# 在 iOS 中实现横幅广告

> 在 iOS 应用中实现横幅广告。在 View 层级视图中创建和显示横幅广告视图对象，并使用委托来管理广告事件。

> **Important:**
>
> app-ads.txt 是一个 IAB 倡议文件，旨在打击欺诈，建立透明的广告生态系统。请务必按照要求实现 app-ads.txt。否则，横幅广告需求可能会显著下降。

横幅广告需要特定类型的专用横幅广告单元。

您可以将横幅广告视图对象放入 View 层级视图中，就像放置任何其他视图一样。这样就可以自定义每个横幅广告实例的位置，或显示多个横幅广告。

> **Note:**
>
> 如 [Apple 指南](https://developer.apple.com/documentation/uikit/uiview/positioning_content_relative_to_the_safe_area)中所述，横幅广告的内容不会在安全区域之外呈现。

## 脚本实现##script-implementation

将您的横幅广告代码添加到 `ViewController` 实现 (`.m`) 中。以下脚本示例是用于在屏幕上展示两个横幅广告的示例实现方案。如需了解引用的类的更多信息，请参阅 [`UADSBannerView`](/grow/ads/ios-sdk/ios-api.md#uadsbannerview) API 部分。

### 实现 MREC 横幅广告格式##implementing-the-mrec-banner-format

> **Note:**
>
> 在展示横幅广告之前必须初始化 Unity Ads。

要在应用中显示中等矩形 (MREC) 大小的广告格式，请确保使用适当的尺寸，例如 300x250、300x300 或 450x450。如果使用的是 300x250 的 MREC 横幅广告，将它替换为以下示例代码：

```objective-c
CGSizeMake(320, 50)
```

调整后的尺寸：

```objective-c
CGSizeMake(300, 250)
```

#### 横幅广告示例##banner-ad-example

1. **Objective-C**

   ```objective-c
   @interface ViewController () <UADSBannerViewDelegate>
   ​​
   // This is the Ad Unit or Placement that will display banner ads: 
   @property (strong) NSString* placementId;
   // This banner view object will be placed at the top of the screen: 
   @property (strong, nonatomic) UADSBannerView *topBannerView;
   // This banner view object will be placed at the bottom of the screen: 
   @property (strong, nonatomic) UADSBannerView *bottomBannerView;
   ​​
   @end
   ​​
   @implementation ViewController
   ​​
   - (void)viewDidLoad {
       [super viewDidLoad];
       self.placementId = @"banner";
       [UnityAds initialize: @"1234567" testMode: YES initializationDelegate: self];
   }
   ​​
   // Example method for creating and loading the top banner view object: 
   - (void)loadTopBanner{
       // Instantiate a banner view object with the Ad Unit ID and size: 
       self.topBannerView = [[UADSBannerView alloc] initWithPlacementId：_placementId size：CGSizeMake(320, 50)];
       // Set the banner delegate for event callbacks: 
       self.topBannerView.delegate = self;
       // Add the banner view object to the view hierarchy: 
       [self addBannerViewToTopView:self.topBannerView];
       // 将广告内容加载到横幅视图对象：
       [_topBannerView load];
   }
   ​​
   // Example method for creating and loading the bottom banner view object: 
   - (void)loadBottomBanner{
       self.bottomBannerView = [[UADSBannerView alloc] initWithPlacementId：_placementId size：CGSizeMake(320, 50)];
       self.bottomBannerView.delegate = self;
       [self addBannerViewToBottomView:self.bottomBannerView];
       [_bottomBannerView load];
   }
   ​​
   // Example method for discarding the top banner view object (for example, if there's no fill): 
   - (void)unLoadTopBanner{
       // Remove the banner view object from the view hierarchy: 
       [self.topBannerView removeFromSuperview];
       // Set it to nil: 
       _topBannerView = nil;
   }
   ​​
   // Example method for discarding the bottom banner view object: 
   - (void)unLoadBottomBanner{
       [self.bottomBannerView removeFromSuperview];
       _bottomBannerView = nil;
   }
   ​​

   ​// Example method for placing the top banner view object: 
   - (void)addBannerViewToTopView:(UIView *)bannerView {
       bannerView.translatesAutoresizingMaskIntoConstraints = NO;
       [self.view addSubview:bannerView];
       [self.view addConstraints:@[
           [NSLayoutConstraint constraintWithItem:bannerView
                                       attribute:NSLayoutAttributeTop
                                       relatedBy:NSLayoutRelationEqual
                                           toItem:self.topLayoutGuide
                                       attribute:NSLayoutAttributeBottom
                                       multiplier:1
                                         constant:0],
           [NSLayoutConstraint constraintWithItem:bannerView
                                       attribute:NSLayoutAttributeCenterX
                                       relatedBy:NSLayoutRelationEqual
                                           toItem:self.view
                                       attribute:NSLayoutAttributeCenterX
                                       multiplier:1
                                         constant:0]
       ]];
   }

   ​// Example method for placing the bottom banner view object:
   - (void)addBannerViewToBottomView: (UIView *)bannerView {
       bannerView.translatesAutoresizingMaskIntoConstraints = NO;
       [self.view addSubview:bannerView];
       [self.view addConstraints:@[
           [NSLayoutConstraint constraintWithItem:bannerView
                                       attribute:NSLayoutAttributeBottom
                                       relatedBy:NSLayoutRelationEqual
                                           toItem:self.bottomLayoutGuide
                                       attribute:NSLayoutAttributeTop
                                       multiplier:1
                                         constant:0],
           [NSLayoutConstraint constraintWithItem:bannerView
                                       attribute:NSLayoutAttributeCenterX
                                       relatedBy:NSLayoutRelationEqual
                                           toItem:self.view
                                       attribute:NSLayoutAttributeCenterX
                                       multiplier:1
                                         constant:0]
       ]];
   }

   ​// Implement the delegate methods:
   #pragma mark :UADSBannerViewDelegate

   - (void)bannerViewDidLoad:(UADSBannerView *)bannerView {
       // Called when the banner view object finishes loading an ad.
       NSLog(@"Banner loaded for Ad Unit or Placement: %@", bannerView.placementId);
   }

   - (void)bannerViewDidClick:(UADSBannerView *)bannerView {
       // Called when the banner is clicked.
       NSLog(@"Banner was clicked for Ad Unit or Placement: %@", bannerView.placementId);
   }

   - (void)bannerViewDidLeaveApplication:(UADSBannerView *)bannerView {
       // Called when the banner links out of the application.
   }


   - (void)bannerViewDidError:(UADSBannerView *)bannerView error:(UADSBannerError *)error{
       // Called when an error occurs showing the banner view object.
       NSLog(@"Banner encountered an error for Ad Unit or Placement: %@ with error message %@", bannerView.placementId, [error localizedDescription]);
       // Note that the UADSBannerError can indicate no fill (refer to the API documentation).
   }
   @end
   ```

**后续步骤**：查看[变现策略](/grow/ads/monetization-strategy.md)指南并[测试您的实现](/grow/ads/optimization/test-ads-integration.md)。