Scan for ble module (bluetooth 4.0) in android studio

Question

I'm trying to develop an app to scan for a BLE device. However, it only scans one time. I tried to use a while loop to loop it but it hangs there. The scanning part is at the proceed function:

package com.example.user.myfriend;

import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.bluetooth.BluetoothManager;
import android.content.Context;
import android.content.Intent;
import android.graphics.Color;
import android.os.Handler;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.RelativeLayout;
import android.widget.TextView;
import android.widget.Toast;

import org.w3c.dom.Text;


public class MainActivity extends ActionBarActivity {
BluetoothAdapter mBluetoothAdapter;

@Override
protected void onCreate(Bundle savedInstanceState) {


    BluetoothManager bluetoothManager = (BluetoothManager) getSystemService(Context.BLUETOOTH_SERVICE);
    mBluetoothAdapter = bluetoothManager.getAdapter();

    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    hello();

}

public void hello() {

    if (mBluetoothAdapter == null || !mBluetoothAdapter.isEnabled()) {
        Intent enableBluetooth = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);

        startActivityForResult(enableBluetooth, 1);


    }
    proceed();
}


@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {

    if (requestCode == 1) {
        if (resultCode == RESULT_OK) {
            proceed();


        }

    }
    super.onActivityResult(requestCode, resultCode, data);
}

private BluetoothAdapter.LeScanCallback mLeScanCallback = new BluetoothAdapter.LeScanCallback() {


    public void onLeScan(final BluetoothDevice device, final int rssi, final byte[] scanRecord) {

        int startByte = 2;
        boolean patternFound = false;
        while (startByte <= 5) {

            if (((int) scanRecord[startByte + 2] & 0xff) == 0x02 && //Identifies an iBeacon
                    ((int) scanRecord[startByte + 3] & 0xff) == 0x15) { //Identifies correct data length
                patternFound = true;
                break;
            }
            startByte++;
        }

        if (patternFound) {

            //Convert to hex String
            byte[] uuidBytes = new byte[16];
            System.arraycopy(scanRecord, startByte + 4, uuidBytes, 0, 16);
            String hexString = bytesToHex(uuidBytes);

            //Here is your UUID
            String uuid = hexString.substring(0, 8) + "-" +
                    hexString.substring(8, 12) + "-" +
                    hexString.substring(12, 16) + "-" +
                    hexString.substring(16, 20) + "-" +
                    hexString.substring(20, 32);

            //Here is your Major value
            int major = (scanRecord[startByte + 20] & 0xff) * 0x100 + (scanRecord[startByte + 21] & 0xff);

            //Here is your Minor value
            int minor = (scanRecord[startByte + 22] & 0xff) * 0x100 + (scanRecord[startByte + 23] & 0xff);

            if (major == 1) {
                RelativeLayout hai = (RelativeLayout) findViewById(R.id.hai);
                hai.setBackgroundColor(Color.YELLOW);

            }
            if (major == 2) {
                RelativeLayout hai = (RelativeLayout) findViewById(R.id.hai);
                hai.setBackgroundColor(Color.RED);

            }


        }


    }


};


private static String bytesToHex(byte[] bytes) {
    final char[] hexArray = "0123456789ABCDEF".toCharArray();
    char[] hexChars = new char[bytes.length * 2];
    for (int j = 0; j < bytes.length; j++) {
        int v = bytes[j] & 0xFF;
        hexChars[j * 2] = hexArray[v >>> 4];
        hexChars[j * 2 + 1] = hexArray[v & 0x0F];
    }
    return new String(hexChars);
}

public void proceed() {
    boolean scanning = true;

    mBluetoothAdapter.startLeScan(mLeScanCallback);


    Handler handler = new Handler();
    handler.postDelayed(new Runnable() {
        //  @Override
        public void run() {
            mBluetoothAdapter.stopLeScan(mLeScanCallback);


        }
    }, 50000000);

}

}

How can I make the app scan in a loop?

Answer 1

If "by scan in a loop?" you mean detect all nearby broadcasting devices, you have done it. The line of code:

mBluetoothAdapter.startLeScan(mLeScanCallback) 

causes scanning to begin. During scanning, the callback "mLeScanCallback" will be called as each broadcasting device is discovered. The scan will remain in effect until

mBluetoothAdapter.stopScan(mLeScanCallback) 

is called. In your case, this will get called after a very long time: 50000000 milliseconds.

Perhaps you only have 1 broadcasting device in the area so you only get 1 callback when you test.