问题

APK UI上的转圈启、停是根据什么广播来的，安卓原生实际的扫描时间如何控制

分析

扫描开始广播

BluetoothAdapter.ACTION_DISCOVERY_STARTED = "android.bluetooth.adapter.action.DISCOVERY_STARTED";

扫描完成广播

BluetoothAdapter.ACTION_DISCOVERY_FINISHED = "android.bluetooth.adapter.action.DISCOVERY_FINISHED";

如下路径发出广播
packages\apps\Bluetooth\src\com\android\bluetooth\btservice\AdapterProperties.java

    void discoveryStateChangeCallback(int state) {
        infoLog("Callback:discoveryStateChangeCallback with state:" + state);
        synchronized (mObject) {
            Intent intent;
            if (state == AbstractionLayer.BT_DISCOVERY_STOPPED) {
                mDiscovering = false;
                mService.clearDiscoveringPackages();
                mDiscoveryEndMs = System.currentTimeMillis();
                intent = new Intent(BluetoothAdapter.ACTION_DISCOVERY_FINISHED);
                mService.sendBroadcast(intent, AdapterService.BLUETOOTH_PERM);
            } else if (state == AbstractionLayer.BT_DISCOVERY_STARTED) {
                mDiscovering = true;
                mDiscoveryEndMs = System.currentTimeMillis() + DEFAULT_DISCOVERY_TIMEOUT_MS;
                intent = new Intent(BluetoothAdapter.ACTION_DISCOVERY_STARTED);
                mService.sendBroadcast(intent, AdapterService.BLUETOOTH_PERM);
            }
        }
    }

协议栈中实际扫描时间控制

system\bt\btif\src\btif_dm.cc

/*******************************************************************************
 *
 * Function         btif_dm_start_discovery
 *
 * Description      Start device discovery/inquiry
 *
 * Returns          bt_status_t
 *
 ******************************************************************************/
bt_status_t btif_dm_start_discovery(void) {
  tBTA_DM_INQ inq_params;
  tBTA_SERVICE_MASK services = 0;

  BTIF_TRACE_EVENT("%s", __func__);

  /* Cleanup anything remaining on index 0 */
  do_in_main_thread(
      FROM_HERE,
      base::Bind(&BTM_BleAdvFilterParamSetup, BTM_BLE_SCAN_COND_DELETE, 0,
                 nullptr, base::Bind(&bte_scan_filt_param_cfg_evt, 0)));

  auto adv_filt_param = std::make_unique<btgatt_filt_param_setup_t>();
  /* Add an allow-all filter on index 0*/
  adv_filt_param->dely_mode = IMMEDIATE_DELY_MODE;
  adv_filt_param->feat_seln = ALLOW_ALL_FILTER;
  adv_filt_param->filt_logic_type = BTA_DM_BLE_PF_FILT_LOGIC_OR;
  adv_filt_param->list_logic_type = BTA_DM_BLE_PF_LIST_LOGIC_OR;
  adv_filt_param->rssi_low_thres = LOWEST_RSSI_VALUE;
  adv_filt_param->rssi_high_thres = LOWEST_RSSI_VALUE;
  do_in_main_thread(
      FROM_HERE, base::Bind(&BTM_BleAdvFilterParamSetup, BTM_BLE_SCAN_COND_ADD,
                            0, base::Passed(&adv_filt_param),
                            base::Bind(&bte_scan_filt_param_cfg_evt, 0)));

  /* TODO: Do we need to handle multiple inquiries at the same time? */

  /* Set inquiry params and call API */
  inq_params.mode = BTA_DM_GENERAL_INQUIRY | BTA_BLE_GENERAL_INQUIRY;
  inq_params.duration = BTIF_DM_DEFAULT_INQ_MAX_DURATION;

  inq_params.max_resps = BTIF_DM_DEFAULT_INQ_MAX_RESULTS;
  inq_params.report_dup = true;

  inq_params.filter_type = BTA_DM_INQ_CLR;
  /* TODO: Filter device by BDA needs to be implemented here */

  /* Will be enabled to true once inquiry busy level has been received */
  btif_dm_inquiry_in_progress = false;
  /* find nearby devices */
  BTA_DmSearch(&inq_params, services, bte_search_devices_evt);

  return BT_STATUS_SUCCESS;
}

其中 BTIF_DM_DEFAULT_INQ_MAX_DURATION可以控制实际扫描时长，unit--1.28s

Note：packages\apps\Bluetooth\src\com\android\bluetooth\btservice\AdapterProperties.java中的private static final long DEFAULT_DISCOVERY_TIMEOUT_MS = 12800;并不能改变实际扫描时长