Android Studio“变量”示例'可能尚未初始化“现在该怎么办？

Question

我的问题是Android Studio说“变量'示例'可能尚未初始化”。这适用于这两个：

private final BluetoothSocket bluetoothSocket;
private final BluetoothDevice bluetoothDevice;

在第57行，bluetoothDevice是红色下划线，并说“无法为最终变量'bluetoothDevice'赋值”

希望有人可以帮忙:)

这是我的BT_Classic.java：

    package com.car.bluetooth.bluetoothcar;

import androidx.appcompat.app.AppCompatActivity;

import android.app.ProgressDialog;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.bluetooth.BluetoothSocket;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.ListView;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Set;
import java.util.UUID;



public class BT_Classic extends AppCompatActivity {

private Button pairedButton;
private Button discoveredButton;
private Button btonButton;
private Button btoffButton;
private ProgressDialog progress;
ListView listView;
private final BluetoothSocket bluetoothSocket;
private final BluetoothDevice bluetoothDevice;


private final static UUID uuid = UUID.fromString("fc5ffc49-00e3-4c8b-9cf1-6b72aad1001a");


private ArrayList<String> mDeviceList = new ArrayList<String>();

BluetoothAdapter btAdapter = BluetoothAdapter.getDefaultAdapter();


//BLUETOOTH VERBINDUNG


private static final int REQUEST_ENABLED = 0;
private static final int REQUEST_DISCOVERABLE = 0;

    private class ConnectingThread extends Thread {

        public ConnectingThread(BluetoothDevice device) {


            BluetoothSocket temp = null;
            BluetoothDevice bluetoothDevice = device;

            // Get a BluetoothSocket to connect with the given BluetoothDevice
            try {
                temp = bluetoothDevice.createRfcommSocketToServiceRecord(uuid);
            } catch (IOException e) {
                e.printStackTrace();
            }
            bluetoothSocket = temp;

        }


            public void run() {
        // Cancel any discovery as it will slow down the connection
        btAdapter.cancelDiscovery();

        try {
            // This will block until it succeeds in connecting to the device
            // through the bluetoothSocket or throws an exception
            bluetoothSocket.connect();
        } catch (IOException connectException) {
            connectException.printStackTrace();
            try {
                bluetoothSocket.close();
            } catch (IOException closeException) {
                closeException.printStackTrace();
            }
        }

        // Code to manage the connection in a separate thread
    /*
        manageBluetoothConnection(bluetoothSocket);
    */
    }

    // Cancel an open connection and terminate the thread
    public void cancel() {
        try {
            bluetoothSocket.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

}





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


    pairedButton = (Button) findViewById(R.id.pairedButton);
    discoveredButton = (Button) findViewById(R.id.discoveredButton);
    btonButton = (Button) findViewById(R.id.btonButton);
    btoffButton = (Button) findViewById(R.id.btoffButton);


    listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
            String  itemValue = (String) listView.getItemAtPosition(position);
            String MAC = itemValue.substring(itemValue.length() - 17);
            BluetoothDevice bluetoothDevice = btAdapter.getRemoteDevice(MAC);
            // Initiate a connection request in a separate thread
            ConnectingThread t = new ConnectingThread(bluetoothDevice);
            t.start();
        }
    });

    //Pairing Button

    pairedButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Set<BluetoothDevice> pairedDevices = btAdapter.getBondedDevices();

            ArrayList<String> devices = new ArrayList<String>();

            for (BluetoothDevice bt : pairedDevices){
                devices.add(bt.getName());
                devices.add(bt.getAddress());

            }

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








    discoveredButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

            if(!btAdapter.isDiscovering()){
                Intent bton = new Intent(BluetoothAdapter.ACTION_REQUEST_DISCOVERABLE);
                startActivityForResult(bton, REQUEST_DISCOVERABLE);
            }


        }
    });

    btonButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Intent bton = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
            startActivityForResult(bton, REQUEST_ENABLED);
        }
    });

    btoffButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            btAdapter.disable();
        }
    });










}
}

Answer 1

简单地说就是这样;

private class ConnectingThread extends Thread {

public ConnectingThread(BluetoothDevice device) {



    BluetoothSocket temp = null;
    BluetoothDevice bluetoothDevice = device;

    // Get a BluetoothSocket to connect with the given BluetoothDevice
    try {
        temp = bluetoothDevice.createRfcommSocketToServiceRecord(uuid);
    } catch (IOException e) {
        e.printStackTrace();
    }
    bluetoothSocket = temp;


}

Answer 2

定义最终变量需要在同一个类的构造函数中进行内联实例化或实例化。我的意思是以下几行：

private final BluetoothSocket bluetoothSocket;
private final BluetoothDevice bluetoothDevice;

这些变量必须在BT_Classic的构造函数中初始化。