java BroadcastReceiver OnReceive无法正常工作

Question

我正在尝试编写我的第一个Android应用程序。我想在列表视图中显示附近的所有蓝牙设备。但我的应用程序总是空的，在列表视图中从不显示任何内容。 经过一些调试，我发现BroadcastReceiver onReceive从未被调用。我读了很多类似的帖子，但似乎什么都不管用。根据来自https://developer.安卓.com/reference/安卓/content/BroadcastReceiver的文档，它应该在广播接收器接收到意图广播时被调用。但出于某种原因，它没有。我在清单上有所有必要的权限。我找不到问题。 有人知道为什么我的代码不起作用吗

主要活动。爪哇：

package com.example.bluetoothdevicelist;

import 安卓.Manifest;
import 安卓.bluetooth.BluetoothAdapter;
import 安卓.bluetooth.BluetoothDevice;
import 安卓.content.BroadcastReceiver;
import 安卓.content.Context;
import 安卓.content.IntentFilter;
import 安卓.support.v7.app.AppCompatActivity;
import 安卓.os.Bundle;
import 安卓.os.Build;
import 安卓.view.Menu;
import 安卓.view.View;
import 安卓.util.Log;
import 安卓.content.Intent;
import 安卓.widget.AdapterView;
import 安卓.widget.ArrayAdapter;
import 安卓.widget.ListView;
import java.util.ArrayList;
import java.util.Set;


public class MainActivity extends AppCompatActivity {

    private ListView listView;
    private ArrayList<String> mDeviceList = new ArrayList<String>();
    private BluetoothAdapter mBluetoothAdapter;
    private ArrayAdapter mArrayAdapter;
    private BluetoothDevice bt;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Log.d("BT", "start!");
        listView = (ListView) findViewById(R.id.listView);

        mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();

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

        //Turn Bluetooth on
        if (!mBluetoothAdapter.isEnabled()) {
            Intent enableBTIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
            startActivity(enableBTIntent);
        }
        mBluetoothAdapter.startDiscovery();
    }


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


    public BroadcastReceiver mReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            String action = intent.getAction();
            Log.d("BT", "I am here!");
            if (action.equals(BluetoothDevice.ACTION_FOUND)) {
                BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
                mDeviceList.add(device.getName() + "\n" + device.getAddress());
                mDeviceList.add("It should work");
                Log.d("BT", device.getName() + "\n" + device.getAddress());

                mArrayAdapter = (new ArrayAdapter<String>(context, 安卓.R.layout.simple_list_item_1, mDeviceList));
                listView.setAdapter(mArrayAdapter);
            }
        }
    };
}

清单：

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

    <uses-feature 安卓:name="安卓.hardware.bluetooth" />
    <uses-permission 安卓:name="安卓.permission.BLUETOOTH" />
    <uses-permission 安卓:name="安卓.permission.BLUETOOTH_ADMIN" />
    <uses-permission 安卓:name="安卓.permission.ACCESS_COARSE_LOCATION" />
    <uses-permission 安卓:name="安卓.permission.ACCESS_FINE_LOCATION" />
    <uses-permission 安卓:name="安卓.permission.BLUETOOTH_PRIVILEGED" />

    <application
        安卓:allowBackup="true"
        安卓:icon="@mipmap/ic_launcher"
        安卓:label="@string/app_name"
        安卓:roundIcon="@mipmap/ic_launcher_round"
        安卓:supportsRtl="true"
        安卓:theme="@style/AppTheme">
        <activity 安卓:name=".MainActivity">
            <intent-filter>
                <action 安卓:name="安卓.intent.action.MAIN" />

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

</manifest>

梅因。xml:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:安卓="http://schemas.安卓.com/apk/res/安卓"
    xmlns:tools="http://schemas.安卓.com/tools"
    安卓:layout_width="match_parent"
    安卓:layout_height="match_parent"
    tools:context="com.example.bluetoothdevicelist.MainActivity" >

    <ListView
        安卓:layout_width="wrap_content"
        安卓:layout_height="wrap_content"
        安卓:id="@+id/listView"/>

Answer 1

艾西弗先生可能会无效！检查初始化。 BroadcastReceiver mReceiver=新的BroadcastReceiver（）； registerReceiver（mrReceiver，过滤器）

Answer 2

请打开GPS并重试。请确保您向您的用户请求位置许可

原因：在Android 6.0中，蓝牙发现需要位置许可

更多参考资料：

1. https://developer.android.com/guide/topics/connectivity/bluetooth
2. https://getlief.zendesk.com/hc/en-us/articles/360007600233-Why-does-Android-require-Location-Permissions-for-Bluetooth-

Answer 3

更新：对于所有有类似问题的人：GPS/位置需要在你的设备上打开！关闭时，它不会在列表视图中显示任何内容