Android致命异常：Main

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正在查找的设备，但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

一旦我点击connect，应用程序就会因为错误而关闭。以下是我的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;
}

}

下面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>

---

我以前能够超越这一点，但我不确定这次的问题是什么。一定是我忽略了什么。我尝试连接的设备是Bluegiga BLE113转接板。如果您能提供任何帮助，我们将不胜感激

下面是我所犯错误的解决方案。以前，清单文件中的BluetoothLeService引用是：

<service
    android:name="com.example.ble.BluetoothLeService"
    android:enabled="true" />

但这是另一个项目中的参考资料。一旦我把它改成：

<service
    android:name="com.example.ble_test2.BluetoothLeService"
    android:enabled="true" />

---

问题被纠正了

我从前面的评论中看到，您已经知道这是一个空指针异常。简单的回答是，在对mConnectionState调用setText方法之前，先检查它是否为null。像这样：

    public void run() {
        if (mConnectionState != null) {
            mConnectionState.setText(resourceId);
        }
    }

---

我认为发生的情况是，因为BroadcastReceiver异步启动，所以它在第141行调用super.onCreate和第152行将mConnection设置为实际TextView之间的某个位置启动。

出现空指针异常。我认为您的mBluetoothLeService从未被设置。异常表明它是第217行上的空指针，在optionsItemSelected方法内部。。。OnOptions ItemSelectedDeviceControlActivity.java:217感谢您如此快速的回复。我看到OnOptions ItemSelected出现了一个空点异常，但我不太确定这是什么意思。比如，当我尝试连接到设备时，它返回空值？因此错误来自我的清单文件。当我尝试连接时，它试图转到BluetoothLeService，但它不能，因为它在另一个项目中被引用。一旦我做出改变，就不再有问题了。再次感谢你的帮助！