【Android学习】蓝牙扫描

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">
        <TableRow android:layout_height="wrap_content"
            android:layout_width="match_parent">
            <Button
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="刷新列表"
                android:id="@+id/flushBT"></Button>
            <TextView android:layout_height="wrap_content"
                android:layout_width="wrap_content"
                android:id="@+id/sum"
                android:textSize="20dp"
                android:layout_marginLeft="20dp"
                android:text="总计："></TextView>
        </TableRow>
        <ListView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:id="@+id/listshow"></ListView>
    </LinearLayout>

</androidx.constraintlayout.widget.ConstraintLayout>

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.bluetooth">
    <uses-permission android:name="android.permission.BLUETOOTH"></uses-permission>
    <uses-permission android:name="android.permission.BLUETOOTH_ADMIN"></uses-permission>
    <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

MainActivity.java

package com.example.bluetooth;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;

import android.Manifest;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.bluetooth.BluetoothManager;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.content.pm.PackageManager;
import android.os.Build;
import android.os.Bundle;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;

import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity {
    private ListView listView;
    private Button btn;
    private TextView textView;
    private BlueToothReceiver blueToothReceiver;
    private List<String> listdata;
    private ArrayAdapter adapter;
    private BluetoothManager bluetoothManager;
    private BluetoothAdapter bluetoothAdapter;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        listView = findViewById(R.id.listshow);
        btn = findViewById(R.id.flushBT);
        textView = findViewById(R.id.sum);

        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M){
            if (this.checkSelfPermission(Manifest.permission.ACCESS_COARSE_LOCATION)
            != PackageManager.PERMISSION_GRANTED)
            {
                requestPermissions(new String[]{Manifest.permission.ACCESS_COARSE_LOCATION},0x123);
            }else{
                InitBT();
            }
        }


        listdata = new ArrayList<>();
        adapter = new ArrayAdapter(this,android.R.layout.simple_list_item_1,listdata);
        listView.setAdapter(adapter);

        IntentFilter intentFilter = new IntentFilter();
        intentFilter.addAction(BluetoothDevice.ACTION_FOUND);
        intentFilter.addAction(BluetoothAdapter.ACTION_DISCOVERY_STARTED);
        intentFilter.addAction(BluetoothAdapter.ACTION_DISCOVERY_FINISHED);
        blueToothReceiver = new BlueToothReceiver();
        registerReceiver(blueToothReceiver,intentFilter);

        ScanBT();

        btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                ScanBT();
            }
        });
    }
    private void ScanBT(){
        listdata.clear();
        if (bluetoothAdapter.isDiscovering()){
            bluetoothAdapter.cancelDiscovery();
        }
        bluetoothAdapter.startDiscovery();
    }
    private void InitBT(){
        bluetoothManager = (BluetoothManager) getSystemService(BLUETOOTH_SERVICE);
        bluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
        if (bluetoothAdapter == null)
        {
            Toast.makeText(MainActivity.this,"蓝牙不可用",Toast.LENGTH_LONG).show();
            return ;
        }
        if (!bluetoothAdapter.isEnabled())
        {
            Toast.makeText(MainActivity.this,"蓝牙未开启",Toast.LENGTH_LONG).show();
            return ;
        }
    }
    @Override
    protected void onDestroy() {
        unregisterReceiver(blueToothReceiver);
        super.onDestroy();
    }

    public class BlueToothReceiver extends BroadcastReceiver{
        @Override
        public void onReceive(Context context, Intent intent) {
            if (intent.getAction().equals(BluetoothDevice.ACTION_FOUND)){
                BluetoothDevice device = (BluetoothDevice)intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
                short rssi = intent.getExtras().getShort(BluetoothDevice.EXTRA_RSSI);
                for (int i =0;i<listdata.size();i++)
                {
                    if (listdata.get(i).contains(device.getAddress()))
                        return;
                }
                listdata.add(device.getName()+"
"+device.getAddress()+"
"+String.valueOf(rssi));
                adapter.notifyDataSetChanged();
            }
            if (intent.getAction().equals(BluetoothAdapter.ACTION_DISCOVERY_FINISHED)){
                textView.setText("总计："+String.valueOf(listdata.size()));
            }
        }
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        if (requestCode == 0x123){
            InitBT();
        }
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
    }
}

对于我这个初学者来说，整个代码都比较简单，就不解释了

蓝牙强度rssi：

单位是dbm，蓝牙信号的强度RSSI = 10*log P，P代表接收到的信号功率。蓝牙会发送广播，距离大小会影响信号功率强弱。假设发射功率取最大值为1mw，那么RSSI的值为0，也就是说你的距离离蓝牙最近时在理想状态下所获取的RSSI的值为0，但在实际中基本不会存在这个理想状态，因此RSSI的值基本都为负数。

rssi可以用来定位蓝牙设备位置

运行效果如下，小米3 Android6.0；华为Mate10pro Android9.0，Android Studio3.5.0