How to save a List from an Adapter to a xml File in Android?

Question

I have developed an app capable of detecting BLE signals and others parameters. I use a BaseAdapter to develop the ListView for showing each item. The problem is that I want to save those data in a xml file when the scan has finished (after a period of time I have established) but I don´t know how to do it.

In this class I do the scan of BLE and is where I want to initiate the process of saving the List when it has passed the time of scanning:

public class ScanBleActivity extends ScanBaseActivity {

private BluetoothAdapter mBluetoothAdapter;
private boolean mScanning;
private Handler mHandler = new Handler();
//private List<BluetoothDevice> mydata;

// Stops scanning after 10 seconds.
private static final long SCAN_PERIOD = 20000;

/* (non-Javadoc)
 * @see com.zishao.bletest.ScanBaseActivity#initScanBluetooth()
 */
protected void initScanBluetooth() {
    BluetoothManager manager = (BluetoothManager) getSystemService(Context.BLUETOOTH_SERVICE);
    mBluetoothAdapter = manager.getAdapter();
    startScanLen(true);
}

@Override
protected void onDestroy() {
    super.onDestroy();
    if (mScanning) {
        startScanLen(false);
    }
}

/**
 * 
 * @param enable
 */
private void startScanLen(final boolean enable) {
    if (enable) {
        // Stops scanning after a pre-defined scan period.
        mHandler.postDelayed(new Runnable() {
            @Override
            public void run() {
                mScanning = false;
                mBluetoothAdapter.stopLeScan(mLeScanCallback);
                try {
                    savedata(true);
                } catch (FileNotFoundException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }

            }
        }, SCAN_PERIOD);

        mScanning = true;
        mBluetoothAdapter.startLeScan(mLeScanCallback);
    } else {
        mScanning = false;
        mBluetoothAdapter.stopLeScan(mLeScanCallback);
    }
}

And here is my Adapter:

public class LeDeviceListAdapter extends BaseAdapter {
public List<BluetoothDevice> data;
private Activity context;
private final HashMap<BluetoothDevice, Integer> rssiMap = new HashMap<BluetoothDevice, Integer>();



public LeDeviceListAdapter(Activity context, List<BluetoothDevice> data) {
    this.data = data;
    this.context = context;

}
//public static List<BluetoothDevice> getAllData() {
//  return data;
//}

public synchronized void addDevice(BluetoothDevice device, int rssi) {
    if(!data.contains(device) ){
    data.add(device);
    }
    rssiMap.put(device, rssi);
}

@Override
public int getCount() {
    return data.size();
}

@Override
public Object getItem(int position) {
    return data.get(position);
}

@Override
public long getItemId(int position) {
    return position;
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    if (null == convertView) {
        LayoutInflater mInflater =
            (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        convertView = mInflater.inflate(R.layout.leaf_devices_list_item, null);
        convertView.setTag(new DeviceView(convertView));
    }
    DeviceView view = (DeviceView) convertView.getTag();
    view.init((BluetoothDevice) getItem(position));
    return convertView;
}

public class DeviceView {



    private TextView title;
    private TextView status;
    private TextView type;
    private TextView address;
    private TextView rssivalue;

    public DeviceView(View view) {
        title = (TextView) view.findViewById(R.id.device_name);
        status = (TextView) view.findViewById(R.id.device_status_txt);
        type = (TextView) view.findViewById(R.id.device_type_txt);
        address = (TextView) view.findViewById(R.id.device_address_txt);
        rssivalue = (TextView) view.findViewById(id.signal_intensity_txt);
    }

    public void init(BluetoothDevice device) {
        title.setText(device.getName());
        address.setText(device.getAddress());
        setType(device.getType());
        setStatus(device.getBondState());
        rssivalue.setText(""+rssiMap.get(device)+" dBm");

    }

    public void setType(int status) {
        switch(status) {
        case BluetoothDevice.DEVICE_TYPE_CLASSIC:
            type.setText("Bluetooth Signal");
            break;
        case BluetoothDevice.DEVICE_TYPE_LE:
            type.setText("BLE Signal");
            break;
        case BluetoothDevice.DEVICE_TYPE_DUAL:
            type.setText("Dual Mode - BR/EDR/LE");
            break;
        case BluetoothDevice.DEVICE_TYPE_UNKNOWN:
            type.setText("Device Unknown");
            break;
        }
    }

    public void setStatus(int s) {
        switch(s) {
        case BluetoothDevice.BOND_NONE:
            status.setText("Not Bonded");
            break;
        case BluetoothDevice.BOND_BONDED:
            status.setText("Bonded");
            break;
        case BluetoothDevice.BOND_BONDING:
            status.setText("Bonding");
            break;
        }
    }


}

I want to save the title, address, type, status and rssivalue (shown in the code above) of each BLE signal that has been found during the scan to be saved in a xml file. I have provided only a part of the project but if it is necessarly I will edit and put the code that is missing.

Does anyone know how to do it?? Please help!!!!!

New code: This corresponds to the class ScanBaseActivity:

abstract public class ScanBaseActivity extends ListActivity {

protected LeDeviceListAdapter mLeDeviceListAdapter;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_devices_scan);
    mLeDeviceListAdapter = new LeDeviceListAdapter(this, new ArrayList<BluetoothDevice>());
    this.setListAdapter(mLeDeviceListAdapter);
    initScanBluetooth();
}

/**
 * Start Scan Bluetooth
 * 
 */
abstract protected void initScanBluetooth();

@Override
protected void onListItemClick(ListView l, View v, int position, long id) {
    BluetoothDevice device = (BluetoothDevice) mLeDeviceListAdapter.getItem(position);
    ParcelUuid[] uuids = device.getUuids();
    String uuidString = "Getting UUID's from " + device.getName() + ";UUID:";
    if (null != uuids && uuids.length > 0) {
        uuidString += uuids[0].getUuid().toString();
    } else {
        uuidString += "empty";
    }
    Toast.makeText(this, uuidString, Toast.LENGTH_LONG).show();
}

/**
 * @param device
 */
protected synchronized void addDevice(final BluetoothDevice device, final int rssi) {
    runOnUiThread(new Runnable() {
        @Override
        public void run() {
            mLeDeviceListAdapter.addDevice(device, rssi);
            mLeDeviceListAdapter.notifyDataSetChanged();
        }
    });
}

protected void savedata(boolean enable) throws FileNotFoundException{

        String filename = "file.txt";

        FileOutputStream fos;
        Bundle extras = getIntent().getExtras();
        long timestamp = extras.getLong("currentTime");
        try {
        fos= openFileOutput(filename, Context.MODE_PRIVATE);
        ObjectOutputStream out = new ObjectOutputStream(fos);
        out.write((int) timestamp);
        out.writeObject(mLeDeviceListAdapter);
        out.write(null);
        out.close();
        Toast.makeText(this, R.string.list_saved, Toast.LENGTH_SHORT).show();
        savedata(false);
        } catch (FileNotFoundException e){
            e.printStackTrace();
        } catch (IOException e){
            e.printStackTrace();
        }

    }
}

New!!: I have edited ScanBaseActivity and ScanBleActivity to introduce the xml saving but when I run the app, when the scan stops it causes an error (moment when the list has to be saved in the sml file). Does anyone know how to solve it or correct it??!!!

Answer 1

Well, it's not that you are going to be saving it from the adapter, it's that the adater is going to be 'adapting' a data set that you will put into preferences.

as a feild:

private SharedPreferences saveHash;

in onCreate:

saveHash = getSharedPreferences( getString( R.string.save_hash ), MODE_PRIVATE );

then later:

public void onFinishedLoading(){
    super.onPause();
    SharedPreferences.Editor editor = saveHash.edit();
    editor.clear();
    for( String s: myData){
        editor.putString(x, s);
    }
    editor.commit();
}

edit: realized you want to make a hash from a list; what do you want as the key?

Answer 2

OK, first, you need to re-shape how you are dealing with your adapter, after that, everything should fall into place.

so for that, I'm going to outsource to vogella, the cardinal of good android design patterns http://www.vogella.com/tutorials/AndroidListView/article.html

you could read up through section 3, eat some copypasta and come back here, but every extra line you grok is a good thing =]

Now you have an activity that has a list of data, and an adapter that takes that list and--somewhat dumbly in comparison to your code--applies it to a view of some sort. When you want to update that data, you do so by modifying the List object in the activity by your method somewhere that gets a list of Bluetoothdevices--and I'd take that process off thread with an AsyncTask.

Since you are passing a List to the adapter, you can wait until you've populated the data in your activity, then do an adapter.notifyDataSetChanged. You do not want to adapter.add

then you have a nice List of your data in the activity; you don't need to worry if it's the right list, because--given the update pattern--it's the only list!

then follow the link Merleverde posted to serialize that data into an xml, maybe in a utility class, but in your activity is fine.

edit: here is a perfectly good adapter, this is part of the larger pattern that displays dynamically changing data:

public class AnchorListAdapter extends ArrayAdapter<String>
{

private final List<String> anchorNames;
public AnchorListAdapter(Context context, int textviewId, List<String> anchors){
    super(context, textviewId, anchors);
    anchorNames = anchors;
}

@Override
public String getItem( int i ) {
    return anchorNames.get(i).toString();
}

}