Ios UIScrollView的所有图像都放在开头

我不熟悉iOS编程。我希望使用编码生成所有控件，然后应用约束以实现自动调整大小功能。我几乎达到了我的要求，除了一个问题，那就是我的UIScrollView的所有图像都被放置在最开始的位置，而UIScrollView的其余部分保持为空。我想我的约束条件有些问题，目前我无法解决。 这是我的密码

self.bgView.image = [UIImage imageNamed:@"bg.png"];

NSDictionary *viewDictionary = @{@"bgImage":self.bgView,@"scrollView":self.scrollView};

NSDictionary *position = @{@"vSpacing":@0,@"hSpacing":@0};

//here I had specified the size of the background image corresponding to the view

NSArray *constraint_POS_H = [NSLayoutConstraint constraintsWithVisualFormat:@"H:|-hSpacing-[bgImage]-hSpacing-|" options:0 metrics:position views:viewDictionary];

NSArray *constraint_POS_V = [NSLayoutConstraint constraintsWithVisualFormat:@"V:|-vSpacing-[bgImage]-vSpacing-|" options:0 metrics:position views:viewDictionary];

[self.view addConstraints:constraint_POS_H];

[self.view addConstraints:constraint_POS_V];



    //here I am specifying the size of scroll view
    [self.view addConstraint:[NSLayoutConstraint
                              constraintWithItem:self.scrollView
                              attribute:NSLayoutAttributeWidth
                              relatedBy:NSLayoutRelationGreaterThanOrEqual
                              toItem:self.bgView
                              attribute:NSLayoutAttributeWidth
                              multiplier:1.0
                              constant:0.0]];

    [self.view addConstraint:[NSLayoutConstraint
                              constraintWithItem:self.scrollView
                              attribute:NSLayoutAttributeHeight
                              relatedBy:NSLayoutRelationEqual
                              toItem:self.bgView
                              attribute:NSLayoutAttributeHeight
                              multiplier:0.5
                              constant:0.0]];


    [self.view addConstraint:[NSLayoutConstraint
                              constraintWithItem:self.scrollView
                              attribute:NSLayoutAttributeCenterX
                              relatedBy:NSLayoutRelationEqual
                              toItem:self.bgView
                              attribute:NSLayoutAttributeCenterX
                              multiplier:1.0
                              constant:0.0]];

    [self.view addConstraint:[NSLayoutConstraint
                              constraintWithItem:self.scrollView
                              attribute:NSLayoutAttributeCenterY
                              relatedBy:NSLayoutRelationEqual
                              toItem:self.bgView
                              attribute:NSLayoutAttributeCenterY
                              multiplier:1.0
                              constant:0.0]];





    //self.view.autoresizesSubviews = YES;
    self.scrollView.pagingEnabled = YES;
    NSInteger numberOfViews = photoArray.count;
    for (int i=0; i < numberOfViews; i++) {
        CGFloat myOrigin = i * self.view.frame.size.width;
        NSLog(@"self.view.frame.size.width : %f",self.view.frame.size.width);
        UIView *myView = [[UIView alloc]initWithFrame:CGRectMake(myOrigin, 0, self.view.frame.size.width, self.scrollView.frame.size.height)];

        [myView setTranslatesAutoresizingMaskIntoConstraints:NO];
        [self.view addSubview:myView];
        //here I am specifying the size of uiview
      [self.view addConstraint:[NSLayoutConstraint
                                  constraintWithItem:myView
                                  attribute:NSLayoutAttributeWidth
                                  relatedBy:NSLayoutRelationGreaterThanOrEqual
                                  toItem:self.scrollView
                                  attribute:NSLayoutAttributeWidth
                                  multiplier:1.0
                                  constant:0.0]];
        [self.view addConstraint:[NSLayoutConstraint
                                  constraintWithItem:myView
                                  attribute:NSLayoutAttributeHeight
                                  relatedBy:NSLayoutRelationEqual
                                  toItem:self.scrollView
                                  attribute:NSLayoutAttributeHeight
                                  multiplier:1.0
                                  constant:0.0]];

        //here I am specifying the position of uiview
         [self.view addConstraint:[NSLayoutConstraint
                                  constraintWithItem:myView
                                  attribute:NSLayoutAttributeCenterX
                                  relatedBy:NSLayoutRelationEqual
                                  toItem:self.scrollView
                                  attribute:NSLayoutAttributeCenterX
                                  multiplier:1.0
                                  constant:0.0]];
        [self.view addConstraint:[NSLayoutConstraint
                                  constraintWithItem:myView
                                  attribute:NSLayoutAttributeCenterY
                                  relatedBy:NSLayoutRelationEqual
                                  toItem:self.scrollView
                                  attribute:NSLayoutAttributeCenterY
                                  multiplier:1.0
                                  constant:0.0]];

        UIImageView *photos = [[UIImageView alloc]initWithFrame:CGRectMake(0, 0, myView.frame.size.width, self.scrollView.frame.size.height)];
        //self.photos = [UIImageView new];
        [photos setTranslatesAutoresizingMaskIntoConstraints:NO];

        photos.image = [photoArray objectAtIndex:i];
        [myView addSubview:photos];
        //here I am specifying the size of image view within scroll view
           [self.view addConstraint:[NSLayoutConstraint
                                  constraintWithItem:photos
                                  attribute:NSLayoutAttributeWidth
                                  relatedBy:NSLayoutRelationLessThanOrEqual
                                  toItem:myView
                                  attribute:NSLayoutAttributeWidth
                                  multiplier:1.0
                                  constant:0.0]];
        [self.view addConstraint:[NSLayoutConstraint
                                  constraintWithItem:photos
                                  attribute:NSLayoutAttributeHeight
                                  relatedBy:NSLayoutRelationEqual
                                  toItem:self.scrollView
                                  attribute:NSLayoutAttributeHeight
                                  multiplier:1.0
                                  constant:0.0]];

        //here I am specifying the position of the image view
        [self.view addConstraint:[NSLayoutConstraint
                                  constraintWithItem:photos
                                  attribute:NSLayoutAttributeCenterX
                                  relatedBy:NSLayoutRelationEqual
                                  toItem:self.scrollView
                                  attribute:NSLayoutAttributeCenterX
                                  multiplier:1.0
                                  constant:0.0]];
        [self.view addConstraint:[NSLayoutConstraint
                                  constraintWithItem:photos
                                  attribute:NSLayoutAttributeCenterY
                                  relatedBy:NSLayoutRelationEqual
                                  toItem:myView
                                  attribute:NSLayoutAttributeCenterY
                                  multiplier:1.0
                                  constant:0.0]];






        self.scrollView.delegate = self;
        [self.scrollView addSubview:myView];
        NSLog(@"self.myView.frame.size.width : %f",myView.frame.size.width);

    }

    self.scrollView.contentSize = CGSizeMake(self.view.frame.size.width * numberOfViews,
                                             self.scrollView.frame.size.height);
    CGPoint scrollPoint = CGPointMake(0, 0);
   [self.scrollView setContentOffset:scrollPoint animated:YES];

    [self.view addSubview:self.scrollView];

self.bgView.image=[UIImage ImageName:@“bg.png”]；
NSDictionary*viewDictionary=@{@“bgImage”：self.bgView，@“scrollView”：self.scrollView}；
NSDictionary*position=@{@“vSpacing”：@0，@“hSpacing”：@0}；
//在这里，我指定了与视图对应的背景图像的大小
NSArray*constraint_POS_H=[NSLayoutConstraint Constraints With VisualFormat:@“H:|-hSpacing-[bgImage]-hSpacing-|”选项：0度量：位置视图：viewDictionary]；
NSArray*constraint_POS_V=[NSLayoutConstraint Constraints With VisualFormat:@“V:|-VSPACGE-[bgImage]-VSPACGE-|”选项：0度量：位置视图：viewDictionary]；
[self.view addConstraints:constraint_POS_H]；
[self.view addConstraints:constraint_POS_V]；
//这里我指定了滚动视图的大小
[self.view addConstraint:[NSLayoutConstraint]
constraintWithItem:self.scrollView
属性：NSLAYUTATTRIBUTEWIDTH
相关方：NSLAYOUT相关性大于或等于
toItem:self.bgView
属性：NSLAYUTATTRIBUTEWIDTH
乘数：1.0
常数：0.0]]；
[self.view addConstraint:[NSLayoutConstraint]
constraintWithItem:self.scrollView
属性：NSLayoutAttributeHeight
关系人：NSLayoutRelationEqual
toItem:self.bgView
属性：NSLayoutAttributeHeight
乘数：0.5
常数：0.0]]；
[self.view addConstraint:[NSLayoutConstraint]
constraintWithItem:self.scrollView
属性：nsLayoutAttributeCenter
关系人：NSLayoutRelationEqual
toItem:self.bgView
属性：nsLayoutAttributeCenter
乘数：1.0
常数：0.0]]；
[self.view addConstraint:[NSLayoutConstraint]
constraintWithItem:self.scrollView
属性：nsLayoutAttributeCenter
关系人：NSLayoutRelationEqual
toItem:self.bgView
属性：nsLayoutAttributeCenter
乘数：1.0
常数：0.0]]；
//self.view.autoresizesSubviews=是；
self.scrollView.paginEnabled=是；
NSInteger numberOfViews=photoArray.count；
对于（int i=0；i