问一下本人在蓝牙ble调试的时候，搜索蓝牙设备的时候报这个错：
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.mybleyyy/com.example.mybleyyy.ControlActivity}: java.lang.NullPointerException: Attempt to invoke virtual method “boolean android.bluetooth.BluetoothAdapter.startLeScan(android.bluetooth.BluetoothAdapter$LeScanCallback)” on a null object reference
是哪里出问题了？

private void scanLeDevice(final boolean enable) {
        if (enable) {
            // Stops scanning after a pre-defined scan period.
            mHandler.postDelayed(new Runnable() {
                @Override
                public void run() {
                    mScanning = false;
                    adapter.stopLeScan(mLeScanCallback);
                    invalidateOptionsMenu();
                }
            }, 10000);
            mScanning = true;
            adapter.startLeScan(mLeScanCallback); //mScanning = false;
            //adapter.stopLeScan(mLeScanCallback);
            //System.err.println("*************停止BLE扫描*************");
            for(BluetoothDevice btd : bluetoothDevicesSet){
                HashMap<String, String> mapName = new HashMap<String, String>();
                mapName.put("ItemTitle", btd.getName()+"/address:"+btd.getAddress());
                System.err.println("*************ItemTitle*************"+btd.getName());
                mylist.add(mapName);
                bluetoothDevicesList.add(btd);
                simpleAdapter = new SimpleAdapter(getApplicationContext(), mylist, R.layout.bt_device_list, new String[] {"ItemTitle"}, new int[] {R.id.device_name});
                //加载SimpleAdapter到ListView中
                listview_newDevices.setAdapter(simpleAdapter);
            }} else {
            mScanning = false;
            adapter.stopLeScan(mLeScanCallback);
        }
        invalidateOptionsMenu();
    }

private BluetoothAdapter.LeScanCallback mLeScanCallback = new BluetoothAdapter.LeScanCallback() {
        @Override
        public void onLeScan(final BluetoothDevice device, int rssi, byte[] scanRecord) {
            runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    System.err.println("onLeScan:"+device.getAddress()+"*******"+device.getName()+"*******");
                    Toast.makeText(ControlActivity.this, "onLeScan:"+device.getAddress()+"*******"+device.getName()+"*******", Toast.LENGTH_SHORT).show();
                    bluetoothDevicesSet.add(device);
                }
            });
        }
    };