算法：
/**
* 功能：根据rssi计算距离
* Created by liuhuichao on 2017/1/17.
*/
public class RssiUtil {
//A和n的值，需要根据实际环境进行检测得出
private static final double A_Value=50;/**A - 发射端和接收端相隔1米时的信号强度*/
private static final double n_Value=2.5;/** n - 环境衰减因子*/
/**
* 根据Rssi获得返回的距离,返回数据单位为m
* @param rssi
* @return
*/
public static double getDistance(int rssi){
int iRssi = Math.abs(rssi);
double power = (iRssi-A_Value)/(10*n_Value);
return Math.pow(10,power);
}
}
扫描蓝牙过程中获得信号强度：
/*监听扫描过程中的变化*/
private final BroadcastReceiver mReceiver = new BroadcastReceiver() {
@Override
public void onReceive(Context context, Intent intent) {
String action = intent.getAction();
// When discovery finds a device
if (BluetoothDevice.ACTION_FOUND.equals(action))
{
// Get the BluetoothDevice object from the Intent
// 通过EXTRA_DEVICE附加域来得到一个BluetoothDevice设备
BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
// If it's already paired, skip it, because it's been listed already
// 如果这个设备是不曾配对过的，添加到list列表
/* if (device.getBondState() != BluetoothDevice.BOND_BONDED)
{*/
//信号强度
int rssi = intent.getShortExtra(BluetoothDevice.EXTRA_RSSI,Short.MIN_VALUE);
显示时候再根据距离做个排序：
Map map=new HashMap();
map.put("deviceName",deviceName);
map.put("deviceAddress",deviceAddress);
map.put("bluetooth_status",distance);
deviceList.add(map);
Collections.sort(deviceList,new Comparator() {
public int compare(Object a, Object b) {
Map one=(HashMap)a;
Map two=(HashMap)b;
if((((double)one.get("bluetooth_status"))-((double)two.get("bluetooth_status")))>0){
return 1;
}else if((((double)one.get("bluetooth_status"))-((double)two.get("bluetooth_status")))==0){
return 0;
}else{
return -1;
}
}
});
listItemAdapter.notifyDataSetChanged();
