> For the complete documentation index, see [llms.txt](https://developers-apps-in-toss.toss.im/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://developers-apps-in-toss.toss.im/documentation/api-and-sdk-zh/sdk/shi-jian/graniteevent.md).

# graniteEvent

### 功能说明

订阅系统返回·Home 按钮事件。

* `backEvent` — 当发生 Android 返回等后退导航时
* `homeEvent` — 当返回首页时

### 类型

```ts
graniteEvent.addEventListener(
  event: "backEvent" | "homeEvent",
  args: { onEvent: () => void; onError?: (error: Error) => void },
): () => void;
```

**参数**

* `event` — 这是要订阅的事件。 `backEvent`(Android 返回键等后退导航), `homeEvent`（返回首页）之一。
* `args.onEvent: () => void` — 发生事件时会被调用。
* `args.onError?: (error: Error) => void` — 在订阅处理过程中发生错误时会被调用。

**响应**

返回取消订阅的函数 `() => void`。调用后会移除监听器。

### 示例代码

```js
import { graniteEvent } from "@apps-in-toss/web-framework";

const unsubscribe = graniteEvent.addEventListener("backEvent", {
  onEvent: () => {
    console.log("返回键触发");
  },
});

// 取消订阅
unsubscribe();
```


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