关于BluetoothAdapter扫描设备问题

[qq_25269561]

目前测试一个小功能，但是BluetoothAdapter.startDiscovery()总是扫描不出设备来，下面是代码，求大神帮忙看看。
public class MainActivity extends Activity {
BluetoothAdapter mAdapter;
BluetoothManager bluetoothManager;
Boolean isScan;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button click = (Button) findViewById(R.id.btnClick);
bluetoothManager = (BluetoothManager) this
.getSystemService(Context.BLUETOOTH_SERVICE);
mAdapter = bluetoothManager.getAdapter();
IntentFilter intentFilter = new IntentFilter();
intentFilter.addAction(BluetoothDevice.ACTION_FOUND);
registerReceiver(bre, intentFilter);

click.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
if (mAdapter != null && !mAdapter.isEnabled()) {
startActivityForResult(new Intent(
BluetoothAdapter.ACTION_REQUEST_ENABLE), 0);
}
}
});
}

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
// TODO Auto-generated method stub
super.onActivityResult(requestCode, resultCode, data);
if(resultCode==Activity.RESULT_OK){
if(mAdapter.isEnabled()){
isScan = mAdapter.startDiscovery();
Log.e("isScan", isScan+"");
}
}
}

@Override
protected void onDestroy() {
// TODO Auto-generated method stub
super.onDestroy();
// unregisterReceiver();
mAdapter.disable();
unregisterReceiver(bre);
}

public BroadcastReceiver bre = new BroadcastReceiver() {
public void onReceive(Context context, Intent intent) {
String action = intent.getAction();
if (BluetoothDevice.ACTION_FOUND.equals(action)) {
BluetoothDevice device = intent
.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
Log.e("INFO", device.getName()+"---"+device.getAddress());
}
};
};
}