我正在尝试编写一个利用BLE功能的Android应用程序。我能够扫描并找到我要查找的设备但是，当我尝试连接到其中一个设备时，我收到以下错误：
02-22 18:28:54.603: I/ViewRootImpl(4155): ViewRoot's Touch Event : Touch Down
02-22 18:28:54.663: D/AndroidRuntime(4155): Shutting down VM
02-22 18:28:54.663: W/dalvikvm(4155): threadid=1: thread exiting with uncaught exception (group=0x41726e48)
02-22 18:28:54.663: I/ViewRootImpl(4155): ViewRoot's Touch Event : Touch UP
02-22 18:28:54.663: E/AndroidRuntime(4155): FATAL EXCEPTION: main
02-22 18:28:54.663: E/AndroidRuntime(4155): Process: com.example.ble_test, PID: 4155
02-22 18:28:54.663: E/AndroidRuntime(4155): java.lang.NullPointerException
02-22 18:28:54.663: E/AndroidRuntime(4155): at com.example.ble_test.DeviceControlActivity.onOptionsItemSelected(DeviceControlActivity.java:217)
02-22 18:28:54.663: E/AndroidRuntime(4155): at android.app.Activity.onMenuItemSelected(Activity.java:2644)
02-22 18:28:54.663: E/AndroidRuntime(4155): at com.android.internal.policy.impl.PhoneWindow.onMenuItemSelected(PhoneWindow.java:1096)
02-22 18:28:54.663: E/AndroidRuntime(4155): at com.android.internal.view.menu.MenuBuilder.dispatchMenuItemSelected(MenuBuilder.java:744)
02-22 18:28:54.663: E/AndroidRuntime(4155): at com.android.internal.view.menu.MenuItemImpl.invoke(MenuItemImpl.java:152)
02-22 18:28:54.663: E/AndroidRuntime(4155): at com.android.internal.view.menu.MenuBuilder.performItemAction(MenuBuilder.java:883)
02-22 18:28:54.663: E/AndroidRuntime(4155): at com.android.internal.view.menu.ActionMenuView.invokeItem(ActionMenuView.java:546)
02-22 18:28:54.663: E/AndroidRuntime(4155): at com.android.internal.view.menu.ActionMenuItemView.onClick(ActionMenuItemView.java:118)
02-22 18:28:54.663: E/AndroidRuntime(4155): at android.view.View.performClick(View.java:4442)
02-22 18:28:54.663: E/AndroidRuntime(4155): at android.view.View$PerformClick.run(View.java:18471)
02-22 18:28:54.663: E/AndroidRuntime(4155): at android.os.Handler.handleCallback(Handler.java:733)
02-22 18:28:54.663: E/AndroidRuntime(4155): at android.os.Handler.dispatchMessage(Handler.java:95)
02-22 18:28:54.663: E/AndroidRuntime(4155): at android.os.Looper.loop(Looper.java:136)
02-22 18:28:54.663: E/AndroidRuntime(4155): at android.app.ActivityThread.main(ActivityThread.java:5103)
02-22 18:28:54.663: E/AndroidRuntime(4155): at java.lang.reflect.Method.invokeNative(Native Method)
02-22 18:28:54.663: E/AndroidRuntime(4155): at java.lang.reflect.Method.invoke(Method.java:515)
02-22 18:28:54.663: E/AndroidRuntime(4155): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:790)
02-22 18:28:54.663: E/AndroidRuntime(4155): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:606)
02-22 18:28:54.663: E/AndroidRuntime(4155): at dalvik.system.NativeStart.main(Native Method)
02-22 18:33:54.696: I/Process(4155): Sending signal. PID: 4155 SIG: 9
02-22 18:33:55.326: D/ActivityThread(4235): setTargetHeapUtilization:0.25
点击“连接”后，应用程序因错误而关闭。这是我的DeviceControlActivity代码：
package com.example.ble_test;
import android.app.Activity;
import android.bluetooth.BluetoothGattCharacteristic;
import android.bluetooth.BluetoothGattService;
import android.content.BroadcastReceiver;
import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.content.ServiceConnection;
import android.os.Bundle;
import android.os.IBinder;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.ExpandableListView;
import android.widget.SimpleExpandableListAdapter;
import android.widget.TextView;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
/**
* For a given BLE device, this Activity provides the user interface to connect, display data,
* and display GATT services and characteristics supported by the device. The Activity
* communicates with {@code BluetoothLeService}, which in turn interacts with the
* Bluetooth LE API.
*/
public class DeviceControlActivity extends Activity {
private final static String TAG = DeviceControlActivity.class.getSimpleName();
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 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 final String LIST_NAME = "NAME";
private final String LIST_UUID = "UUID";
// 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(TAG, "Unable to initialize Bluetooth");
finish();
}
// Automatically connects to the device upon successful start-up initialization.
mBluetoothLeService.connect(mDeviceAddress);
}
@Override
public void onServiceDisconnected(ComponentName componentName) {
mBluetoothLeService = null;
}
};
// Handles various events fired by the Service.
// ACTION_GATT_CONNECTED: connected to a GATT server.
// ACTION_GATT_DISCONNECTED: disconnected from a GATT server.
// ACTION_GATT_SERVICES_DISCOVERED: discovered GATT services.
// ACTION_DATA_AVAILABLE: received data from the device. This can be a result of read
// or notification operations.
private final BroadcastReceiver mGattUpdateReceiver = new BroadcastReceiver() {
@Override
public void onReceive(Context context, Intent intent) {
final String action = intent.getAction();
if (BluetoothLeService.ACTION_GATT_CONNECTED.equals(action)) {
mConnected = true;
updateConnectionState(R.string.connected);
invalidateOptionsMenu();
} else if (BluetoothLeService.ACTION_GATT_DISCONNECTED.equals(action)) {
mConnected = false;
updateConnectionState(R.string.disconnected);
invalidateOptionsMenu();
clearUI();
} else if (BluetoothLeService.ACTION_GATT_SERVICES_DISCOVERED.equals(action)) {
// Show all the supported services and characteristics on the user interface.
displayGattServices(mBluetoothLeService.getSupportedGattServices());
} else if (BluetoothLeService.ACTION_DATA_AVAILABLE.equals(action)) {
displayData(intent.getStringExtra(BluetoothLeService.EXTRA_DATA));
}
}
};
// 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() {
@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.
if (mNotifyCharacteristic != null) {
mBluetoothLeService.setCharacteristicNotification(
mNotifyCharacteristic, false);
mNotifyCharacteristic = null;
}
mBluetoothLeService.readCharacteristic(characteristic);
}
if ((charaProp | BluetoothGattCharacteristic.PROPERTY_NOTIFY) > 0) {
mNotifyCharacteristic = characteristic;
mBluetoothLeService.setCharacteristicNotification(
characteristic, true);
}
return true;
}
return false;
}
};
private void clearUI() {
mGattServicesList.setAdapter((SimpleExpandableListAdapter) null);
mDataField.setText(R.string.no_data);
}
@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);
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(TAG, "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;
}
@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);
}
}
// 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.
private void displayGattServices(List<BluetoothGattService> gattServices) {
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 static IntentFilter makeGattUpdateIntentFilter() {
final IntentFilter intentFilter = new IntentFilter();
intentFilter.addAction(BluetoothLeService.ACTION_GATT_CONNECTED);
intentFilter.addAction(BluetoothLeService.ACTION_GATT_DISCONNECTED);
intentFilter.addAction(BluetoothLeService.ACTION_GATT_SERVICES_DISCOVERED);
intentFilter.addAction(BluetoothLeService.ACTION_DATA_AVAILABLE);
return intentFilter;
}
}
这也是我正在使用的菜单文件：
<?xml version="1.0" encoding="utf-8"?>
<!-- Copyright (C) 2013 The Android Open Source Project
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
-->
<menu xmlns:android="http://schemas.android.com/apk/res/android">
<item android:id="@+id/menu_refresh"
android:title="@string/menu_refresh"
android:checkable="false"
android:orderInCategory="1"
android:showAsAction="ifRoom"/>
<item android:id="@+id/menu_connect"
android:title="@string/menu_connect"
android:orderInCategory="100"
android:showAsAction="ifRoom|withText"/>
<item android:id="@+id/menu_disconnect"
android:title="@string/menu_disconnect"
android:orderInCategory="101"
android:showAsAction="ifRoom|withText"/>
</menu>
我之前能够超越这一点，但我不确定这次是什么问题。这一定是我忽略的事情。我正在尝试连接的设备是Bluegiga BLE113分线板。我们将非常感谢您提供的任何帮助！
答案 0 :(得分：0)
所以这是我遇到的错误的解决方案。以前，Manifest文件中的BluetoothLeService引用是：
<service
android:name="com.example.ble.BluetoothLeService"
android:enabled="true" />
但这是在另一个项目中的引用。一旦我改为：
<service
android:name="com.example.ble_test2.BluetoothLeService"
android:enabled="true" />
问题已得到纠正。
答案 1 :(得分：0)
我从之前的评论中看到，您已经知道它是一个空指针异常。简短的回答是在调用setText（）方法之前检查mConnectionState是否为null。像这样：
public void run() {
if (mConnectionState != null) {
mConnectionState.setText(resourceId);
}
}
我认为发生的事情是因为BroadcastReceiver异步触发，它会在第141行调用super.onCreate()的位置与您将mConnection()设置为TextView的位置之间触发第152行的实际boolean hasNativeFrag = false;
@Override
public boolean onOptionsItemSelected(MenuItem item) {
int id = item.getItemId();
if (id == R.id.native_chat) {
FragmentManager fragmentManager = getFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
NativeFragment nativeFragment = new NativeFragment();
//Add/remove fragment
if (!hasNativeFrag) {
getFragmentManager().executePendingTransactions();
fragmentTransaction.add(R.id.FragmentContainer, nativeFragment);
hasNativeFrag = true;
}
if(nativeFragment.isVisible()){
fragmentTransaction.hide(nativeFragment);
}
else {
fragmentTransaction.show(nativeFragment);
}
fragmentTransaction.commit();
}
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
。