空指针异常错误发送一个特征 BLE android
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【中文标题】空指针异常错误发送一个特征 BLE android【英文标题】：Null pointer exception error sending a characteristic BLE android 【发布时间】：2014-07-13 06:04:02 【问题描述】：我是一名新的 android 开发人员，我正在尝试使用 BLE 4.3 发送数据，基于 Gatt android 示例项目。
我使用特性来放置我想要传输的数据。
当我尝试传输时，我使用项目的DeviceControlActivity 列表中的第三个服务，出现一个文本对话框来介绍文本。当我按下 OK 时，想法是开始传输，但我得到一个NullPointerException 错误。
我不知道为什么会出现这个错误，我该如何解决这个问题。
这是我的完整代码，如果有用的话
package com.example.blem;
public class DeviceControlActivity extends Activity
public static final String EXTRAS_DEVICE_NAME = "DEVICE_NAME";
public static final String EXTRAS_DEVICE_ADDRESS = "DEVICE_ADDRESS";
private TextView mConnectionState;
private TextView mDataField;
private TextView mRssiField;
private String mDeviceName;
private String mDeviceAddress;
private ExpandableListView mGattServicesList;
private BluetoothLeService mBluetoothLeService;
private ArrayList<ArrayList<BluetoothGattCharacteristic>> mGattCharacteristics =
new ArrayList<ArrayList<BluetoothGattCharacteristic>>();
private boolean mConnected = false;
private BluetoothGattCharacteristic mNotifyCharacteristic;
private BluetoothGattCharacteristic mWriteCharacteristic;
Button Escritor;
byte hello []=0;
private final String LIST_NAME = "NAME";
private final String LIST_UUID = "UUID";
BluetoothGattCharacteristic characteristic;
public BluetoothGatt mBluetoothGatt;
// Code to manage Service lifecycle.
private final ServiceConnection mServiceConnection = new ServiceConnection()
@Override
public void onServiceConnected(ComponentName componentName, IBinder service)
mBluetoothLeService = ((BluetoothLeService.LocalBinder) service).getService();
if (!mBluetoothLeService.initialize())
Log.e("Unable to initialize Bluetooth");
finish();
// Automatically connects to the device upon successful start-up initialization.
mBluetoothLeService.connect(mDeviceAddress);
mBluetoothLeService.setBLEServiceCb(mDCServiceCb);
@Override
public void onServiceDisconnected(ComponentName componentName)
mBluetoothLeService = null;
;
// If a given GATT characteristic is selected, check for supported features. This sample
// demonstrates 'Read' and 'Notify' features. See
// http://d.android.com/reference/android/bluetooth/BluetoothGatt.html for the complete
// list of supported characteristic features.
private final ExpandableListView.OnChildClickListener servicesListClickListner =
new ExpandableListView.OnChildClickListener()
@TargetApi(Build.VERSION_CODES.JELLY_BEAN_MR2)
@Override
public boolean onChildClick(ExpandableListView parent, View v, int groupPosition,
int childPosition, long id)
if (mGattCharacteristics != null)
final BluetoothGattCharacteristic characteristic =
mGattCharacteristics.get(groupPosition).get(childPosition);
final int charaProp = characteristic.getProperties();
if ((charaProp & BluetoothGattCharacteristic.PROPERTY_READ) > 0)
// If there is an active notification on a characteristic, clear
// it first so it doesn't update the data field on the user interface.
Log.d("BluetoothGattCharacteristic has PROPERTY_READ, so send read request");
if (mNotifyCharacteristic != null)
mBluetoothLeService.setCharacteristicNotification(
mNotifyCharacteristic, false);
mNotifyCharacteristic = null;
mBluetoothLeService.readCharacteristic(characteristic);
if ((charaProp & BluetoothGattCharacteristic.PROPERTY_NOTIFY) > 0)
Log.d("BluetoothGattCharacteristic has PROPERTY_NOTIFY, so send notify request");
mNotifyCharacteristic = characteristic;
mBluetoothLeService.setCharacteristicNotification(
characteristic, true);
if (((charaProp & BluetoothGattCharacteristic.PROPERTY_WRITE) |
(charaProp & BluetoothGattCharacteristic.PROPERTY_WRITE_NO_RESPONSE)) > 0)
Log.d("BluetoothGattCharacteristic has PROPERY_WRITE | PROPERTY_WRITE_NO_RESPONSE");
mWriteCharacteristic = characteristic;
// popup an dialog to write something.
showCharactWriteDialog();
return true;
return false;
;
private void showCharactWriteDialog()
DialogFragment newFrame = new BleCharacterDialogFragment();
newFrame.show(getFragmentManager(), "blewrite");
private void clearUI()
mGattServicesList.setAdapter((SimpleExpandableListAdapter) null);
mDataField.setText(R.string.no_data);
@TargetApi(Build.VERSION_CODES.HONEYCOMB)
@Override
public void onCreate(Bundle savedInstanceState)
super.onCreate(savedInstanceState);
setContentView(R.layout.gatt_services_characteristics);
final Intent intent = getIntent();
mDeviceName = intent.getStringExtra(EXTRAS_DEVICE_NAME);
mDeviceAddress = intent.getStringExtra(EXTRAS_DEVICE_ADDRESS);
// Sets up UI references.
((TextView) findViewById(R.id.device_address)).setText(mDeviceAddress);
mGattServicesList = (ExpandableListView) findViewById(R.id.gatt_services_list);
mGattServicesList.setOnChildClickListener(servicesListClickListner);
mConnectionState = (TextView) findViewById(R.id.connection_state);
mDataField = (TextView) findViewById(R.id.data_value);
mRssiField = (TextView) findViewById(R.id.signal_rssi);
//Escritor = (Button) findViewById(R.id.escrito);
/*Escritor.setOnClickListener(new View.OnClickListener()
@Override
public void onClick(View v)
characteristic.setValue(new byte[] (byte) 0xFF);
writeCharacteristicValue(characteristic);
Toast.makeText(getApplicationContext(), "Se envío el dato",
Toast.LENGTH_SHORT).show();
return;
);*/
getActionBar().setTitle(mDeviceName);
getActionBar().setDisplayHomeAsUpEnabled(true);
Intent gattServiceIntent = new Intent(this, BluetoothLeService.class);
bindService(gattServiceIntent, mServiceConnection, BIND_AUTO_CREATE);
@Override
protected void onResume()
super.onResume();
//registerReceiver(mGattUpdateReceiver, makeGattUpdateIntentFilter());
if (mBluetoothLeService != null)
final boolean result = mBluetoothLeService.connect(mDeviceAddress);
Log.d("Connect request result=" + result);
@Override
protected void onPause()
super.onPause();
//unregisterReceiver(mGattUpdateReceiver);
@Override
protected void onDestroy()
super.onDestroy();
unbindService(mServiceConnection);
mBluetoothLeService = null;
@Override
public boolean onCreateOptionsMenu(Menu menu)
getMenuInflater().inflate(R.menu.gatt_services, menu);
if (mConnected)
menu.findItem(R.id.menu_connect).setVisible(false);
menu.findItem(R.id.menu_disconnect).setVisible(true);
else
menu.findItem(R.id.menu_connect).setVisible(true);
menu.findItem(R.id.menu_disconnect).setVisible(false);
return true;
@TargetApi(Build.VERSION_CODES.ECLAIR)
@Override
public boolean onOptionsItemSelected(MenuItem item)
switch(item.getItemId())
case R.id.menu_connect:
mBluetoothLeService.connect(mDeviceAddress);
return true;
case R.id.menu_disconnect:
mBluetoothLeService.disconnect();
return true;
case android.R.id.home:
onBackPressed();
return true;
return super.onOptionsItemSelected(item);
private void updateConnectionState(final int resourceId)
runOnUiThread(new Runnable()
@Override
public void run()
mConnectionState.setText(resourceId);
);
private void displayData(String data)
if (data != null)
mDataField.setText(data);
private void displayRssi(String rssi)
if (rssi != null)
//Log.d("-- dispaly Rssi: " + rssi);
mRssiField.setText(rssi);
// Demonstrates how to iterate through the supported GATT Services/Characteristics.
// In this sample, we populate the data structure that is bound to the ExpandableListView
// on the UI.
@TargetApi(Build.VERSION_CODES.JELLY_BEAN_MR2)
private void displayGattServices(List<BluetoothGattService> gattServices)
Log.d("displayGATTServices");
if (gattServices == null) return;
String uuid = null;
String unknownServiceString = getResources().getString(R.string.unknown_service);
String unknownCharaString = getResources().getString(R.string.unknown_characteristic);
ArrayList<HashMap<String, String>> gattServiceData = new ArrayList<HashMap<String, String>>();
ArrayList<ArrayList<HashMap<String, String>>> gattCharacteristicData
= new ArrayList<ArrayList<HashMap<String, String>>>();
mGattCharacteristics = new ArrayList<ArrayList<BluetoothGattCharacteristic>>();
// Loops through available GATT Services.
for (BluetoothGattService gattService : gattServices)
HashMap<String, String> currentServiceData = new HashMap<String, String>();
uuid = gattService.getUuid().toString();
currentServiceData.put(
LIST_NAME, SampleGattAttributes.lookup(uuid, unknownServiceString));
currentServiceData.put(LIST_UUID, uuid);
gattServiceData.add(currentServiceData);
ArrayList<HashMap<String, String>> gattCharacteristicGroupData =
new ArrayList<HashMap<String, String>>();
List<BluetoothGattCharacteristic> gattCharacteristics =
gattService.getCharacteristics();
ArrayList<BluetoothGattCharacteristic> charas =
new ArrayList<BluetoothGattCharacteristic>();
// Loops through available Characteristics.
for (BluetoothGattCharacteristic gattCharacteristic : gattCharacteristics)
charas.add(gattCharacteristic);
HashMap<String, String> currentCharaData = new HashMap<String, String>();
uuid = gattCharacteristic.getUuid().toString();
currentCharaData.put(
LIST_NAME, SampleGattAttributes.lookup(uuid, unknownCharaString));
currentCharaData.put(LIST_UUID, uuid);
gattCharacteristicGroupData.add(currentCharaData);
mGattCharacteristics.add(charas);
gattCharacteristicData.add(gattCharacteristicGroupData);
SimpleExpandableListAdapter gattServiceAdapter = new SimpleExpandableListAdapter(
this,
gattServiceData,
android.R.layout.simple_expandable_list_item_2,
new String[] LIST_NAME, LIST_UUID,
new int[] android.R.id.text1, android.R.id.text2 ,
gattCharacteristicData,
android.R.layout.simple_expandable_list_item_2,
new String[] LIST_NAME, LIST_UUID,
new int[] android.R.id.text1, android.R.id.text2
);
mGattServicesList.setAdapter(gattServiceAdapter);
private DCServiceCb mDCServiceCb = new DCServiceCb();
public class DCServiceCb implements BluetoothLeService.BLEServiceCallback
@Override
public void displayRssi(final int rssi)
runOnUiThread(new Runnable()
@Override
public void run()
DeviceControlActivity.this.displayRssi(String.valueOf(rssi));
);
@Override
public void displayData(final String data)
runOnUiThread(new Runnable()
@Override
public void run()
DeviceControlActivity.this.displayData(data);
);
@Override
public void notifyConnectedGATT()
runOnUiThread(new Runnable()
@Override
public void run()
mConnected = true;
updateConnectionState(R.string.connected);
invalidateOptionsMenu();
);
@Override
public void notifyDisconnectedGATT()
runOnUiThread(new Runnable()
@Override
public void run()
mConnected = false;
updateConnectionState(R.string.disconnected);
invalidateOptionsMenu();
clearUI();
);
@Override
public void displayGATTServices()
Log.d("displayGATTServices.");
runOnUiThread(new Runnable()
@Override
public void run()
if (mBluetoothLeService != null)
DeviceControlActivity.this.displayGattServices(
mBluetoothLeService.getSupportedGattServices());
);
@SuppressLint("ValidFragment")
public class BleCharacterDialogFragment extends DialogFragment
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState)
View v = inflater.inflate(R.layout.write_charact_dialog, container, false);
final EditText ed = (EditText) v.findViewById(R.id.charact_value);
Button ok = (Button) v.findViewById(R.id.dialog_confirm);
Button cancel = (Button) v.findViewById(R.id.dialog_cancel);
ok.setOnClickListener(new View.OnClickListener()
@Override
public void onClick(View v)
characteristic.setValue(hello);
//characteristic.setValue("FF");
//characteristic.setValue(new byte[] (byte) 0xFF);
writeCharacteristicValue(characteristic);
Toast.makeText(getApplicationContext(), "Se envío el dato",
Toast.LENGTH_SHORT).show();
dismiss();
return;
);
cancel.setOnClickListener(new View.OnClickListener()
@Override
public void onClick(View v)
dismiss();
);
return v;
public void writeCharacteristicValue(BluetoothGattCharacteristic characteristica)
byte[] value= (byte) 0xFF;
characteristica.setValue(bytesToHex(value));
boolean status = mBluetoothGatt.writeCharacteristic(characteristica);
final protected static char[] hexArray = "0123456789ABCDEF".toCharArray();
public String bytesToHex(byte[] bytes)
char[] hexChars = new char[bytes.length * 2];
int v;
for ( int j = 0; j < bytes.length; j++ )
v = bytes[j] & 0xFF;
hexChars[j * 2] = hexArray[v >>> 4];
hexChars[j * 2 + 1] = hexArray[v & 0x0F];
return new String(hexChars);
谁能告诉我我做错了什么？
感谢提前
【问题讨论】：
查看堆栈跟踪并查看由部分引起的。 【参考方案1】：没有堆栈跟踪，这是不可能真正调试的，但从外观上看，您并没有使用 onServicesDiscovered() 和 onCharacteristicRead() 回调来等待读取所有服务和相应的特征，因此您没有了解这些事件何时发生并因此能够继续
【讨论】：
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