AccelerometerRecordToFileActivity.java

package com.google.mcommerce.sample.android.chapter08.sensor;

import java.io.BufferedWriter;
import java.io.FileWriter;
import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Date;

import android.app.Activity;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
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.os.PowerManager.WakeLock;
import android.provider.Settings;
import android.util.Log;

import com.google.mcommerce.sample.android.R;

public class AccelerometerRecordToFileActivity extends Activity implements
		SensorEventListener {
	private static final String TAG = "AccelerometerRecordToFile";
	private WakeLock mWakelock = null;
	private SensorManager mMgr;
	private Sensor mAccel;
	private BufferedWriter mLog;
	final private SimpleDateFormat mTimeFormat = new SimpleDateFormat(
			"HH:mm:ss - ");
	private int mSavedTimeout;

	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.c08_sensor_accelerometer_record_file);

		mMgr = (SensorManager) this.getSystemService(SENSOR_SERVICE);

		mAccel = mMgr.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);

		// Setup the log file to write to. We will append it just in case this
		// activity restarts in the middle of our experiment.
		try {
			String filename = Environment.getExternalStorageDirectory()
					.getAbsolutePath() + "/accel.log";
			mLog = new BufferedWriter(new FileWriter(filename, true));
		} catch (Exception e) {
			Log.e(TAG, "Unable to initialize the logfile");
			e.printStackTrace();
			finish();
		}

		PowerManager pwrMgr = (PowerManager) this
				.getSystemService(POWER_SERVICE);
		mWakelock = pwrMgr.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, "Accel");
		mWakelock.acquire();

		// Save the current value of the screen timeout, then set it to 5
		// seconds
		try {
			mSavedTimeout = Settings.System.getInt(getContentResolver(),
					Settings.System.SCREEN_OFF_TIMEOUT);
		} catch (Exception e) {
			mSavedTimeout = 120000; // 2 minutes
		}
		Settings.System.putInt(getContentResolver(),
				Settings.System.SCREEN_OFF_TIMEOUT, 5000); // 5 seconds
	}

	public BroadcastReceiver mReceiver = new BroadcastReceiver() {
		public void onReceive(Context context, Intent intent) {
			if (Intent.ACTION_SCREEN_OFF.equals(intent.getAction())) {
				writeLog("The screen has turned off");
				// Unregisters the listener and registers it again.

				mMgr.unregisterListener(AccelerometerRecordToFileActivity.this);
				mMgr.registerListener(AccelerometerRecordToFileActivity.this,
						mAccel, SensorManager.SENSOR_DELAY_NORMAL);

			}
		}
	};

	@Override
	protected void onStart() {
		writeLog("starting...");
		mMgr.registerListener(this, mAccel, SensorManager.SENSOR_DELAY_NORMAL);

		IntentFilter filter = new IntentFilter(Intent.ACTION_SCREEN_OFF);
		registerReceiver(mReceiver, filter);

		super.onStart();
	}

	@Override
	protected void onStop() {
		writeLog("stopping...");
		mMgr.unregisterListener(this, mAccel);
		unregisterReceiver(mReceiver);
		try {
			mLog.flush();
		} catch (IOException e) {
			// ignore any errors with the logfile
		}
		super.onStop();
	}

	@Override
	protected void onDestroy() {
		writeLog("shutting down...");
		try {
			mLog.flush();
			mLog.close();
		} catch (Exception e) {
			// ignore any errors with the logfile
		}

		// Restore the screen off timeout to the previous value
		Settings.System.putInt(getContentResolver(),
				Settings.System.SCREEN_OFF_TIMEOUT, mSavedTimeout);

		mWakelock.release();

		super.onDestroy();
	}

	public void onAccuracyChanged(Sensor sensor, int accuracy) {
		// ignore
	}

	public void onSensorChanged(SensorEvent event) {
		writeLog("Got a sensor event: " + event.values[0] + ", "
				+ event.values[1] + ", " + event.values[2]);
	}

	private void writeLog(String str) {
		try {
			Date now = new Date();
			mLog.write(mTimeFormat.format(now));
			mLog.write(str);
			mLog.write("\n");
		} catch (IOException ioe) {
			ioe.printStackTrace();
		}
	}
}