Android——蓝牙利用RSSI进行距离测算

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();