所谓激励广告，指的是用户可以选择与之互动来换取应用内奖励的一种广告。本指南介绍了如何将 AdMob 激励广告植入到 Flutter 应用中。
始终使用测试广告进行测试
在构建和测试应用时，请确保使用测试广告，而不是实际投放的广告。否则，可能会导致您的帐号被暂停。
对于激励广告，加载测试广告最简便的方法就是使用下面的测试专用广告单元 ID：
Android
ca-app-pub-3940256099942544/5224354917
iOS
ca-app-pub-3940256099942544/1712485313
测试广告单元配置为为每个请求返回测试广告，您可以在自己应用的编码、测试和调试过程中随意使用这些测试广告单元。只需确保在发布应用前用您自己的广告单元 ID 替换这些测试广告单元 ID 即可。
加载广告
以下示例加载了一个激励广告：
class RewardedExampleState extends State<RewardedExample> {
RewardedAd? _rewardedAd;
// TODO: replace this test ad unit with your own ad unit.
final adUnitId = Platform.isAndroid
? 'ca-app-pub-3940256099942544/5224354917'
: 'ca-app-pub-3940256099942544/1712485313';
/// Loads a rewarded ad.
void loadAd() {
RewardedAd.load(
adUnitId: adUnitId,
request: const AdRequest(),
adLoadCallback: RewardedAdLoadCallback(
// Called when an ad is successfully received.
onAdLoaded: (ad) {
debugPrint('$ad loaded.');
// Keep a reference to the ad so you can show it later.
_rewardedAd = ad;
},
// Called when an ad request failed.
onAdFailedToLoad: (LoadAdError error) {
debugPrint('RewardedAd failed to load: $error');
},
));
}
}
激励广告事件
通过使用 FullScreenContentCallback，您可以监听各种广告生命周期事件，例如广告何时展示或何时关闭。在展示广告之前设置 RewardedAd.fullScreenContentCallback，以接收这些事件的通知。以下示例实现了每个方法，并将消息记录到控制台：
class RewardedExampleState extends State<RewardedExample> {
RewardedAd? _rewardedAd;
// TODO: replace this test ad unit with your own ad unit.
final adUnitId = Platform.isAndroid
? 'ca-app-pub-3940256099942544/5224354917'
: 'ca-app-pub-3940256099942544/1712485313';
/// Loads a rewarded ad.
void loadAd() {
RewardedAd.load(
adUnitId: adUnitId,
request: const AdRequest(),
adLoadCallback: RewardedAdLoadCallback(
// Called when an ad is successfully received.
onAdLoaded: (ad) {
ad.fullScreenContentCallback = FullScreenContentCallback(
// Called when the ad showed the full screen content.
onAdShowedFullScreenContent: (ad) {},
// Called when an impression occurs on the ad.
onAdImpression: (ad) {},
// Called when the ad failed to show full screen content.
onAdFailedToShowFullScreenContent: (ad, err) {
// Dispose the ad here to free resources.
ad.dispose();
},
// Called when the ad dismissed full screen content.
onAdDismissedFullScreenContent: (ad) {
// Dispose the ad here to free resources.
ad.dispose();
},
// Called when a click is recorded for an ad.
onAdClicked: (ad) {});
debugPrint('$ad loaded.');
// Keep a reference to the ad so you can show it later.
_rewardedAd = ad;
},
// Called when an ad request failed.
onAdFailedToLoad: (LoadAdError error) {
debugPrint('RewardedAd failed to load: $error');
},
));
}
}
展示广告
RewardedAd 作为叠加层显示在所有应用内容之上，并以静态方式放置；因此，它无法添加到 Flutter widget 树。您可以通过调用 show() 来选择展示广告的时间。RewardedAd.show() 接受 OnUserEarnedRewardCallback，系统会在用户获得奖励时调用该方法。请务必实现此机制，并奖励观看广告的用户。
_rewardedAd.show(onUserEarnedReward: (AdWithoutView ad, RewardItem rewardItem) {
// Reward the user for watching an ad.
});
调用 show() 后，以这种方式展示的 Ad 无法以编程方式移除，并且需要用户输入。一个 RewardedAd 只能显示一次。后续显示的调用将触发 onAdFailedToShowFullScreenContent。
如果不再需要访问某个广告，则必须予以处置。调用 dispose() 的最佳实践是在 FullScreenContentCallback.onAdDismissedFullScreenContent 和 FullScreenContentCallback.onAdFailedToShowFullScreenContent 回调中进行。
大功告成！现在，您的应用就可以展示激励广告了。