我的应用程序运行成功但有一些致命的错误

Question

我想尝试基本的蓝牙聊天应用程序。这是我的代码。我有听，列表视图和发送按钮。 听：搜索蓝牙设备 列表视图：显示设备列表 发送：发送消息

如果我按下听音按钮。没有问题，但如果我按列表视图或发送按钮，我会发生致命错误并关闭我的应用程序。

package com.example.duygu.btsendmessage;

import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.bluetooth.BluetoothServerSocket;
import android.bluetooth.BluetoothSocket;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.os.Handler;
import android.os.Message;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.TextView;

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

public class MainActivity extends AppCompatActivity {

    Button listen, btsend, listdevice;
    ListView listview;
    TextView textview, messageview;
    EditText entermessage;
    BluetoothAdapter myBluetoothAdapter;
    BluetoothDevice[] btArray;
    Intent enableIntent;
    SendReceive sendReceive;
    ArrayList<String> stringArrayList = new ArrayList<String>();
    ArrayAdapter<String> arrayAdapter;

    static final int STATE_LISTENING = 1;
    static final int STATE_CONNECTING = 2;
    static final int STATE_CONNECTED = 3;
    static final int STATE_CONNECTION_FAILED = 4;
    static final int STATE_MESSAGE_RECEIVER = 5;
    int REQUEST_ENABLE_BLUETOOTH = 1;


  private static final String APP_NAME = "BTCom";
    private static final UUID MYUUID = UUID.fromString("00001101-0000-1000-8000-00805F9B34FB");




    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);



        myBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
        findviewbyidset();

        if (!myBluetoothAdapter.isEnabled()) {
            enableIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
            startActivityForResult(enableIntent, REQUEST_ENABLE_BLUETOOTH);

        }
        implementListeners();




    }




    private void findviewbyidset() {
      listen = (Button) findViewById(R.id.listen);
        btsend = (Button) findViewById(R.id.btsend);
        listdevice = (Button) findViewById(R.id.listdevice);
        listview = (ListView) findViewById(R.id.listview);
        textview = (TextView) findViewById(R.id.textview);
        messageview = (TextView) findViewById(R.id.messageview);
        entermessage = (EditText) findViewById(R.id.entermessage);
    }

    private void implementListeners() {
        listdevice.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Set<BluetoothDevice> bt = myBluetoothAdapter.getBondedDevices();
                String[] strings = new String[bt.size()];
                //btArray=new BluetoothDevice[bt.size()];
                int index = 0;
                if (bt.size() > 0) {
                    for (BluetoothDevice device : bt) {
                        strings[index] = device.getName();
                        index++;
                    }

                    ArrayAdapter<String> arrayAdapter = new ArrayAdapter<String>(getApplicationContext(), android.R.layout.simple_list_item_1, strings);
                    listview.setAdapter(arrayAdapter);
                }
            }
        });

     listen.setOnClickListener(new View.OnClickListener() {
          @Override
          public void onClick(View view) {
              ServerClass serverClass=new ServerClass();
              serverClass.start();
          }
      });


       listview.setOnItemClickListener(new AdapterView.OnItemClickListener() {
           @Override
           public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
               ClientClass clientClass= new ClientClass(btArray[i]);
               clientClass.start();
               textview.setText("Connecting");
           }
       });

        btsend.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                String string= String.valueOf(entermessage.getText());
                sendReceive.write(string.getBytes());
            }
        });

    }

    Handler handler = new Handler(new Handler.Callback() {
        @Override
        public boolean handleMessage(Message msg) {
            switch (msg.what) {
                case STATE_LISTENING:
                    textview.setText("Listening");
                    break;
                case STATE_CONNECTING:
                    textview.setText("Connecting");
                    break;
                case STATE_CONNECTED:
                    textview.setText("Connected");
                    break;
                case STATE_CONNECTION_FAILED:
                    textview.setText("Connection Failed");
                    break;
                case STATE_MESSAGE_RECEIVER:
                    byte[] readBuff= (byte[]) msg.obj;
                    String tempMsg=new String(readBuff,0,msg.arg1);
                    messageview.setText(tempMsg);
                    break;

            }


            return true;
        }
    });


    private class ServerClass extends Thread {
        private BluetoothServerSocket serverSocket;

        public ServerClass() {
            try {
                serverSocket = myBluetoothAdapter.listenUsingRfcommWithServiceRecord(APP_NAME, MYUUID);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

        public void run(){
            BluetoothSocket socket=null;
            while(socket==null){
                try{
                    Message message=Message.obtain();
                    message.what=STATE_CONNECTING;
                    handler.sendMessage(message);
                    socket=serverSocket.accept();
                }
                catch(IOException e){
                    e.printStackTrace();
                    Message message=Message.obtain();
                    message.what=STATE_CONNECTING;
                    handler.sendMessage(message);
                }
                if(socket!=null){
                    Message message=Message.obtain();
                    message.what=STATE_CONNECTED;
                    handler.sendMessage(message);
                    sendReceive=new SendReceive(socket);
                    sendReceive.start();
                    break;
                }
            }
        }
    }

    private class ClientClass extends Thread{
        private BluetoothDevice device;
        private BluetoothSocket socket;

        public ClientClass (BluetoothDevice device1){
            device=device1;
            try{
                socket=device.createRfcommSocketToServiceRecord(MYUUID);
            } catch(IOException e){
                e.printStackTrace();
            }

        }

        public void run(){
            try{
                socket.connect();
                Message message=Message.obtain();
                message.what=STATE_CONNECTED;
                handler.sendMessage(message);
                sendReceive=new SendReceive(socket);
                sendReceive.start();
            }
            catch(IOException e){
                e.printStackTrace();
                Message message=Message.obtain();
                message.what=STATE_CONNECTION_FAILED;
                handler.sendMessage(message);
            }
        }
    }

        private class  SendReceive extends Thread{


        private  BluetoothSocket bluetoothSocket;
        private  InputStream inputStream;
        private  OutputStream outputStream;




        public SendReceive (BluetoothSocket socket){
            bluetoothSocket=socket;
            InputStream tempIn =null;
            OutputStream tempOut=null;

            try {
                tempIn=bluetoothSocket.getInputStream();
                tempOut=bluetoothSocket.getOutputStream();
            } catch (IOException e) {
                e.printStackTrace();

            }


        }


        public void run(){
            byte[] buffer=new byte[1024];
            int bytes;
            while(true){
                try {
                    bytes=inputStream.read(buffer);
                    handler.obtainMessage(STATE_MESSAGE_RECEIVER,bytes,-1,buffer).sendToTarget();
                } catch (IOException e) {
                    e.printStackTrace();

                }
            }

        }

        public void write(byte[] bytes){
            try {
                outputStream.write(bytes);
            } catch (IOException e) {
                e.printStackTrace();
            }

        }
 }

}

我的Fattal Erorrs：

 E/AndroidRuntime: FATAL EXCEPTION: main
                  Process: com.example.duygu.btsendmessage, PID: 7917
                  java.lang.NullPointerException: Attempt to read from null array
                      at com.example.duygu.btsendmessage.MainActivity$3.onItemClick(MainActivity.java:125)
                      at android.widget.AdapterView.performItemClick(AdapterView.java:310)
                      at android.widget.AbsListView.performItemClick(AbsListView.java:1188)
                      at android.widget.AbsListView$PerformClick.run(AbsListView.java:3100)
                      at android.widget.AbsListView$3.run(AbsListView.java:4091)
                      at android.os.Handler.handleCallback(Handler.java:739)
                      at android.os.Handler.dispatchMessage(Handler.java:95)
                      at android.os.Looper.loop(Looper.java:148)
                      at android.app.ActivityThread.main(ActivityThread.java:5525)
                      at java.lang.reflect.Method.invoke(Native Method)
                      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:730)
                      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:620)

修改1

我更改了这部分代码并修复了列表视图按钮，但发送按钮有一些错误。

 private void implementListeners() {
    listdevice.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Set<BluetoothDevice> bt = myBluetoothAdapter.getBondedDevices();
            String[] strings = new String[bt.size()];
            btArray=new BluetoothDevice[bt.size()];
            int index = 0;
            if (bt.size() > 0) {
                for (BluetoothDevice device : bt) {
                    btArray[index] = device;
                    strings[index] = device.getName();
                    index++;
                }
                ArrayAdapter<String> arrayAdapter = new ArrayAdapter<String>(getApplicationContext(), android.R.layout.simple_list_item_1, strings);
                listview.setAdapter(arrayAdapter);
            }
        }
    });

致命错误

E/AndroidRuntime: FATAL EXCEPTION: main
                  Process: com.example.duygu.btsendmessage, PID: 16656
                  java.lang.NullPointerException: Attempt to invoke virtual method 'void com.example.duygu.btsendmessage.MainActivity$SendReceive.write(byte[])' on a null object reference
                      at com.example.duygu.btsendmessage.MainActivity$4.onClick(MainActivity.java:135)
                      at android.view.View.performClick(View.java:5201)
                      at android.view.View$PerformClick.run(View.java:21215)
                      at android.os.Handler.handleCallback(Handler.java:739)
                      at android.os.Handler.dispatchMessage(Handler.java:95)
                      at android.os.Looper.loop(Looper.java:148)
                      at android.app.ActivityThread.main(ActivityThread.java:5525)
                      at java.lang.reflect.Method.invoke(Native Method)
                      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:730)
                      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:620)

修改2

我更改了所有搜索代码。

package com.example.duygu.btsendmessage;

import android.Manifest;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.bluetooth.BluetoothServerSocket;
import android.bluetooth.BluetoothSocket;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.os.Handler;
import android.os.Message;
import android.support.v4.app.ActivityCompat;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.TextView;

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

public class MainActivity extends AppCompatActivity {

    Button listen, btsend, listdevice;
    ListView listview;
    TextView textview, messageview;
    EditText entermessage;
    BluetoothAdapter myBluetoothAdapter;
    BluetoothDevice[] btArray;
    Intent enableIntent;
    SendReceive sendReceive;


    static final int STATE_LISTENING = 1;
    static final int STATE_CONNECTING = 2;
    static final int STATE_CONNECTED = 3;
    static final int STATE_CONNECTION_FAILED = 4;
    static final int STATE_MESSAGE_RECEIVER = 5;
    int REQUEST_ENABLE_BLUETOOTH = 1;


  private static final String APP_NAME = "BTCom";
    private static final UUID MYUUID = UUID.fromString("00001101-0000-1000-8000-00805F9B34FB");

    ArrayList<String> stringArrayList = new ArrayList<String>();
    ArrayAdapter<String> arrayAdapter;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        myBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
        IntentFilter intentFilter = new IntentFilter(BluetoothDevice.ACTION_FOUND);
        registerReceiver(myReceiver,intentFilter);
        findviewbyidset();

        int MY_PERMISSIONS_REQUEST_ACCESS_COARSE_LOCATION = 1;
        ActivityCompat.requestPermissions(MainActivity.this,
                new String[]{Manifest.permission.ACCESS_COARSE_LOCATION},MY_PERMISSIONS_REQUEST_ACCESS_COARSE_LOCATION);


        implementListeners();
    }


    private void findviewbyidset() {
      listen = (Button) findViewById(R.id.listen);
        btsend = (Button) findViewById(R.id.btsend);
        listdevice = (Button) findViewById(R.id.listdevice);
        listview = (ListView) findViewById(R.id.listview);
        textview = (TextView) findViewById(R.id.textview);
        messageview = (TextView) findViewById(R.id.messageview);
        entermessage = (EditText) findViewById(R.id.entermessage);
    }

    private void implementListeners() {
        listdevice.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                myBluetoothAdapter.startDiscovery();

                if (!myBluetoothAdapter.isEnabled()) {
                    enableIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
                    startActivityForResult(enableIntent, REQUEST_ENABLE_BLUETOOTH);

                }
             /*   Set<BluetoothDevice> bt = myBluetoothAdapter.getBondedDevices();
                String[] strings = new String[bt.size()];
                btArray=new BluetoothDevice[bt.size()];
                int index = 0;
                if (bt.size() > 0) {
                    for (BluetoothDevice device : bt) {
                        btArray[index] = device;
                        strings[index] = device.getName();
                        index++;
                    }
                    ArrayAdapter<String> arrayAdapter = new ArrayAdapter<String>(getApplicationContext(), android.R.layout.simple_list_item_1, strings);
                    listview.setAdapter(arrayAdapter);
                }*/
            }
        });

     listen.setOnClickListener(new View.OnClickListener() {
          @Override
          public void onClick(View view) {

              ServerClass serverClass=new ServerClass();
              serverClass.start();
          }
      });


       listview.setOnItemClickListener(new AdapterView.OnItemClickListener() {
           @Override
           public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
               ClientClass clientClass= new ClientClass(device);
               clientClass.start();
               textview.setText("Connecting");
           }
       });

        btsend.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                String string= String.valueOf(entermessage.getText());

                sendReceive.write(string.getBytes());
            }
        });
    }

    Handler handler = new Handler(new Handler.Callback() {
        @Override
        public boolean handleMessage(Message msg) {
            switch (msg.what) {
                case STATE_LISTENING:
                    textview.setText("Listening");
                    break;
                case STATE_CONNECTING:
                    textview.setText("Connecting");
                    break;
                case STATE_CONNECTED:
                    textview.setText("Connected");
                    break;
                case STATE_CONNECTION_FAILED:
                    textview.setText("Failed");
                    break;
                case STATE_MESSAGE_RECEIVER:
                    byte[] readBuff= (byte[]) msg.obj;
                    String tempMsg=new String(readBuff,0,msg.arg1);
                    messageview.setText(tempMsg);
                    break;
            }

            return true;
        }
    });

    private final BroadcastReceiver myReceiver = new BroadcastReceiver() {
        public void onReceive(Context context, Intent intent) {
            String action = intent.getAction();
            if (BluetoothDevice.ACTION_FOUND.equals(action)) {
                BluetoothDevice device = intent
                        .getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
                stringArrayList.add(device.getName() + "\n" + device.getAddress());
                Log.i("BT", device.getName() + "\n" + device.getAddress());
                listview.setAdapter(new ArrayAdapter<String>(context,
                        android.R.layout.simple_list_item_1, stringArrayList));
            }
        }
    };
    private class ServerClass extends Thread {
        private BluetoothServerSocket serverSocket;

        public ServerClass() {
            try {
                serverSocket = myBluetoothAdapter.listenUsingRfcommWithServiceRecord(APP_NAME, MYUUID);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

        public void run(){
            BluetoothSocket socket=null;
            while(socket==null){
                try{
                    Message message=Message.obtain();
                    message.what=STATE_CONNECTING;
                    handler.sendMessage(message);
                    socket=serverSocket.accept();
                }
                catch(IOException e){
                    e.printStackTrace();
                    Message message=Message.obtain();
                    message.what=STATE_CONNECTING;
                    handler.sendMessage(message);
                }
                if(socket!=null){
                    Message message=Message.obtain();
                    message.what=STATE_CONNECTED;
                    handler.sendMessage(message);
                    sendReceive=new SendReceive(socket);
                    sendReceive.start();
                    break;
                }
            }
        }
    }

    private class ClientClass extends Thread{
        private BluetoothDevice device;
        private BluetoothSocket socket;

        public ClientClass (BluetoothDevice device1){
            device=device1;
            try{
                socket=device.createRfcommSocketToServiceRecord(MYUUID);
            } catch(IOException e){
                e.printStackTrace();
            }
        }

        public void run(){
            try{
                socket.connect();
                Message message=Message.obtain();
                message.what=STATE_CONNECTED;
                handler.sendMessage(message);
                sendReceive=new SendReceive(socket);
                sendReceive.start();
            }
            catch(IOException e){
                e.printStackTrace();
                Message message=Message.obtain();
                message.what=STATE_CONNECTION_FAILED;
                handler.sendMessage(message);
            }
        }
    }

        private class  SendReceive extends Thread{


        private  BluetoothSocket bluetoothSocket;
        private  InputStream inputStream;
        private  OutputStream outputStream;


        public SendReceive (BluetoothSocket socket){
            bluetoothSocket=socket;
            InputStream tempIn =null;
            OutputStream tempOut=null;

            try {
                tempIn=bluetoothSocket.getInputStream();
                tempOut=bluetoothSocket.getOutputStream();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }


        public void run(){
            byte[] buffer=new byte[1024];
            int bytes;
            while(true){
                try {
                    bytes=inputStream.read(buffer);
                    handler.obtainMessage(STATE_MESSAGE_RECEIVER,bytes,-1,buffer).sendToTarget();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }

        public void write(byte[] bytes){
            try {
                outputStream.write(bytes);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
 }
}

如何更改此代码：

 listview.setOnItemClickListener(new AdapterView.OnItemClickListener() {
           @Override
           public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
               ClientClass clientClass= new ClientClass(**????**);
               clientClass.start();
               textview.setText("Connecting");
           }
       });

Answer 1

您正在使用implementListeners（）函数向ArrayAdapter构造函数发送一个空的String数组。

将setOnClickListerner更改为

private void implementListeners() {
    listdevice.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Set<BluetoothDevice> bt = myBluetoothAdapter.getBondedDevices();
            String[] strings = new String[bt.size()];
            btArray=new BluetoothDevice[bt.size()];
            int index = 0;
            if (bt.size() > 0) {
                for (BluetoothDevice device : bt) {
                    btArray[index] = device;
strings[index] = bt.getName();
                    index++;
                }
                ArrayAdapter<String> arrayAdapter = new ArrayAdapter<String>(getApplicationContext(), android.R.layout.simple_list_item_1, strings);
                listview.setAdapter(arrayAdapter);
            }
        }
    });

回答编辑2

声明BluetoothDevice的ArrayList

ArrayList<BluetoothDevice> list = new ArrayList<>();

添加此list.add（设备）;在

private final BroadcastReceiver myReceiver = new BroadcastReceiver() {
public void onReceive(Context context, Intent intent) {
    String action = intent.getAction();
           if (BluetoothDevice.ACTION_FOUND.equals(action)) {
            BluetoothDevice device = intent
                    .getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
            list.add(device); // this line here
            stringArrayList.add(device.getName() + "\n" + device.getAddress());
            Log.i("BT", device.getName() + "\n" + device.getAddress());
            listview.setAdapter(new ArrayAdapter<String>(context,
                    android.R.layout.simple_list_item_1, stringArrayList));
        }
    }
};

最后将listview.setOnItemClickListener更改为

listview.setOnItemClickListener(new AdapterView.OnItemClickListener() {
    @Override
    public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
        ClientClass clientClass= new ClientClass(list.get(i));
        clientClass.start();
        textview.setText("Connecting");
    }
});