Question

我正在开发一款通过蓝牙从Arduino接收数据并将该数据发送到服务器的应用。我已经完成了这部分工作 - 一旦用户按下按钮，我就会启动BT连接，接收数据并通过异步任务将其发送到服务器：

接收数据的线程：

private class ConnectedThread extends Thread {
private final InputStream mmInStream;
private final OutputStream mmOutStream;

public ConnectedThread(BluetoothSocket socket) {

    InputStream tmpIn = null;
    OutputStream tmpOut = null;

    try {
        tmpIn = socket.getInputStream();
        tmpOut = socket.getOutputStream();
    } catch (IOException e) { }

    mmInStream = tmpIn;
    mmOutStream = tmpOut;
}

public void run() {
    Log.i("test", "Connected thread RUN");
    byte[] buffer = new byte[256];
    int bytes;

    // Keep listening to the InputStream until an exception occurs
    while (true) {
        try {
            Log.i("test", "Trying....");
            bytes = mmInStream.read(buffer);
            handler.obtainMessage(RECIEVE_MESSAGE, bytes, -1, buffer).sendToTarget();
        } catch (IOException e) {
            break;
        }
    }
}

public void write(String message) {
    Log.d(TAG, "...Data to send: " + message + "...");
    byte[] msgBuffer = message.getBytes();
    try {
        mmOutStream.write(msgBuffer);
    } catch (IOException e) {
        Log.d(TAG, "...Error data send: " + e.getMessage() + "...");
    }
}

}

ConnectedThread处理程序（接收数据，启动AsyncTask）：

private final Handler handler = new Handler() {
    public void handleMessage(android.os.Message msg) {
        switch (msg.what) {
            case RECIEVE_MESSAGE:
                byte[] readBuf = (byte[]) msg.obj;
                //String readMessage = new String(readBuf, 0, msg.arg1);
                String strIncom = new String(readBuf, 0, msg.arg1);
                sb.append(strIncom);
                int endOfLineIndex = sb.indexOf("\r\n");
                if (endOfLineIndex > 0) {
                    String sbprint = sb.substring(0, endOfLineIndex);
                    sb.delete(0, sb.length());
                    Log.i("test", "sbprint: " + sbprint);
                    sendDataToServer(sbprint);
                    txtData.setText("Data from Arduino: " + sbprint);
                }
                break;
        }
    };

};

sendDataToServer方法：

private void sendDataToServer(String dataToSend){
    if(dataToSend != null && !dataToSend.equals("")) {
        sendDataAsyncTask = new SendDataAsyncTask(MyActivity.this, dataToSend);
        sendDataAsyncTask.setSendDataListener(MyActivity.this);
        sendDataAsyncTask.execute();
    }
}

这或多或少有效。但是，现在我需要每两分钟重复一次这个过程。我已经使用TimerTask，但当设备进入休眠状态时，任务停止运行。

我猜我需要一个服务和/或一个AlarmManager来每两分钟唤醒一次设备并运行上面的代码？有什么提示吗？

Answer 1

是的，没错。您需要实现Service来执行后台作业，即执行向服务器发送数据，即使您的应用不在前台或设备显示器关闭时也是如此。

您可以在此处使用我的示例代码之一：https://xjaphx.wordpress.com/2012/07/07/create-a-service-that-does-a-schedule-task/

此外，如果您想让Service以最佳状态运行（即确保它不被系统杀死），您需要经常检查

实施BOOT_RECEIVED Intent，BroadcastReceiver，以便在设备启动时启动您的应用。
注册AlarmManager以安排检查Service是否正在运行;如果它已经死亡，你可以重新启动（唤醒）它。

Answer 2

对于偶然需要的人：

MainActivity.class：

public class MainActivity extends Activity implements OnClickListener {

private AlarmManager alarmManager;

private static final long INTERVAL = 10*1000;

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

    final Button btn = (Button) findViewById(R.id.btn);
    final Button btn2 = (Button) findViewById(R.id.btn2);
    btn.setOnClickListener(this);
    btn2.setOnClickListener(this);
}

@Override
public void onClick(View v) {
    switch (v.getId()) {
    case R.id.btn:
        setServiceAlarm();
        break;
    case R.id.btn2:
        cancelServiceAlarm();
        break;

    default:
        break;
    }
}

private void setServiceAlarm(){
    if(alarmManager == null){
        Log.i("test", "***STARTING SERVICE***");
        showToast("Starting...");
    Calendar cal = Calendar.getInstance();
    cal.add(Calendar.SECOND, 10);
    Intent intent = new Intent(MainActivity.this, AlarmReceiver.class);
    PendingIntent pendingIntent = PendingIntent.getBroadcast(this, 1, intent, 0);
    alarmManager = (AlarmManager) this.getSystemService(Context.ALARM_SERVICE);
    alarmManager.setRepeating(AlarmManager.RTC_WAKEUP, cal.getTimeInMillis(), INTERVAL, pendingIntent);
    }
}

private void cancelServiceAlarm(){
    if(alarmManager != null){
        Log.i("test", "***STOPPING SERVICE***");
        showToast("Stopping...");
        Intent intent = new Intent(MainActivity.this, AlarmReceiver.class);
    PendingIntent pendingIntent = PendingIntent.getBroadcast(this, 1, intent, 0);
    alarmManager = (AlarmManager) this.getSystemService(Context.ALARM_SERVICE);
    alarmManager.cancel(pendingIntent);
    }
}

private void showToast(String message){
    Toast.makeText(getApplicationContext(), message, Toast.LENGTH_SHORT).show();
}
}

AlarmReciever.class：

public class AlarmReceiver extends BroadcastReceiver {

@Override
public void onReceive(Context context, Intent intent) {
    // TODO Auto-generated method stub
    Log.i("test", "Alarm received...");
    Intent serviceIntent = new Intent(context, MyIntentService.class);
    serviceIntent.putExtra("date", Utils.getDateTime());
    context.startService(serviceIntent);
    //Log.i("test", "onReceive: " + Utils.getDateTime());
}
}

MyIntentService.class：

public class MyIntentService extends IntentService {

public MyIntentService() {
    super("MyIntentService");
    // TODO Auto-generated constructor stub
}

@Override
protected void onHandleIntent(Intent intent) {
    // TODO Auto-generated method stub
    final String str = intent.getStringExtra("date");
    Log.i("test", "MyIntentService " + str);
}

}

应用程序标记内的清单声明：

<service android:name=".MyIntentService"/>
<receiver android:name=".AlarmReceiver"></receiver>

定期将数据发送到服务器

2 个答案: