android扫描蓝牙信号的小结，startLeScan（）方法和startDiscovery()方法

注意的问题
1：添加权限

<uses-permission android:name="android.permission.BLUETOOTH_ADMIN" />
<uses-permission android:name="android.permission.BLUETOOTH" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />

2：添加运行时权限（SDK23以上一定要加，我就是没加怎么都搞不出来，弄了半天，嘤嘤嘤）

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M &&

        checkSelfPermission(Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED &&

        checkSelfPermission(Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED &&

        checkSelfPermission(Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED ) {

    requestPermissions(new String[]{Manifest.permission.ACCESS_COARSE_LOCATION, Manifest.permission.ACCESS_FINE_LOCATION ,

            Manifest.permission.CAMERA,}, 1);
}

**

小结

：**
首先添加手机中已经配对好的蓝牙设备到 mBluetoothAdapter（也可以不用创建BluetoothAdapter对象即可）。

BluetoothAdapter mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();

方式1，startLeScan（）方法

startLeScan（）方法有一个回调参数BluetoothAdapter.LeScanCallback 类，先创建这个类的对象，在扫描找到周围的蓝牙设备时，会返回到 onLeScan 函数，可以在 onLeScan 函数中处理逻辑

BluetoothAdapter.LeScanCallback mLeScanCallback = new BluetoothAdapter.LeScanCallback() {
      @Override
      public void onLeScan(final BluetoothDevice device, int rssi, byte[] scanRecord) {
          mArrayAdapter.add(device.getName() + "\n" + device.getAddress());
          lv_bluetooth.setAdapter(mArrayAdapter);
          Log.d(TAG, "onLeScan:563463 ");
      }
  };

然后再用 startLeScan（）方法扫描

mBluetoothAdapter.startLeScan(mLeScanCallback);

startLeScan（）方法的特点：在onLeScan() 中不能做耗时操作，特别是周围的BLE设备多的时候，容易导致底层堵塞

方式2，startDiscovery()方法

这个方法用到广播。

所以先定义一个类SingBroadcastReceiver，让他继承自BroadcastReceiver ,并重写onReceive()方法，在该方法中写扫描到设备时的逻辑。

class SingBroadcastReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        String action = intent.getAction();
        if (BluetoothDevice.ACTION_FOUND.equals(action) ){
            // Get the BluetoothDevice object from the Intent
            BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
            // Add the name and address to an array adapter to show in a Toast
            String derp = device.getName() + " - " + device.getAddress();
            Toast.makeText(context, derp, Toast.LENGTH_LONG).show();
        }
    }
}

然后创建SingBroadcastReceiver对象，注册广播，再执行startDiscovery()方法

SingBroadcastReceiver mReceiver=new SingBroadcastReceiver ();
 mBluetoothAdapter.startDiscovery();
 IntentFilter ifilter1= new IntentFilter(BluetoothDevice.ACTION_FOUND);
  registerReceiver(mReceiver, ifilter1);

对于经典蓝牙设备，扫描是通过调用startDiscovery接口，返回的结果是通过BroadcastReceiver接收的，可以获取设备MAC地址，名称以及RSSI。startDiscovery是个异步调用，会立即返回。如果不调用cancelDiscovery主动停止扫描的话，最多扫描12s。广播主要监听以下几个Action：BluetoothDevice.ACTION_FOUNDBluetoothAdapter.ACTION_DISCOVERY_STARTEDBluetoothAdapter.ACTION_DISCOVERY_FINISHED另外要注意startDiscovery返回的设备不包括已配对设备，如要获取已配对设备，需要额外调用getBondedDevices。

例子

我比较喜欢用startDiscovery()，所以是用这个startDiscovery()写的。

public class MainActivity extends AppCompatActivity {
    private ListView lv_bluetooth;//用于显示蓝牙设备
    private SingBroadcastReceiver mReceiver;//这个我自定义的一个广播接收器
    private  ArrayAdapter<String> mArrayAdapter;//一个简单的适配器
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //实例化
        lv_bluetooth=findViewById(R.id.lv_bluetooth);
        Button button_find=findViewById(R.id.find);
        Button button_cancel=findViewById(R.id.cancel);
        mArrayAdapter=new ArrayAdapter<String >(
                MainActivity.this,android.R.layout.simple_list_item_1
        );
        //运行时权限
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M &&

                checkSelfPermission(Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED &&

                checkSelfPermission(Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED &&

                checkSelfPermission(Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED ) {

            requestPermissions(new String[]{Manifest.permission.ACCESS_COARSE_LOCATION, Manifest.permission.ACCESS_FINE_LOCATION ,

                    Manifest.permission.CAMERA,}, 1);
        }
       final  BluetoothAdapter mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
        //注册广播
        mReceiver = new SingBroadcastReceiver();
        IntentFilter ifilter1= new IntentFilter(BluetoothDevice.ACTION_FOUND);
        registerReceiver(mReceiver, ifilter1);
        //扫描
        button_find.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    mBluetoothAdapter.startDiscovery();
                    lv_bluetooth.setAdapter(mArrayAdapter);
                }
            });
        //停止扫描
        button_cancel.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                mBluetoothAdapter.cancelDiscovery();
            }
        });
        }
    //广播接收器
    class SingBroadcastReceiver extends BroadcastReceiver {
        @Override
        public void onReceive(Context context, Intent intent) {
            String action = intent.getAction();
            if (BluetoothDevice.ACTION_FOUND.equals(action) ){
                // Get the BluetoothDevice object from the Intent
                BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
                //下面的代码的效果是不让已经扫描到的设备重复显示

               Boolean isRepetition=false;
                for(int i=0;i<mArrayAdapter.getCount();i++)
                {
                    if((device.getName()+"-"+device.getAddress()).equals(mArrayAdapter.getItem(i).toString()))
                    {
                        isRepetition=true;
                    }
                }
                if(!isRepetition){
                    mArrayAdapter.add(device.getName()+"-"+device.getAddress());
                }
            }
        }
    }
}