Question

这是我的代码

import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.Toast;
import java.util.ArrayList;

public class MainActivity extends AppCompatActivity {

    private final BroadcastReceiver mReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            String action = intent.getAction();

            if (BluetoothDevice.ACTION_FOUND.equals(action)) {                
                BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
                devices.add(device.getName());                
            } else if (BluetoothAdapter.ACTION_DISCOVERY_FINISHED.equals(action)) {
                mBtAdapter.startDiscovery();
                Toast.makeText(MainActivity.this,"Discovering "+devices.size(),Toast.LENGTH_SHORT).show();
                ArrayAdapter arrayAdapter=new ArrayAdapter(MainActivity.this,android.R.layout.simple_list_item_1,devices);
                listView.setAdapter(arrayAdapter);
                }
            }

    };

    ListView listView;
    ArrayList<String> devices;
    private BluetoothAdapter mBtAdapter;  

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        listView=(ListView) findViewById(R.id.listView);
        devices=new ArrayList<String>();

        IntentFilter filter = new IntentFilter(BluetoothDevice.ACTION_FOUND);
        this.registerReceiver(mReceiver, filter);

        filter = new IntentFilter(BluetoothAdapter.ACTION_DISCOVERY_FINISHED);
        this.registerReceiver(mReceiver, filter);

        mBtAdapter = BluetoothAdapter.getDefaultAdapter();

        if(!mBtAdapter.isEnabled()){
            mBtAdapter.enable();
        }

        mBtAdapter.startDiscovery();        
    }

    @Override
    protected void onDestroy(){
        super.onDestroy();
        mBtAdapter.cancelDiscovery();
        unregisterReceiver(mReceiver);
    }
}

问题是它始终显示发现0 ，因为设备的大小arrayList始终为0.但是手机检测到附近的可用设备，如下图Screenshot of phone bluetooth settings所示。我认为我的应用广播接收器没有检测到可用的蓝牙设备，因为我的代码中有错误。请帮助我

Answer 1

您不必两次注册接收器，意图过滤器可以执行多个操作。

IntentFilter intentFilter = new IntentFilter();
intentFilter.addAction(BluetoothDevice.ACTION_FOUND);
intentFilter.addAction(BluetoothAdapter.ACTION_DISCOVERY_FINISHED);
registerReceiver(yourReceiver, intentFilter);

检查您是否具有扫描所需的权限：

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

在正常模式下，并非所有蓝牙设备都可以被发现，请查看BluetoothLeScanner和蓝牙适配器的startLeScan方法：

BluetoothManager bluetoothManager = (BluetoothManager) getSystemService(Context.BLUETOOTH_SERVICE); 
BluetoothAdapter bluetoothAdapter = bluetoothManager.getAdapter();

bluetoothAdapter.getBluetoothLeScanner().startScan(yourCallback); // API 21+
bluetoothAdapter.startLeScan(yourCallback); // API 18+

此外，打开设备上的蓝牙需要一些时间，您应该听取蓝牙状态更改并在打开并准备使用后启动发现，请查看此answer。

应用广播接收器未检测到附近可用的蓝牙设备，但电话检测到

1 个答案: