您不应该org.freedesktop.DBus.ObjectManager.GetManagedObjects每次都使用来获取对象路径。这GetManagedObjects意味着在您的应用程序启动时获取现有或以前可用的接口及其详细信息。
例如，假设 Bluez 已启动并连接了 1 个终端设备。稍后您的应用程序启动，在您的应用程序的初始化/启动期间，您可能需要获取所有可用/连接的设备，以便您可以使用GetManagedObjects它来获取它。
为了在运行时创建接口、对象路径，您应该依赖信号InterfacesAdded和对象InterfacesRemoved管理器。
我在 python 中没有示例，但以下 C 中的示例通常StartDiscovery使用信号来监视新设备。因此，您可以使用信号来适应 python 中的类似示例。下面的例子只是为了清楚起见（关于这个例子的更多细节在Linumiz中）。
/*
* bluez_adapter_scan.c - Scan for bluetooth devices
* - This example scans for new devices after powering the adapter, if any devices
* appeared in /org/hciX/dev_XX_YY_ZZ_AA_BB_CC, it is monitered using "InterfaceAdded"
* signal and all the properties of the device is printed
* - Scanning continues to run until any device is disappered, this happens after 180 seconds
* automatically if the device is not used.
* gcc `pkg-config --cflags glib-2.0 gio-2.0` -Wall -Wextra -o ./bin/bluez_adapter_scan ./bluez_adapter_scan.c `pkg-config --libs glib-2.0 gio-2.0`
*/
#include <glib.h>
#include <gio/gio.h>
GDBusConnection *con;
static void bluez_property_value(const gchar *key, GVariant *value)
{
const gchar *type = g_variant_get_type_string(value);
g_print("\t%s : ", key);
switch(*type) {
case 'o':
case 's':
g_print("%s\n", g_variant_get_string(value, NULL));
break;
case 'b':
g_print("%d\n", g_variant_get_boolean(value));
break;
case 'u':
g_print("%d\n", g_variant_get_uint32(value));
break;
case 'a':
/* TODO Handling only 'as', but not array of dicts */
if(g_strcmp0(type, "as"))
break;
g_print("\n");
const gchar *uuid;
GVariantIter i;
g_variant_iter_init(&i, value);
while(g_variant_iter_next(&i, "s", &uuid))
g_print("\t\t%s\n", uuid);
break;
default:
g_print("Other\n");
break;
}
}
static void bluez_device_appeared(GDBusConnection *sig,
const gchar *sender_name,
const gchar *object_path,
const gchar *interface,
const gchar *signal_name,
GVariant *parameters,
gpointer user_data)
{
(void)sig;
(void)sender_name;
(void)object_path;
(void)interface;
(void)signal_name;
(void)user_data;
GVariantIter *interfaces;
const char *object;
const gchar *interface_name;
GVariant *properties;
g_variant_get(parameters, "(&oa{sa{sv}})", &object, &interfaces);
while(g_variant_iter_next(interfaces, "{&s@a{sv}}", &interface_name, &properties)) {
if(g_strstr_len(g_ascii_strdown(interface_name, -1), -1, "device")) {
g_print("[ %s ]\n", object);
const gchar *property_name;
GVariantIter i;
GVariant *prop_val;
g_variant_iter_init(&i, properties);
while(g_variant_iter_next(&i, "{&sv}", &property_name, &prop_val))
bluez_property_value(property_name, prop_val);
g_variant_unref(prop_val);
}
g_variant_unref(properties);
}
return;
}
#define BT_ADDRESS_STRING_SIZE 18
static void bluez_device_disappeared(GDBusConnection *sig,
const gchar *sender_name,
const gchar *object_path,
const gchar *interface,
const gchar *signal_name,
GVariant *parameters,
gpointer user_data)
{
(void)sig;
(void)sender_name;
(void)object_path;
(void)interface;
(void)signal_name;
GVariantIter *interfaces;
const char *object;
const gchar *interface_name;
char address[BT_ADDRESS_STRING_SIZE] = {'\0'};
g_variant_get(parameters, "(&oas)", &object, &interfaces);
while(g_variant_iter_next(interfaces, "s", &interface_name)) {
if(g_strstr_len(g_ascii_strdown(interface_name, -1), -1, "device")) {
int i;
char *tmp = g_strstr_len(object, -1, "dev_") + 4;
for(i = 0; *tmp != '\0'; i++, tmp++) {
if(*tmp == '_') {
address[i] = ':';
continue;
}
address[i] = *tmp;
}
g_print("\nDevice %s removed\n", address);
g_main_loop_quit((GMainLoop *)user_data);
}
}
return;
}
static void bluez_signal_adapter_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(g_strcmp0(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, "Powered")) {
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("Adapter is Powered \"%s\"\n", g_variant_get_boolean(value) ? "on" : "off");
}
if(!g_strcmp0(key, "Discovering")) {
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("Adapter scan \"%s\"\n", g_variant_get_boolean(value) ? "on" : "off");
}
}
done:
if(properties != NULL)
g_variant_iter_free(properties);
if(value != NULL)
g_variant_unref(value);
}
static int bluez_adapter_call_method(const char *method)
{
GVariant *result;
GError *error = NULL;
result = g_dbus_connection_call_sync(con,
"org.bluez",
/* TODO Find the adapter path runtime */
"/org/bluez/hci0",
"org.bluez.Adapter1",
method,
NULL,
NULL,
G_DBUS_CALL_FLAGS_NONE,
-1,
NULL,
&error);
if(error != NULL)
return 1;
g_variant_unref(result);
return 0;
}
static int bluez_adapter_set_property(const char *prop, GVariant *value)
{
GVariant *result;
GError *error = NULL;
result = g_dbus_connection_call_sync(con,
"org.bluez",
"/org/bluez/hci0",
"org.freedesktop.DBus.Properties",
"Set",
g_variant_new("(ssv)", "org.bluez.Adapter1", prop, value),
NULL,
G_DBUS_CALL_FLAGS_NONE,
-1,
NULL,
&error);
if(error != NULL)
return 1;
g_variant_unref(result);
return 0;
}
int main(void)
{
GMainLoop *loop;
int rc;
guint prop_changed;
guint iface_added;
guint iface_removed;
con = g_bus_get_sync(G_BUS_TYPE_SYSTEM, NULL, NULL);
if(con == NULL) {
g_print("Not able to get connection to system bus\n");
return 1;
}
loop = g_main_loop_new(NULL, FALSE);
prop_changed = g_dbus_connection_signal_subscribe(con,
"org.bluez",
"org.freedesktop.DBus.Properties",
"PropertiesChanged",
NULL,
"org.bluez.Adapter1",
G_DBUS_SIGNAL_FLAGS_NONE,
bluez_signal_adapter_changed,
NULL,
NULL);
iface_added = g_dbus_connection_signal_subscribe(con,
"org.bluez",
"org.freedesktop.DBus.ObjectManager",
"InterfacesAdded",
NULL,
NULL,
G_DBUS_SIGNAL_FLAGS_NONE,
bluez_device_appeared,
loop,
NULL);
iface_removed = g_dbus_connection_signal_subscribe(con,
"org.bluez",
"org.freedesktop.DBus.ObjectManager",
"InterfacesRemoved",
NULL,
NULL,
G_DBUS_SIGNAL_FLAGS_NONE,
bluez_device_disappeared,
loop,
NULL);
rc = bluez_adapter_set_property("Powered", g_variant_new("b", TRUE));
if(rc) {
g_print("Not able to enable the adapter\n");
goto fail;
}
rc = bluez_adapter_call_method("StartDiscovery");
if(rc) {
g_print("Not able to scan for new devices\n");
goto fail;
}
g_main_loop_run(loop);
rc = bluez_adapter_call_method("StopDiscovery");
if(rc)
g_print("Not able to stop scanning\n");
g_usleep(100);
rc = bluez_adapter_set_property("Powered", g_variant_new("b", FALSE));
if(rc)
g_print("Not able to disable the adapter\n");
fail:
g_dbus_connection_signal_unsubscribe(con, prop_changed);
g_dbus_connection_signal_unsubscribe(con, iface_added);
g_dbus_connection_signal_unsubscribe(con, iface_removed);
g_object_unref(con);
return 0;
}
在这个扫描设备的例子中，StartDiscovery我使用了信号InterfaceRemoved和InterfaceAdded演示。因此，当新设备出现在/org/hciX/,bluez_device_appeared被调用并以相同的方式进行删除时。
如果您连接了多个蓝牙适配器，则可以g_dbus_connection_signal_subscribe通过指定适配器路径来过滤它们，例如/org/bluez/hciX.
所有基于 DBUS 的守护进程都使用信号来通知总线上的客户端，因此我们在总线上看到很多消息。所以我们需要根据确切的需要订阅。此过滤器应用于 dbus 守护程序级别并转发消息。
添加MediaControl1bluez 的接口已过时且不推荐使用。所有新应用程序都应按照此处MediaPlayer定义的方式使用。