空指针异常错误发送特征BLE的Android [英] Null pointer exception error sending a characteristic BLE android
本文介绍了空指针异常错误发送特征BLE的Android的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
我是一个新的Android开发人员，我想用来发送数据 BLE 4.3 ，基于Android的关贸总协定样本项目。
I'm a new android developer and I'm trying to send a data using BLE 4.3, based on Gatt android sample project.
我用的特性把，我想传输数据。
I use characteristics to put the data that i want to transmit.
当我尝试发射，我用的是第三个服务 DeviceControlActivity 项目列表中，会出现一个对话框文字介绍文字。当我preSS OK，这个想法是，开始发送，但我获得 NullPointerException异常错误。
When I try to transmit, I use the third service in the list of DeviceControlActivity of the project, appears a text dialog to introduce text. When I press OK, the idea is that start the transmission, but I obtain a NullPointerException error.
我不知道为什么会出现这个错误，我怎么能解决这个问题。
I don't know why appears this error and how can I solve this.
这是我的全code，如果这是非常有用的。
This is my full code, if this is useful
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);
}
}
的谁能告诉我什么，我做错了吗？的
感谢您提前
推荐答案
如果没有堆栈跟踪，这是不可能真正的调试，但是从它的外观，你没有使用 onServicesDiscovered（）和 onCharacteristicRead（）回调来等待所有的服务和各自的特点进行阅读，所以你有当这些事件发生的不知道，因此能继续
Without the stack trace this is impossible to truly debug, but from the looks of it you aren't using the onServicesDiscovered() and onCharacteristicRead() callbacks to wait for all the service and respective characteristics to be read so you have no idea when these events are occurring and thus are able to continue
这篇关于空指针异常错误发送特征BLE的Android的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
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