我的Java代码无法搜索附近的蓝牙设备

Question

I have written a code to list nearby Bluetooth Devices but my code is unable to detect any. According to my code, the action just starts and end and not print any device in logs when I do String action = intent.getAction(); Log.i("Action",action); in onRecieve() under BroadCastReciever.

Here is my MainActivity.java :

package com.example.findbluetoothdemo;

import androidx.appcompat.app.AppCompatActivity;

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.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.ListView;
import android.widget.TextView;

import java.util.ArrayList;

public class MainActivity extends AppCompatActivity {
    TextView statusTextView;
    ListView listView;
    Button searchButton;
    ArrayList<String> bluetoothDevices = new ArrayList<>();
    ArrayList<String> addresses = new ArrayList<>();
    ArrayAdapter arrayAdapter;

    BluetoothAdapter bluetoothAdapter;

    private final BroadcastReceiver broadcastReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            String action = intent.getAction();
            Log.i("Action",action);

            if (BluetoothAdapter.ACTION_DISCOVERY_FINISHED.equals(action)) {
                statusTextView.setText("Finished");
                searchButton.setEnabled(true);
            } else if (BluetoothDevice.ACTION_FOUND.equals(action)) {
                BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
                String name = device.getName();
                String address = device.getAddress();
                String rssi = Integer.toString(intent.getShortExtra(BluetoothDevice.EXTRA_RSSI,Short.MIN_VALUE));
                Log.i("Device Found","Nmae :"+name+" Address :"+address+" RSSI :"+rssi);

                if (!addresses.contains(address)) {
                    addresses.add(address);
                    String deviceString = "";
                    if (name==null || name.equals("")) {

                        deviceString  = address+" - RSSI "+rssi+"dBm";
                    } else {
                        deviceString = name+" - RSSI "+rssi+"dBm";
                    }
                        bluetoothDevices.add(deviceString);

                    arrayAdapter.notifyDataSetChanged();
                }

            }
        }
    };

    public void searchFunction(View view) {
        bluetoothDevices.add("ADDING NEW DEVICES...");
        statusTextView.setText("Searching...");
        searchButton.setEnabled(false);

        arrayAdapter.notifyDataSetChanged();
        bluetoothDevices.clear();
        addresses.clear();
        bluetoothAdapter.startDiscovery();




    }



    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        statusTextView = findViewById(R.id.statusTextView);
        listView = findViewById(R.id.listView);
        searchButton = findViewById(R.id.button);

        arrayAdapter = new ArrayAdapter(this,android.R.layout.simple_list_item_1,bluetoothDevices);
        listView.setAdapter(arrayAdapter);


        bluetoothAdapter = BluetoothAdapter.getDefaultAdapter();

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

    }
}

And here is AndroidManifest.xml :

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.findbluetoothdemo">

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

Answer 1

You need to ask for permission if you haven't done already.

int premissionCehck = context.checkSelfPermission("Manifest.premission.ACCES_FINE_LOCATION");
premissionCehck += context.checkSelfPermission("Manifest.premission.ACCES_FINE_LOCATION");
if (premissionCehck != 0) {
ActivityCompat.requestPermissions(activity, new String[]{Manifest.permission.ACCESS_FINE_LOCATION, Manifest.permission.ACCESS_COARSE_LOCATION}, 1001);
                    }

Take Care, If you already denied permission once, the permission request doesn't appear again, so you need to give it free in your android settings.