通过 Bluez DBus API 的设备连接/断开通知

Question

如何在通过 bluez dbus API 创建或销毁连接时接收信号或通知？

在 /org/bluez/hci0 下的所有设备中轮询 Connected() 有效，但恕我直言，这不是一种有效的方式。

Answer 1

您需要在org.bluez.Device1 接口上监听PropertiesChanged 信号。我没有直接的设备接口示例，但模板如下，

static void bluez_signal_device_changed(GDBusConnection *conn,
                    const gchar *sender,
                    const gchar *path,
                    const gchar *interface,
                    const gchar *signal,
                    GVariant *params,
                    void *userdata)
{
    (void)conn;
    (void)sender;
    (void)path;
    (void)interface;
    (void)userdata;

    GVariantIter *properties = NULL;
    GVariantIter *unknown = NULL;
    const char *iface;
    const char *key;
    GVariant *value = NULL;
    const gchar *signature = g_variant_get_type_string(params);

    if(strcmp(signature, "(sa{sv}as)") != 0) {
        g_print("Invalid signature for %s: %s != %s", signal, signature, "(sa{sv}as)");
        goto done;
    }

    g_variant_get(params, "(&sa{sv}as)", &iface, &properties, &unknown);
    while(g_variant_iter_next(properties, "{&sv}", &key, &value)) {
        if(!g_strcmp0(key, "Connected")) {
            if(!g_variant_is_of_type(value, G_VARIANT_TYPE_BOOLEAN)) {
                g_print("Invalid argument type for %s: %s != %s", key,
                        g_variant_get_type_string(value), "b");
                goto done;
            }
            g_print("Device is \"%s\"\n", g_variant_get_boolean(value) ? "Connected" : "Disconnected");
        }
    }
done:
    if(properties != NULL)
        g_variant_iter_free(properties);
    if(value != NULL)
        g_variant_unref(value);
}


GDBusConnection *con = g_bus_get_sync(G_BUS_TYPE_SYSTEM, NULL, NULL);
prop_changed = g_dbus_connection_signal_subscribe(con,
                    "org.bluez",
                    "org.freedesktop.DBus.Properties",
                    "PropertiesChanged",
                    NULL,
                    "org.bluez.Device1",
                    G_DBUS_SIGNAL_FLAGS_NONE,
                    bluez_signal_device_changed,
                    NULL,
                    NULL);

使用上面的示例代码，只要 Device` 接口中的属性发生变化，就会调用信号处理函数 bluez_signal_device_changed。

您可以在https://gist.github.com/parthitce 中找到更多示例，在https://www.linumiz.com/ 中找到说明