Question

您好我是Android编程的新手。我正在为学校编写应用程序，我需要将Accelerometer数据保存到txt文件。问题是当我锁定屏幕或打开屏幕保存时，数据记录停止。你能给我建议吗？

这是我的代码：

package emzet.data2text;

import android.app.Activity;
import android.content.Context;
import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;
import android.os.Bundle;
import android.os.Environment;
import android.os.PowerManager;
import android.view.View;
import android.widget.Button;

import java.io.FileWriter;
import java.io.IOException;
import java.text.SimpleDateFormat;


public class MainActivity extends Activity implements SensorEventListener {

private SensorManager sensorManager;
private Sensor accelerometer;
private FileWriter writer;
private Button btnStart, btnStop;
String root = Environment.getExternalStorageDirectory().toString();

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    btnStart = (Button) findViewById(R.id.btnStart);
    btnStop = (Button) findViewById(R.id.btnStop);
    btnStart.setEnabled(true);
    btnStop.setEnabled(true);
    //PowerManager mgr = (PowerManager)this.getSystemService(Context.POWER_SERVICE);
    //PowerManager.WakeLock wakeLock = mgr.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK |         PowerManager.ACQUIRE_CAUSES_WAKEUP, "MyWakeLock");


    sensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);
    accelerometer = sensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);
}

public void onStartClick(View view) {
    sensorManager.registerListener(this, accelerometer, SensorManager.SENSOR_DELAY_NORMAL);
    btnStop.setEnabled(true);
    btnStart.setEnabled(false);

}

public void onStopClick(View view) {
    sensorManager.unregisterListener(this);
    btnStart.setEnabled(true);
    btnStop.setEnabled(false);
}
protected void onResume() {
    super.onResume();
    try {
        writer = new FileWriter(root + "/acc2txt-file.txt",true);
    } catch (IOException e) {
        e.printStackTrace();
    }
}

protected void onPause() {
    super.onPause();
    if(writer != null) {
        try {
            writer.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}



@Override
public void onAccuracyChanged(Sensor sensor, int accuracy) {

}

@Override
public void onSensorChanged(SensorEvent event) {

    float x = event.values[0];
    float y = event.values[1];
    float z = event.values[2];
    SimpleDateFormat time = new SimpleDateFormat("HH:mm:ss:SSS");
    String s = time.format(new java.util.Date());
    try {
        writer.write(s+"\t"+x+"\t"+y+"\t"+z+"\n");
    } catch (IOException e) {
        e.printStackTrace();
    }

}

}

Answer 1

如果你想在app stop中保存数据，你可以用START_STICKY选项编写服务，那么即使应用被杀死，服务也会保持活动状态。以下是STICKY服务的示例，它非常简单，符合您的需求example 1 example 2

public class MyService extends Service {

protected String messageData = null;
public static final int MSG_REGISTER_CLIENT   = 1;
public static final int MSG_UNREGISTER_CLIENT = 2;
public static final int MSG_CUSTOM_TYPE       = 3;

@Override public void onCreate() {

    super.onCreate();

    MyServiceRunningBackground();


    running = true;

}



@Override public int onStartCommand(Intent intent, int flags, int startId) {

    return START_STICKY;
}

@Override
public IBinder onBind(Intent intent) {
    //TODO for communication return IBinder implementation
    return null;
}


@Override public boolean onUnbind(Intent intent) {

    return super.onUnbind(intent);
}

@Override public void onRebind(Intent intent) {

    super.onRebind(intent);
}

@Override public void onDestroy() {

    super.onDestroy();

    running = false;
}


private void MyServiceRunningBackground() {

    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT)
    {
        final int restartAlarmInterval = 6000;
        final int resetAlarmTimer = 2*1000;
        final Intent restartIntent = new Intent(this, esService.class);
        restartIntent.putExtra("ALARM_RESTART_SERVICE_DIED", true);
        final AlarmManager alarmMgr = (AlarmManager)getSystemService(Context.ALARM_SERVICE);
        Handler restartServiceHandler = new Handler()
        {
            @Override
            public void handleMessage(Message msg) {
                PendingIntent pintent = PendingIntent.getService(getApplicationContext(), 0, restartIntent, 0);
                alarmMgr.set(AlarmManager.ELAPSED_REALTIME, SystemClock.elapsedRealtime() + restartAlarmInterval, pintent);
                sendEmptyMessageDelayed(0, resetAlarmTimer);
            }
        };
        restartServiceHandler.sendEmptyMessageDelayed(0, 0);
    }
}




private static final String TAG = "MyService";

}

创建这项新服务并执行您希望在您的应用程序后台保存数据的情况下执行的工作，即使您的应用程序被杀，只需启动此服务，就像在onCreate of activity中打开新意图一样。之后，即使用户杀死应用程序，此服务也将处于活动状态。像这样开始这项服务

  Intent intent = new Intent(MyActivity.this, MyService.class);
    startService(intent);

我希望我很清楚

锁定屏幕后运行Android应用程序

1 个答案: