锁定屏幕后运行的Android应用程序

Question

您好，我是android编程新手。我正在为学校编写一个应用程序，我需要将加速度计数据保存到一个txt文件中。 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？

这里是我的代码：

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

，如果你想保存在应用程序数据也都会停止，你可以写与START_STICKY选项服务，则服务保持活动状态，即使应用程序被杀害。下面是例子粘滞服务的，它很容易，并会满足您的需求example 1example 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"; 

}

创建这个新业务，做你想要在你的情况下在后台将数据保存到执行什么工作，你的应用程序，即使你的应用程序被杀害，只要启动这项服务，就像在你的onCreate活动中打开新的意图一样。之后，即使用户杀死应用程序，此服务也将处于活动状态。像这样开头

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

我希望我清楚