Bindservice错误

时间:2017-10-06 19:41:52

标签: java android android-service

我在3个活动中bindingservice,在2中效果很好,但在第3个中我遇到了错误。

这是我的服务:

public class ClientBluetoothService extends Service {
    private Handler handler = new Handler();

    private final IBinder mBinder = new LocalBinder();

    private ClientBluetooth clientBT;

    public class LocalBinder extends Binder {
        ClientBluetoothService getSerivce() {
            return ClientBluetoothService.this;
        }
    }
    public ClientBluetoothService() {
        clientBT = new ClientBluetooth();
    }

    @Override
    public IBinder onBind(Intent intent) {
        return mBinder;
    }

    public void generateToast() {
        Log.d("HERE", "Service: generateToast()");
        Toast.makeText(getApplicationContext(), "WITAJ W SERWISIE", Toast.LENGTH_SHORT).show();
    }

    public void newClient() {
        clientBT = new ClientBluetooth();
    }

    public void start() {
        clientBT.start();
    }

    public String getStatus() {
        return clientBT.getStatus();
    }

    public void disconnect() throws IOException {
        clientBT.disconnect();
    }
}

这是我的活动,我有一个错误:

public class MeasureActivity extends AppCompatActivity {

    protected boolean mBound = false;
    private ClientBluetoothService clientBluetoothService;

    private TextView textView;

    @Override
    protected void onStart() {
        super.onStart();
        Intent intent = new Intent(this, ClientBluetoothService.class);
        bindService(intent, mConnection, Context.BIND_AUTO_CREATE);
        Log.d("HERE", "Measure: onStart()");
    }

    @Override
    protected void onStop() {
        super.onStop();
        if (mBound) {
            unbindService(mConnection);
            mBound = false;
        }
    }

    @Override
    public void setTitle(CharSequence title) {
        super.setTitle(title);
    }

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

        setTitle("Measure");
        textView = (TextView)findViewById(R.id.textView);
        clientBluetoothService.generateToast();
    }

    private ServiceConnection mConnection = new ServiceConnection() {

        @Override
        public void onServiceConnected(ComponentName className, IBinder service) {

            ClientBluetoothService.LocalBinder binder = (ClientBluetoothService.LocalBinder) service;
            clientBluetoothService = binder.getSerivce();
            mBound = true;
        }

        @Override
        public void onServiceDisconnected(ComponentName arg0) {
            mBound = false;
        }
    };
}

并且我收到了错误:

  

java.lang.NullPointerException:尝试调用虚方法   “无效        com.gmail.krakow.michalt.myecg.ClientBluetoothService.generateToast()”        在空对象引用上

1 个答案:

答案 0 :(得分:3)

我不知道为什么它与其他2个活动一起工作,但是在这种情况下你很自然会得到NullPointerException。 Activity生命周期中的顺序是:

onCreate() - > onStart() - > onResume() - > onPause() - > onStop() - >和onDestroy()。 (https://developer.android.com/guide/components/activities/activity-lifecycle.html

clientBluetoothService在绑定到服务后初始化,这在onStart中完成,但是它在onCreate中使用,而onCreate总是在onStart之前运行,它给出NullPointerException。

如果你想确保在使用clientBluetoothService时初始化它,那么

mBound非常有用。