1. PurchasesResult：表示购买结果的类，其中包含了购买的详细信息，如订单ID、商品ID、支付时间等。

2. queryPurchases：查询购买信息的方法，可以返回用户已购买的商品信息列表。

示例代码：

private void queryPurchases() {
    Purchase.PurchasesResult purchasesResult = mBillingClient.queryPurchases(BillingClient.SkuType.INAPP);
    if (purchasesResult.getResponseCode() == BillingClient.BillingResponse.OK && purchasesResult.getPurchasesList() != null) {
        handlePurchases(purchasesResult.getPurchasesList());
    }
}

3. getPurchasesList：获取购买信息列表的方法，返回一个List，其中包含了用户已购买的商品信息。

示例代码：

private void handlePurchases(List purchases) {
    for (Purchase purchase : purchases) {
        if (purchase.getSku().equals(PRODUCT_ID)) {
            // 处理购买成功逻辑
        }
    }
}

4. getSku：获取商品ID的方法，返回一个String，表示商品的唯一标识符。

示例代码：

private void startPayment() {
    List skuList = new ArrayList<>();
    skuList.add(PRODUCT_ID);
    SkuDetailsParams params = SkuDetailsParams.newBuilder().setSkusList(skuList).setType(BillingClient.SkuType.INAPP).build();
    mBillingClient.querySkuDetailsAsync(params, new SkuDetailsResponseListener() {
        @Override
        public void onSkuDetailsResponse(BillingResult billingResult, List skuDetailsList) {
            if (billingResult.getResponseCode() == BillingClient.BillingResponse.OK && skuDetailsList != null && !skuDetailsList.isEmpty()) {
                SkuDetails skuDetails = skuDetailsList.get(0);
                BillingFlowParams flowParams = BillingFlowParams.newBuilder().setSkuDetails(skuDetails).build();
                int responseCode = mBillingClient.launchBillingFlow(activity, flowParams).getResponseCode();
                if (responseCode != BillingClient.BillingResponse.OK) {