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Я пытаюсь подключить свое приложение Android к моему Arduino Uno по Bluetooth. Чтобы сделать соединение общим для всего приложения, я создал службу, в которой я реализовал свои функции Bluetooth. Проблема в том, что моя функция sendData вызывает ошибку и не имеет представления о том, как ее разрешить.Попытка вызвать виртуальный метод 'void java.io.OutputStream.write (byte [])' на ссылке нулевого объекта
Пожалуйста, помогите мне. Спасибо заранее :)
Вот мой MainActivity.java:
package llg.trashbin;
import java.io.IOException;
import java.io.OutputStream;
import java.util.UUID;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.view.View.OnClickListener;
import android.widget.ImageButton;
import android.widget.TextView;
import android.widget.Toast;
import android.content.Intent;
public class MainActivity extends AppCompatActivity {
public int objectOut = 0;
communicationEnabled mCommunicate = new communicationEnabled();
Button bottle, emballages, papier;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Intent mBluetooth = new Intent(MainActivity.this, BluetoothConnectService.class);
startService(mBluetooth);
bottle = (Button) findViewById(R.id.bottle);
emballages = (Button) findViewById(R.id.emballages);
papier = (Button) findViewById(R.id.papier);
bottle.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
objectOut = 2;
mCommunicate.MessageSent();
}
});
emballages.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
objectOut = 3;
mCommunicate.MessageSent();
}
});
papier.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
objectOut = 5;
mCommunicate.MessageSent();
}
});
}
public class communicationEnabled extends BluetoothConnectService {
public String hello = "1";
public void MessageSent() {
sendData(hello);
}
}
}
BluetoothConnectService.java:
package llg.trashbin;
import android.app.Service;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.bluetooth.BluetoothSocket;
import android.content.Intent;
import android.os.IBinder;
import android.util.Log;
import java.io.IOException;
import java.io.OutputStream;
import java.util.UUID;
public class BluetoothConnectService extends Service {
private static final String TAG = "Tripoubelle";
public static final int REQUEST_ENABLE_BT = 1;
public BluetoothAdapter btAdapter = null;
public BluetoothSocket btSocket = null;
public OutputStream outStream = null;
private static final UUID MY_UUID = UUID.fromString("00001101-0000-1000-8000-00805F9B34FB");
private static String address = "00:13:EF:00:00:4C";
@Override
public IBinder onBind(Intent intent) {
return null;
}
@Override
public void onCreate() {
Log.d(TAG, "In onCreate()");
super.onCreate();
btAdapter = BluetoothAdapter.getDefaultAdapter();
checkBTState();
Log.d(TAG, "...In onResume - Attempting client connect...");
BluetoothDevice device = btAdapter.getRemoteDevice(address);
try {
btSocket = device.createRfcommSocketToServiceRecord(MY_UUID);
} catch (IOException e) {
errorExit("Fatal Error", "In onResume() and socket create failed: " + e.getMessage() + ".");
}
btAdapter.cancelDiscovery();
Log.d(TAG, "...Connecting to Remote...");
try {
btSocket.connect();
Log.d(TAG, "...Connection established and data link opened...");
} catch (IOException e) {
try {
btSocket.close();
} catch (IOException e2) {
errorExit("Fatal Error", "In onResume() and unable to close socket during connection failure" + e2.getMessage() + ".");
}
}
Log.d(TAG, "...Creating Socket...");
try {
outStream = btSocket.getOutputStream();
} catch (IOException e) {
errorExit("Fatal Error", "In onResume(), input and output stream creation failed:" + e.getMessage() + ".");
}
}
public void onPause() {
Log.d(TAG, "...In onPause()...");
if (outStream != null) {
try {
outStream.flush();
} catch (IOException e) {
errorExit("Fatal Error", "In onPause() and failed to flush output stream: " + e.getMessage() + ".");
}
}
try {
btSocket.close();
} catch (IOException e2) {
errorExit("Fatal Error", "In onPause() and failed to close socket." + e2.getMessage() + ".");
}
}
public void checkBTState() {
// Check for Bluetooth support and then check to make sure it is turned on
// Emulator doesn't support Bluetooth and will return null
if(btAdapter==null) {
errorExit("Fatal Error", "Bluetooth Not supported. Aborting.");
} else {
if (btAdapter.isEnabled()) {
Log.d(TAG, "...Bluetooth is enabled...");
} else {
//Prompt user to turn on Bluetooth
Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
startActivity(enableBtIntent);
}
}
}
private void errorExit(String title, String message){
Toast msg = Toast.makeText(getBaseContext(),
title + " - " + message, Toast.LENGTH_SHORT);
msg.show();
finish();
}
public void sendData(String message) {
byte[] msgBuffer = message.getBytes();
Log.d(TAG, "...Sending data: " + message + "...");
try {
outStream.write(msgBuffer);
} catch (IOException e) {
String msg = "In onResume() and an exception occurred during write: " + e.getMessage();
if (address.equals("00:13:EF:00:00:4C"))
msg = msg + ".\n\nUpdate your server address from 00:13:EF:00:00:4C to the correct address on line 37 in the java code";
msg = msg + ".\n\nCheck that the SPP UUID: " + MY_UUID.toString() + " exists on server.\n\n";
errorExit("Fatal Error", msg);
}
}
}
Здесь ошибка:
12-27 10:21:52.511 1178-1178/llg.trashbin E/AndroidRuntime: FATAL EXCEPTION: main
Process: llg.trashbin, PID: 117
java.lang.NullPointerException: Attempt to invoke virtual method 'void java.io.OutputStream.write(byte[])' on a null object reference
at llg.trashbin.BluetoothConnectService.sendData(BluetoothConnectService.java:125)
at llg.trashbin.MainActivity$communicationEnabled.MessageSent(MainActivity.java:103)
at llg.trashbin.MainActivity$2.onClick(MainActivity.java:71)
at android.view.View.performClick(View.java:5702)
at android.widget.TextView.performClick(TextView.java:10888)
at android.view.View$PerformClick.run(View.java:22541)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:158)
at android.app.ActivityThread.main(ActivityThread.java:7229)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120)
Edit:
Я поставил код функции sentData в если/другое заявление для того, чтобы проверить, если назначенная строка была пустой:
public void sendData(String message) {
if (message != null) {
Log.d(TAG, "sent data isn't null !");
byte[] msgBuffer = message.getBytes();
Log.d(TAG, "...Sending data: " + message + "...");
try {
outStream.write(msgBuffer);
} catch (IOException e) {
String msg = "In onResume() and an exception occurred during write: " + e.getMessage();
if (address.equals("00:13:EF:00:00:4C"))
msg = msg + ".\n\nUpdate your server address from 00:13:EF:00:00:4C to the correct address on line 37 in the java code";
msg = msg + ".\n\nCheck that the SPP UUID: " + MY_UUID.toString() + " exists on server.\n\n";
//errorExit("Fatal Error", msg);
}
}
else {
Log.d(TAG, "sent data is null !");
}
}
И у меня был результат POSITIF: назначенная строка не была нулевой!
Вот окно отладки:
12-27 12:53:24.661 8183-8183/llg.trashbin D/Tripoubelle: sent data isn't null !
код, который зависит от успех предыдущего кода в блоке 'try' должен находиться внутри блока' try'. Часто это означает, что весь метод должен генерировать исключение, а не ловить его. Не пишите такой код. – EJP