Aripuca Tracker

First step in restoring database is selecting the actual file.

	private void restoreDatabase() {

		// show "select a file" dialog
		File importFolder = new File(myApp.getAppDir() + "/backup/");
		final String importFiles[] = importFolder.list();

		if (importFiles == null ||
				importFiles.length == 0) {
			Toast.makeText(MainActivity.this, R.string.source_folder_empty, Toast.LENGTH_SHORT).show();
			return;
		}

		importDatabaseFileName = importFiles[0];

		AlertDialog.Builder builder = new AlertDialog.Builder(this);
		builder.setTitle(R.string.select_file);
		builder.setSingleChoiceItems(importFiles, 0, new
				DialogInterface.OnClickListener() {
					public void onClick(DialogInterface dialog, int whichButton) {

						importDatabaseFileName = importFiles[whichButton];
						mainHandler.post(restoreDatabaseRunnable);

						dialog.dismiss();

					}
				});

		AlertDialog alert = builder.create();
		alert.show();

	}

Since we don’t know how much time the restoration process will take we do this in Runnable.

private Runnable restoreDatabaseRunnable = new Runnable() {
		@Override
		public void run() {

			try {

				// open database in readonly mode
				SQLiteDatabase db = SQLiteDatabase.openDatabase(
						myApp.getAppDir() + "/backup/" + importDatabaseFileName,
						null, SQLiteDatabase.OPEN_READONLY);

				// check version compatibility
				// only same version of the db can be restored
				if (myApp.getDatabase().getVersion() != db.getVersion()) {
					Toast.makeText(MainActivity.this, getString(R.string.restore_db_version_conflict),
							Toast.LENGTH_LONG).show();
					return;
				}

				db.close();

			} catch (SQLiteException e) {

				Toast.makeText(MainActivity.this, getString(R.string.restore_file_error) + ": " + e.getMessage(),
						Toast.LENGTH_LONG).show();

				return;
			}

			// closing current db
			myApp.getDatabase().close();

			try {

				File data = Environment.getDataDirectory();

				if (myApp.getExternalStorageWriteable()) {

					String restoreDBPath = myApp.getAppDir() + "/backup/" + importDatabaseFileName;

					File restoreDB = new File(restoreDBPath);
					File currentDB = new File(data, "/data/com.aripuca.tracker/databases/AripucaTracker.db");

					FileChannel src = new FileInputStream(restoreDB).getChannel();
					FileChannel dst = new FileOutputStream(currentDB).getChannel();

					dst.transferFrom(src, 0, src.size());
					src.close();
					dst.close();

					myApp.setDatabase();

				}

			}
			catch (Exception e) {

				Log.e(Constants.TAG, e.getMessage());

				myApp.setDatabase();

			}

		}
	};

Here is an example how to backup application database to external storage:

			File data = Environment.getDataDirectory();

			if (myApp.getExternalStorageWriteable()) {

				String currentDBPath = "/data/com.aripuca.tracker/databases/" + Constants.APP_NAME + ".db";

				String dateStr = (new SimpleDateFormat("yyyyMMdd_HHmmss")).format(new Date());

				File currentDB = new File(data, currentDBPath);
				File backupDB = new File(myApp.getAppDir() + "/backup/" + dateStr + ".db");

				if (currentDB.exists()) {
					FileChannel src = new FileInputStream(currentDB).getChannel();
					FileChannel dst = new FileOutputStream(backupDB).getChannel();
					dst.transferFrom(src, 0, src.size());
					src.close();
					dst.close();
				} else {
				}

			}

In next post I will publish working example of how to restore database from external storage and replace internal application db.

Implemented dedicated compass activity. Can display True and Magnetic North simultaneously (Magnetic North is semi-transparent).

The activity registers broadcast receiver and listens to updates from GPS service.

Compass Activity onResume method

public void onResume() {

	// registering receiver for compass updates
	IntentFilter filter = new IntentFilter("com.aripuca.tracker.COMPASS_UPDATES_ACTION");
	registerReceiver(compassBroadcastReceiver, filter);

	super.onResume();

}

Broadcast receiver declaration:

protected BroadcastReceiver compassBroadcastReceiver = new BroadcastReceiver() {
	@Override
	public void onReceive(Context context, Intent intent) {
		Bundle bundle = intent.getExtras();
		updateCompass(bundle.getFloat("azimuth"));
	}
};

Sending broadcast intent from GpsService

public void onSensorChanged(SensorEvent event) {

	// let's broadcast compass data to any activity waiting for updates
	Intent intent = new Intent("com.aripuca.tracker.COMPASS_UPDATES_ACTION");

	// packing azimuth value into bundle
	Bundle bundle = new Bundle();
	bundle.putFloat("azimuth", event.values[0]);

	intent.putExtras(bundle);			

	// broadcasting compass updates
	sendBroadcast(intent);

}

For complete working example see project source code.

Here is a simple function converting time interval in milliseconds to 0:00:00 format. It’s a good example of using StringBuilder class too.

public static String formatInterval(long milliseconds, boolean showHours) {

	int seconds = Math.round(milliseconds/1000.0f);

	int hours = (int) (seconds / 3600);
	int minutes = (int) (seconds / 60);
	if (minutes >= 60) {
		minutes = (int) (minutes % 60);
	}
	seconds = (int) (seconds % 60);

	StringBuilder builder = new StringBuilder();

	if (hours > 0 || showHours) {
		builder.append(hours);
		builder.append(":");
	}

	if (minutes <= 9) {
		builder.append("0");
	}
	builder.append(minutes);

	builder.append(":");

	if (seconds <= 9) {
		builder.append("0");
	}
	builder.append(seconds);

	return builder.toString();

}