关键词：蓝牙blueZ A2DP、SINK、sink_connect、sink_disconnect、sink_suspend、sink_resume、sink_is_connected、sink_get_properties、AUDIO、DBUS
版本：基于android4.2之前版本 bluez
内核：linux/linux3.08
系统：android/android4.1.3.4
作者：xubin341719(欢迎转载，请注明作者，请尊重版权谢谢)
欢迎指正错误，共同学习、共同进步！！
参考网站：
http://blog.csdn.net/u011960402/article/details/17216563
http://www.cnblogs.com/fityme/archive/2013/04/13/3019471.html socket相关
http://hi.baidu.com/wwwkljoel/item/a35e5745d14e02e6bcf45170 setsockopt
一、蓝牙扫描常用的方法：
蓝牙扫描的可以通过两种途径实现：命令行hciitool扫描；Android界面触发，通过JNI、DUBS下发命令。
1、 命令行hciitool扫描（这部分通过Linux命令操作，跟android没有关系）
通过bluez的tool发送扫描命令，如：hcitoool scan
adb shell 下#hcitool scan扫描结果
Hcitool扫描逻辑如下所示：
2、Android界面触发，通过JNI、DUBS下发命令：通过android界面点击搜索设备
应用扫描触发逻辑流程：自上而下三种颜色，分别代表应用部分、JNI部分、linux blueZ部分。二、Hcitool触发逻辑分析
1、hcitool这部分代码比较简单，实现函数
idh.code\external\bluetooth\bluez\tools\hcitool.c代码大致流程如下：
通过所带的参数，找到cmd_scan,进入hci_inquriy。这个函数中创建一个BTPROTO_HCI的socket,通过ioctlHCINQUIRY向内核读取数据，保存返回信息。
2、内核层逻辑：
当然IOCTL只是其中一项。
idh.code\kernel\net\bluetooth\ hci_sock.c
static const struct proto_ops hci_sock_ops = {
…………
.ioctl = hci_sock_ioctl,
.poll = datagram_poll,
.listen = sock_no_listen,
…………
};
它的流程就是构造查询命令，放入命令队列，调度队列来发送命令，其中hci_send_frame后面会讲解，这里关键是命令的发送和数据的收集是分开的，所以它在里面会放弃2s的调度，以此来等待数据的收集，收集的数据放在hdev->inq_cache里面，我们来看看这个数据是如何取得的，如下图所示：
入口点hci_rx_work前面已经详细分析过了，这里就不说了，它里面会根据不同的事件类型做不同的处理，通常情况下，扫描都是带信号强度的扫描，所以走的hci_inquiry_result_with_rssi_evt路线，还有其它几种扫描方式，比如：HCI_EV_INQUIRY_RESULT，HCI_EV_EXTENDED_INQUIRY_RESULT等，处理逻辑都差不多的，里面会hci_inquiry_cache_update来把结果放到hdev->discovery链表里面去，供后面的查询；比如前面调用的inquiry_cache_dump函数就可以从这个链表里面把数据取出来，然后copy到用户层；
三、Android界面触发，通过JNI、DUBS下发命令
整体流程如下所示：
（一）、应用部分：
1、 idh.code\packages\apps\Settings\src\com\android\settings\bluetooth\DeviceListPreferenceFragment.java
@Override
public boolean onPreferenceTreeClick(PreferenceScreen preferenceScreen,
Preference preference) {
…………
mLocalAdapter.startScanning(true);
return true;
}
2、 idh.code\packages\apps\Settings\src\com\android\settings\bluetooth\LocalBluetoothAdapter.java
private final BluetoothAdapter mAdapter;
void startScanning(boolean force) {
// Only start if we‘re not already scanning
if (!mAdapter.isDiscovering()) {
if (!force) {
// Don‘t scan more than frequently than SCAN_EXPIRATION_MS,
// unless forced
if (mLastScan + SCAN_EXPIRATION_MS > System.currentTimeMillis()) {
return;
}
// If we are playing music, don‘t scan unless forced.
A2dpProfile a2dp = mProfileManager.getA2dpProfile();
if (a2dp != null && a2dp.isA2dpPlaying()) {
return;
}
}
if (mAdapter.startDiscovery()) {
mLastScan = System.currentTimeMillis();
}
}
}
3、idh.code\frameworks\base\core\java\android\bluetooth\BluetoothAdapter.java
public boolean startDiscovery() {
if (getState() != STATE_ON) return false;
try {
return mService.startDiscovery();
} catch (RemoteException e) {Log.e(TAG, "", e);}
return false;
}
4、JNI函数的调用idh.code\frameworks\base\core\java\android\server\BluetoothService.java
private native boolean startDiscoveryNative();//Native函数声明
public class BluetoothService extends IBluetooth.Stub {
private static final String TAG = "BluetoothService";
private static final boolean DBG = true;
…………
public synchronized boolean startDiscovery() {
mContext.enforceCallingOrSelfPermission(BLUETOOTH_ADMIN_PERM,
"Need BLUETOOTH_ADMIN permission");
if (!isEnabledInternal()) return false;
return startDiscoveryNative();
}
………………
}
（二）、JNI部分：
1、android_server_BluetoothService.cpp中JNI函数的对照表
idh.code\frameworks\base\core\jni\android_server_BluetoothService.cpp
static JNINativeMethod sMethods[] = {
/* name, signature, funcPtr */
………………
{"startDiscoveryNative", "()Z", (void*)startDiscoveryNative},
{"stopDiscoveryNative", "()Z", (void *)stopDiscoveryNative},
…………
}
2、对应Native函数的实现
这里面有个知识点DBUS，这个后面我们单独去讲解
idh.code\frameworks\base\core\jni\android_server_BluetoothService.cpp
#define BLUEZ_DBUS_BASE_IFC "org.bluez"
#define DBUS_ADAPTER_IFACE BLUEZ_DBUS_BASE_IFC ".Adapter"//其实DBUS_ADAPTER_IFACE 也就是 org.bluez.Adapter
static jboolean startDiscoveryNative(JNIEnv *env, jobject object) {
………………
/* Compose the command */
msg = dbus_message_new_method_call(BLUEZ_DBUS_BASE_IFC,
get_adapter_path(env, object),
DBUS_ADAPTER_IFACE, "StartDiscovery");
…………
}
Native函数startDiscoveryNative和字符串StartDiscovery对应。
（三）、DBUS部分
1、DBUS对应方法的实现，这里跟JNI部分比较类似，也是用了函数结构体对应关系。
idh.code\external\bluetooth\bluez\src\adapter.c
#define ADAPTER_INTERFACE "org.bluez.Adapter"
static GDBusMethodTable adapter_methods[] = {
………………
{ "ReleaseSession", "", "", release_session },
{ "StartDiscovery", "", "", adapter_start_discovery },
{ "StopDiscovery", "", "", adapter_stop_discovery,
G_DBUS_METHOD_FLAG_ASYNC},
………………
}
字符StartDiscovery又对应C中的实现函数adapter_start_discovery。
2、adapter_start_discovery的实现
idh.code\external\bluetooth\bluez\src\adapter.c
static DBusMessage *adapter_start_discovery(DBusConnection *conn,
DBusMessage *msg, void *data)
{
…………
err = start_discovery(adapter);
if (err < 0 && err != -EINPROGRESS)
return btd_error_failed(msg, strerror(-err));
done:
req = create_session(adapter, conn, msg, 0,
session_owner_exit);
adapter->disc_sessions = g_slist_append(adapter->disc_sessions, req);
return dbus_message_new_method_return(msg);
}
3、 start_discovery调用
idh.code\external\bluetooth\bluez\src\adapter.c
const struct btd_adapter_ops *adapter_ops = NULL;
static int start_discovery(struct btd_adapter *adapter)
{
…………
pending_remote_name_cancel(adapter);
return adapter_ops->start_discovery(adapter->dev_id);
}
adapter_ops对应结构体btd_adapter_ops中对应函数，如下：上面部分就对应到btd_adapter_ops中的hci_ops结构体。
4、btd_adapter_ops中的hci_ops结构体
idh.code\external\bluetooth\bluez\plugins\hciops.c
static struct btd_adapter_ops hci_ops = {
…………
.set_powered = hciops_set_powered,
.set_discoverable = hciops_set_discoverable,
.set_pairable = hciops_set_pairable,
.set_limited_discoverable = hciops_set_limited_discoverable,
.start_discovery = hciops_start_discovery,
.stop_discovery = hciops_stop_discovery,
………………
.create_bonding = hciops_create_bonding,
.cancel_bonding = hciops_cancel_bonding,
.read_local_oob_data = hciops_read_local_oob_data,
.add_remote_oob_data = hciops_add_remote_oob_data,
.remove_remote_oob_data = hciops_remove_remote_oob_data,
.set_link_timeout = hciops_set_link_timeout,
.retry_authentication = hciops_retry_authentication,
};
5、hciops_start_discovery函数的实现
idh.code\external\bluetooth\bluez\plugins\hciops.c
static int hciops_start_discovery(int index)
{
int adapter_type = get_adapter_type(index);
switch (adapter_type) {
case BR_EDR_LE:
return hciops_start_inquiry(index, LENGTH_BR_LE_INQ);
case BR_EDR: //蓝牙芯片为2.1+EDR的
return hciops_start_inquiry(index, LENGTH_BR_INQ);
case LE_ONLY:
return hciops_start_scanning(index, TIMEOUT_LE_SCAN);
default:
return -EINVAL;
}
}
6、hciops_start_inquiry
idh.code\external\bluetooth\bluez\plugins\hciops.c
static int hciops_start_inquiry(int index, uint8_t length)
{
struct dev_info *dev = &devs[index];
uint8_t lap[3] = { 0x33, 0x8b, 0x9e };
inquiry_cp inq_cp;
DBG("hci%d length %u", index, length);
memset(&inq_cp, 0, sizeof(inq_cp));
memcpy(&inq_cp.lap, lap, 3);
inq_cp.length = length;
inq_cp.num_rsp = 0x00;
if (hci_send_cmd(dev->sk, OGF_LINK_CTL,
OCF_INQUIRY, INQUIRY_CP_SIZE, &inq_cp) < 0)
return -errno;
return 0;
}
7、idh.code\external\bluetooth\bluez\lib\hci.c
/* HCI functions that require open device
* dd - Device descriptor returned by hci_open_dev. */
dd = socket(AF_BLUETOOTH, SOCK_RAW, BTPROTO_HCI);
int hci_send_cmd(int dd, uint16_t ogf, uint16_t ocf, uint8_t plen, void *param)
{
………………
if (plen) {
iv[2].iov_base = param;
iv[2].iov_len = plen;
ivn = 3;
}
while (writev(dd, iv, ivn) < 0) {//writev这里把数据写到socket里面。
if (errno == EAGAIN || errno == EINTR)
continue;
return -1;
}
return 0;
}
（四）、内核部分：
1、HCI FILTER的设置
HCIsocket的类型为BTPROTO_HCI。上层调用setsockopt的时候，触发了内核的hci_sock_setsockopt函数的执行，在这里面设置了socket的filter特性，包括包类型，包括事件类型；
当上层调用setsockopt(sock, SOL_HCI, HCI_FILTER,&flt, sizeof(flt))时，触发相应的内核路径。
idh.code\kernel\net\bluetooth\hci_sock.c
static const struct proto_ops hci_sock_ops = {
.family = PF_BLUETOOTH,
.owner = THIS_MODULE,
…………
.shutdown = sock_no_shutdown,
.setsockopt = hci_sock_setsockopt,
.getsockopt = hci_sock_getsockopt,
.connect = sock_no_connect,
…………
};
idh.code\kernel\net\bluetooth\hci_sock.c
static int hci_sock_setsockopt(struct socket *sock, int level, int optname, char __user *optval, unsigned int len)
{
………………
case HCI_FILTER:
{
struct hci_filter *f = &hci_pi(sk)->filter;
uf.type_mask = f->type_mask;
uf.opcode = f->opcode;
uf.event_mask[0] = *((u32 *) f->event_mask + 0);
uf.event_mask[1] = *((u32 *) f->event_mask + 1);
}
………………
}
内核这部分就比较统一的数据，通过hci_send_cmd把命令发出去，HCI_FILTER这个地方的处理还没理解，后面补充。
Writev函数通过socket把数据写下去，经过VFS层，调用到内核空间的sendmsg函数。
（五）、EVENT返回状态
Controller收到查询命令后，返回一个命令状态
1、cmd_status
idh.code\external\bluetooth\bluez\plugins\hciops.c
switch (eh->evt) {
case EVT_CMD_STATUS:
cmd_status(index, ptr);
break;
static inline void cmd_status(int index, void *ptr)
{
evt_cmd_status *evt = ptr;
uint16_t opcode = btohs(evt->opcode);
if (opcode == cmd_opcode_pack(OGF_LINK_CTL, OCF_INQUIRY))//如果是inquriy做特殊处理；
cs_inquiry_evt(index, evt->status);
}
2、cs_inquiry_evt的实现 idh.code\external\bluetooth\bluez\plugins\hciops.c
static inline void cs_inquiry_evt(int index, uint8_t status)
{
if (status) {//错误信息
error("Inquiry Failed with status 0x%02x", status);
return;
}
set_state(index, DISCOV_INQ);//设置状态为INQ，向上层回复discoverying的property change
}
3、设置不同的DISCOV 状态 idh.code\external\bluetooth\bluez\plugins\hciops.c
static void set_state(int index, int state)
{
………………
switch (dev->discov_state) {
case DISCOV_HALTED://停止发现;
if (adapter_get_state(adapter) == STATE_SUSPENDED)
return;
if (is_resolvname_enabled() &&
adapter_has_discov_sessions(adapter))
adapter_set_state(adapter, STATE_RESOLVNAME);
else
adapter_set_state(adapter, STATE_IDLE);
break;
case DISCOV_INQ:
case DISCOV_SCAN://扫描发现；
adapter_set_state(adapter, STATE_DISCOV);
break;
}
}
4、设置adapter的状态 idh.code\external\bluetooth\bluez\src\adapter.c
idh.code\external\bluetooth\bluez\src\adapter.c
#define ADAPTER_INTERFACE "org.bluez.Adapter"
void adapter_set_state(struct btd_adapter *adapter, int state)
{
…………
case STATE_DISCOV:
discov_active = TRUE;
//向上层回复discovering的property change
emit_property_changed(connection, path,
ADAPTER_INTERFACE, "Discovering",
DBUS_TYPE_BOOLEAN, &discov_active);
break;
…………
}
emit_property_changed发送PropertyChanged的消息，消息内容为Discovering。通知上层BluetoothEventLoop进行Discovering。
5、emit_property_changed发送Discovering消息的实现 idh.code\external\bluetooth\bluez\src\dbus-common.c
这部分涉及到DBUS内容
dbus_bool_t emit_property_changed(DBusConnection *conn,
const char *path,
const char *interface,
const char *name,
int type, void *value)
{
DBusMessage *signal;
DBusMessageIter iter;
signal = dbus_message_new_signal(path, interface, "PropertyChanged"); // 创建消息对象并标识路径
if (!signal) {
error("Unable to allocate new %s.PropertyChanged signal",
interface);
return FALSE;
}
dbus_message_iter_init_append(signal, &iter);//把信号相对应的参数压进去
dbus_message_iter_append_basic(&iter, DBUS_TYPE_STRING, &name);//申请一个首地址，把前面压入的参数传入这个首地址
append_variant(&iter, type, value);//
return g_dbus_send_message(conn, signal);//启动发送调用，并释放发送相关消息信息
}
6、DBUS消息接收的实现 idh.code\frameworks\base\core\jni\android_server_BluetoothEventLoop.cpp
// Called by dbus during WaitForAndDispatchEventNative()
static DBusHandlerResult event_filter(DBusConnection *conn, DBusMessage *msg,
void *data) {
…………
else if (dbus_message_is_signal(msg, "org.bluez.Adapter", "PropertyChanged")) {
jobjectArray str_array = parse_adapter_property_change(env, msg);//（1）、对收到消息的解析
if (str_array != NULL) {
/* Check if bluetoothd has (re)started, if so update the path. */
jstring property =(jstring) env->GetObjectArrayElement(str_array, 0);
const char *c_property = env->GetStringUTFChars(property, NULL);
if (!strncmp(c_property, "Powered", strlen("Powered"))) {
jstring value =
(jstring) env->GetObjectArrayElement(str_array, 1);
const char *c_value = env->GetStringUTFChars(value, NULL);
if (!strncmp(c_value, "true", strlen("true")))
nat->adapter = get_adapter_path(nat->conn);
env->ReleaseStringUTFChars(value, c_value);
}
env->ReleaseStringUTFChars(property, c_property);
env->CallVoidMethod(nat->me,
method_onPropertyChanged,//（2）、
method_onPropertyChanged NATVIE函数的实现
str_array);
} else LOG_AND_FREE_DBUS_ERROR_WITH_MSG(&err, msg);
goto success;
}
（1）、对收到消息的解析 idh.code\frameworks\base\core\jni\android_bluetooth_common.cpp
jobjectArray parse_adapter_property_change(JNIEnv *env, DBusMessage *msg) {
return parse_property_change(env, msg, (Properties *) &adapter_properties,
sizeof(adapter_properties) / sizeof(Properties));
}
针对org.bluez.Adapter不同的消息类型
idh.code\frameworks\base\core\jni\android_bluetooth_common.cpp
static Properties adapter_properties[] = {
{"Address", DBUS_TYPE_STRING},
{"Name", DBUS_TYPE_STRING},
{"Class", DBUS_TYPE_UINT32},
{"Powered", DBUS_TYPE_BOOLEAN},
{"Discoverable", DBUS_TYPE_BOOLEAN},
{"DiscoverableTimeout", DBUS_TYPE_UINT32},
{"Pairable", DBUS_TYPE_BOOLEAN},
{"PairableTimeout", DBUS_TYPE_UINT32},
{"Discovering", DBUS_TYPE_BOOLEAN},
{"Devices", DBUS_TYPE_ARRAY},
{"UUIDs", DBUS_TYPE_ARRAY},
};
（2）、method_onPropertyChanged NATVIE函数的实现 idh.code\frameworks\base\core\jni\android_server_BluetoothEventLoop.cpp
static void classInitNative(JNIEnv* env, jclass clazz) {
ALOGV("%s", __FUNCTION__);
#ifdef HAVE_BLUETOOTH
method_onPropertyChanged = env->GetMethodID(clazz, "onPropertyChanged",
"([Ljava/lang/String;)V");
method_onDevicePropertyChanged = env->GetMethodID(clazz,
"onDevicePropertyChanged","(Ljava/lang/String;[Ljava/lang/String;)V");
…………
}
7、JNI调用onPropertyChanged对应JAVA的实现，在BluetoothEventLoop.java
idh.code\frameworks\base\core\java\android\server\BluetoothEventLoop.java中
private static native void classInitNative();
/*package*/ void onPropertyChanged(String[] propValues) {
………………
log("Property Changed: " + propValues[0] + " : " + propValues[1]);
String name = propValues[0];
if (name.equals("Name")) {//获取蓝牙名字；
…………
} else if (name.equals("Pairable") || name.equals("Discoverable")) {//配对；
………………
} else if (name.equals("Discovering")) {//扫描查询；
Intent intent;
adapterProperties.setProperty(name, propValues[1]);
if (propValues[1].equals("true")) {
intent = new Intent(BluetoothAdapter.ACTION_DISCOVERY_STARTED);
} else {
// Stop the discovery.
mBluetoothService.cancelDiscovery();
intent = new Intent(BluetoothAdapter.ACTION_DISCOVERY_FINISHED);
}
mContext.sendBroadcast(intent, BLUETOOTH_PERM);
} else if (name.equals("Devices") || name.equals("UUIDs")) {//Devices、UUID的获取；
………………
} else if (name.equals("Powered")) {//蓝牙打开、关闭；
mBluetoothState.sendMessage(BluetoothAdapterStateMachine.POWER_STATE_CHANGED,
propValues[1].equals("true") ? new Boolean(true) : new Boolean(false));
} else if (name.equals("DiscoverableTimeout")) {
adapterProperties.setProperty(name, propValues[1]);
}
} D BluetoothEventLoop: Property Changed: Powered : true D BluetoothEventLoop: Property Changed: Pairable : true D BluetoothEventLoop: Property Changed: Class : 5898764 D BluetoothEventLoop: Property Changed: Pairable : true D BluetoothEventLoop: Property Changed: Discoverable : false D BluetoothEventLoop: Property Changed: Discovering : true D BluetoothEventLoop: Property Changed: Discovering : false D BluetoothEventLoop: Property Changed: Devices : 1 D BluetoothEventLoop: Device property changed: 94:20:53:01:15:90 property: Connected value: true D BluetoothEventLoop: Device property changed: 94:20:53:01:15:90 property: Paired value: true D BluetoothEventLoop: Device property changed: 94:20:53:01:15:90 property: UUIDs value: 4
（2）、下面我们重点分析Discovering这部分：
idh.code\frameworks\base\core\java\android\server\BluetoothEventLoop.java
else if (name.equals("Discovering")) {
Intent intent;
adapterProperties.setProperty(name, propValues[1]);
if (propValues[1].equals("true")) {//开始扫描
intent = new Intent(BluetoothAdapter.ACTION_DISCOVERY_STARTED);//
} else {
// Stop the discovery. //停止扫描
mBluetoothService.cancelDiscovery();
intent = new Intent(BluetoothAdapter.ACTION_DISCOVERY_FINISHED);
}
mContext.sendBroadcast(intent, BLUETOOTH_PERM);
}
这样就可以通过broadcast发送ACTION_DISCOVERY_STARTED广播，注册的receiver来响应了。
8、ACTION_DISCOVERY_STARTED\ACTION_DISCOVERY_FINISHED的receiver分析
从代码中我们可以看到这个action一共有两个receiver，一个是静态注册的BluetoothDiscoveryReceiver,一个是动态注册是ScanningStateChangedHandler。
（1）、BluetoothDiscoveryReceiver：这个receiver是在settings中的Androidmanifest中静态注册的。用途：主要用于获取扫描开始和终止的时间。
idh.code\packages\apps\Settings\AndroidManifest.xml
<receiver
android:name=".bluetooth.BluetoothDiscoveryReceiver">
<intent-filter>
<action android:name="android.bluetooth.adapter.action.DISCOVERY_STARTED" />
<action android:name="android.bluetooth.adapter.action.DISCOVERY_FINISHED" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</receiver>
1）、ACTION_DISCOVERY_STARTED、ACTION_DISCOVERY_FINISHED和AndroidManifest.xml文件的联系
idh.code\frameworks\base\core\java\android\bluetooth\BluetoothAdapter.java
public final class BluetoothAdapter {
private static final String TAG = "BluetoothAdapter";
private static final boolean DBG = false;
…………
public static final String ACTION_DISCOVERY_STARTED =
"android.bluetooth.adapter.action.DISCOVERY_STARTED";
public static final String ACTION_DISCOVERY_FINISHED =
"android.bluetooth.adapter.action.DISCOVERY_FINISHED";
…………
}
2）、BluetoothAdapter，蓝牙适配器，直到我们建立bluetoothSocket连接之前，都要不断操作它。
BluetoothAdapter中的动作常量
ACTION_DISCOVERY_FINISHED | 已完成蓝牙搜索 |
ACTION_DISCOVERY_STARTED | 已经开始搜索蓝牙设备 |
ACTION_LOCAL_NAME_CHANGED | 更改蓝牙的名字 |
ACTION_REQUEST_DISCOVERABLE | 请求能够被搜索 |
ACTION_REQUEST_ENABLE | 请求启动蓝牙 |
ACTION_SCAN_MODE_CHANGED | 扫描模式已经改变 |
ACTION_STATE_CHANGED | 状态已改变 |
ACTION_CONNECTION_STATE_CHANGED |
|
3）、收到广播后函数实现，开始扫描
Main log中显示的log为DISCOVERY_STARTED
D BluetoothDiscoveryReceiver: Received:android.bluetooth.adapter.action.DISCOVERY_STARTED
HCI log 中：
idh.code\packages\apps\Settings\src\com\android\settings\bluetooth\BluetoothDiscoveryReceiver.java这个文件中就一个函数，还是比简单
public final class BluetoothDiscoveryReceiver extends BroadcastReceiver {
private static final String TAG = "BluetoothDiscoveryReceiver";
private static final boolean DEBUG = Debug.isDebug();
@Override
public void onReceive(Context context, Intent intent) {
String action = intent.getAction();
if (DEBUG) Log.d(TAG, "Received: " + action);
if (action.equals(BluetoothAdapter.ACTION_DISCOVERY_STARTED) ||
action.equals(BluetoothAdapter.ACTION_DISCOVERY_FINISHED)) {
//共享时间戳，扫描开始和结束的时间。
LocalBluetoothPreferences.persistDiscoveringTimestamp(context);
}
}
}
ScanningStateChangedHandler的注册及用途，要用于开始扫描，和扫描显示界面的控制。
这个receiver是在idh.code\packages\apps\Settings\src\com\android\settings\bluetooth\BluetoothEventManager.java动态注册的，如下：
BluetoothEventManager(LocalBluetoothAdapter adapter,
CachedBluetoothDeviceManager deviceManager, Context context) {
mLocalAdapter = adapter;
…………
// Bluetooth on/off broadcasts
addHandler(BluetoothAdapter.ACTION_STATE_CHANGED, new AdapterStateChangedHandler());
// Discovery broadcastsaddHandler(BluetoothAdapter.ACTION_DISCOVERY_STARTED, new ScanningStateChangedHandler(true));
addHandler(BluetoothAdapter.ACTION_DISCOVERY_FINISHED, new ScanningStateChangedHandler(false));
…………
}
（1）、ScanningStateChangedHandler函数实现如下：idh.code\packages\apps\Settings\src\com\android\settings\bluetooth\BluetoothEventManager.java
private class ScanningStateChangedHandler implements Handler {
private final boolean mStarted;
ScanningStateChangedHandler(boolean started) {
mStarted = started;
}
public void onReceive(Context context, Intent intent,
BluetoothDevice device) {
synchronized (mCallbacks) {//1)、调用注册的callback
中的onScanningStateChanged函数。
for (BluetoothCallback callback : mCallbacks) {
callback.onScanningStateChanged(mStarted);
}
}
//2）、这个函数就是把上次扫描到设备、和之前的设备做相应处理；
mDeviceManager.onScanningStateChanged(mStarted);
LocalBluetoothPreferences.persistDiscoveringTimestamp(context);
}
}
1）、调用注册的callback中的callback.onScanningStateChanged(mStarted)函数。
idh.code\packages\apps\Settings\src\com\android\settings\bluetooth\DeviceListPreferenceFragment.java
public void onScanningStateChanged(boolean started) {
if (started == false) {//《1》、如果扫描结束；
removeOutOfRangeDevices();
}
updateProgressUi(started);// 《2》、UI显示小圆圈扫描；
}
《1》、如果扫描结束；removeOutOfRangeDevices();
idh.code\packages\apps\Settings\src\com\android\settings\bluetooth\DeviceListPreferenceFragment.java
private void removeOutOfRangeDevices() {
Collection<CachedBluetoothDevice> cachedDevices =
mLocalManager.getCachedDeviceManager().getCachedDevicesCopy();
for (CachedBluetoothDevice cachedDevice : cachedDevices) {
if (cachedDevice.getBondState() == BluetoothDevice.BOND_NONE &&
cachedDevice.isVisible() == false) {
BluetoothDevicePreference preference = mDevicePreferenceMap.get(cachedDevice);
if (preference != null) {
mDeviceListGroup.removePreference(preference);
}
mDevicePreferenceMap.remove(cachedDevice);
}
}
}
《2》、UI显示小圆圈扫描，updateProgressUi(started)；如下图所示：
idh.code\packages\apps\Settings\src\com\android\settings\bluetooth\DeviceListPreferenceFragment.java
private void updateProgressUi(boolean start) {
if (mDeviceListGroup instanceof ProgressCategory) {
((ProgressCategory) mDeviceListGroup).setProgress(start);
}
}
2）、这部分的作用，开始扫描，不显示列表中内容，或把之前列表中没扫描到的设备清除
mDeviceManager.onScanningStateChanged(mStarted);
idh.code\packages\apps\Settings\src\com\android\settings\bluetooth\CachedBluetoothDevice.java
private void updateProgressUi(boolean start) {
if (mDeviceListGroup instanceof ProgressCategory) {
((ProgressCategory) mDeviceListGroup).setProgress(start);
}
}
2）、这部分的作用，开始扫描，不显示列表中内容，或把之前列表中没扫描到的设备清除
mDeviceManager.onScanningStateChanged(mStarted);
idh.code\packages\apps\Settings\src\com\android\settings\bluetooth\ CachedBluetoothDevice.java
public synchronized void onScanningStateChanged(boolean started) {
// If starting a new scan, clear old visibility
// Iterate in reverse order since devices may be removed.
//如果开始新的扫描，清除旧的能见设备，迭代反序因为有的设备可能被删除
for (int i = mCachedDevices.size() - 1; i >= 0; i--) {
CachedBluetoothDevice cachedDevice = mCachedDevices.get(i);
if (started) {//如果扫描开始就不显示；
cachedDevice.setVisible(false);
} else {//对扫描的结果作出判断，如果之前扫描过，这次没有扫描到，就移除列表。
if (cachedDevice.getBondState() == BluetoothDevice.BOND_NONE &&
cachedDevice.isVisible() == false) {
mCachedDevices.remove(cachedDevice);
}
}
}
}