图像选择器关闭并 returns 到您的视图时调用，因此它们被复制。在再次创建它们之前检查您的 UI 元素是否已经存在，或者在 viewDidLoad 方法中进行 UI 设置，该方法只会运行一次。您或许可以试试这个，使用 BOOL 属性来跟踪：

-(void) viewWillAppear:(BOOL)animated
{

  [super viewWillAppear:YES];

  if (!self.alreadyAppeared) {
      self.alreadyAppeared = YES;
      // Create labels and buttons
  }
}

Answer 2

我建议您使用 viewDidLoad 作为创建和添加视图的地方：

- (void)viewDidLoad {
    [super viewDidLoad];
    //init and add your views here
    //example view
    self.someLabel = [[UILabel alloc] init];
    self.someLabel.text = @"someExampleText";
    [self.view addSubview:self.someLabel];
}

并且 viewWillAppear 或 viewDidLayoutSubviews 作为配置它们大小的地方（我更喜欢 viewDidLayoutSubviews 所以我会用它作为例子）：

- (void)viewDidLayoutSubviews {
    [super viewDidLayoutSubviews];
    self.someLabel.frame = CGRectMake(kMargin,kMargin,kLabelWidth,kLabelHeight);
}

当然，为了做到这一点，您需要通过在界面中为它们创建属性来引用您希望以这种方式配置的所有视图：

@interface YourViewController ()

@property (nonatomic, strong) UILabel *someLabel;

@end;

static CGFloat const kMargin = 20.0f;
static CGFloat const kLabelHeight = 30.0f;
static CGFloat const kLabelWidth = 100.0f;

此外，建议您避免使用硬编码值作为它们的大小（像 CGRectMake(20,20,100,70) 那样做，但这并不是完全错误的。

不使用硬编码值并不意味着要自己设置它们，它只是意味着使它们的值更具可读性（并且在大多数情况下是动态的）。在我的示例中，我创建了 kMargin、kLabelHeight 和 kLabelWidth，这意味着任何查看此代码的人都会理解它们的意思，他们会知道在需要时要更改什么，以及这些值可以用在其他地方。

例如，您可以有 4 个标签，为了让它们都遵循相同的布局规则，它们都将使用 origin.x 上的 kMargin 值。

您也可以实现一个动态值，而不是使用宽度的静态值，如下所示：

 - (void)viewDidLayoutSubviews {
    [super viewDidLayoutSubviews];
    CGFloat labelWidth = self.view.bounds.size.width - (kMargin * 2);
    self.someLabel.frame = CGRectMake(kMargin,kMargin,labelWidth,kLabelHeight);
}

我在这里所做的是使我的标签具有与我的超级视图相同的宽度，但我让它考虑了左右边距（通过获取总视图宽度并减少两倍边距值） .

由于我们在 viewDidLayoutSubviews 方法上执行此操作，每当父视图更改其大小（例如，方向更改）时都会调用该方法，这将确保您的 UILabel 可以在任何大小的视图和方向上显示没有额外的代码来处理 'specific cases'.

UIImagePickerController 在关闭时复制内容

UIImagePickerController duplicates content on close

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uiimagepickercontroller

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