我正在尝试为Android创建蓝牙聊天。 现在我的应用程序在禁用时激活蓝牙。点击后会有一个按钮可以找到所有附近启用了蓝牙功能的设备。我已经阅读了http://developer.android.com/guide/topics/connectivity/bluetooth.html中的指南，但我不明白为什么我的代码不起作用。 当我单击该按钮时，应用程序意外崩溃。 我在StackOverflow上已经阅读了几个问题，但我无法解决..
如果问题重复，我道歉，但我无法理解为什么它不起作用。
谢谢大家。
import java.util.Set;
import android.app.Activity;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBar;
import android.support.v7.app.ActionBarActivity;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;
public class MainActivity extends ActionBarActivity implements NavigationDrawerFragment.NavigationDrawerCallbacks {
// Intent request codes
private static final int REQUEST_CONNECT_DEVICE_SECURE = 1;
private static final int REQUEST_CONNECT_DEVICE_INSECURE = 2;
private static final int REQUEST_ENABLE_BT = 3;
// Message types sent from the BluetoothChatService Handler
public static final int MESSAGE_STATE_CHANGE = 1;
public static final int MESSAGE_READ = 2;
public static final int MESSAGE_WRITE = 3;
public static final int MESSAGE_DEVICE_NAME = 4;
public static final int MESSAGE_TOAST = 5;
// Key names received from the BluetoothChatService Handler
public static final String DEVICE_NAME = "device_name";
public static final String TOAST = "toast";
// Layout Views
private ListView mConversationView;
private EditText mOutEditText;
private Button mSendButton;
// Name of the connected device
private String mConnectedDeviceName = null;
// Array adapter for the conversation thread
private ArrayAdapter<String> mConversationArrayAdapter;
// String buffer for outgoing messages
private StringBuffer mOutStringBuffer;
// Local Bluetooth adapter
private BluetoothAdapter mBluetoothAdapter = null;
// Member object for the chat services
//private BluetoothChatService mChatService = null;
/**
* Fragment managing the behaviors, interactions and presentation of the navigation drawer.
*/
private NavigationDrawerFragment mNavigationDrawerFragment;
/**
* Used to store the last screen title. For use in {@link #restoreActionBar()}.
*/
private CharSequence mTitle;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Set up the window layout
setContentView(R.layout.activity_main);
mNavigationDrawerFragment = (NavigationDrawerFragment) getSupportFragmentManager().findFragmentById(R.id.navigation_drawer);
mTitle = getTitle();
// Set up the drawer.
mNavigationDrawerFragment.setUp(R.id.navigation_drawer,
(DrawerLayout) findViewById(R.id.drawer_layout));
// Get local Bluetooth adapter
mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
// If the adapter is null, then Bluetooth is not supported
if (mBluetoothAdapter == null) {
Toast.makeText(this, "Your device doesn't support Bluetooth.", Toast.LENGTH_LONG).show();
finish();
return;
}
}
@Override
public void onStart() {
super.onStart();
// If bluetooth is not on, request that it be enabled.
// setupChat() will then be called during onActivityResult
if (!mBluetoothAdapter.isEnabled()) {
Intent enableIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
startActivityForResult(enableIntent, REQUEST_ENABLE_BT);
}
// Otherwise, setup the chat session
else {
if (mChatService == null)
setupChat();
}
}
@Override
public synchronized void onResume() {
super.onResume();
// Performing this check in onResume() covers the case in which BT was
// not enabled during onStart(), so we were paused to enable it...
// onResume() will be called when ACTION_REQUEST_ENABLE activity returns.
if (mChatService != null) {
// Only if the state is STATE_NONE, do we know that we haven't started already
if (mChatService.getState() == BluetoothChatService.STATE_NONE) {
// Start the Bluetooth chat services
mChatService.start();
}
}
}
private void setupChat() {
// Initialize the array adapter for the conversation thread
mConversationArrayAdapter = new ArrayAdapter<String>(this, R.layout.message);
mConversationView = (ListView) findViewById(R.id.in);
mConversationView.setAdapter(mConversationArrayAdapter);
// Initialize the compose field with a listener for the return key
mOutEditText = (EditText) findViewById(R.id.edit_text_out);
mOutEditText.setOnEditorActionListener(mWriteListener);
// Initialize the send button with a listener that for click events
mSendButton = (Button) findViewById(R.id.button_send);
mSendButton.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
// Send a message using content of the edit text widget
TextView view = (TextView) findViewById(R.id.edit_text_out);
String message = view.getText().toString();
sendMessage(message);
}
});
// Initialize the BluetoothChatService to perform bluetooth connections
mChatService = new BluetoothChatService(this, mHandler);
// Initialize the buffer for outgoing messages
mOutStringBuffer = new StringBuffer("");
}
@Override
public synchronized void onPause() {
super.onPause();
}
@Override
public void onStop() {
super.onStop();
}
@Override
public void onDestroy() {
super.onDestroy();
// Stop the Bluetooth chat services
if (mChatService != null)
mChatService.stop();
}
@Override
public void onNavigationDrawerItemSelected(int position) {
// update the main content by replacing fragments
FragmentManager fragmentManager = getSupportFragmentManager();
fragmentManager.beginTransaction()
.replace(R.id.container, PlaceholderFragment.newInstance(position + 1))
.commit();
}
public void onSectionAttached(int number) {
switch (number) {
case 1:
mTitle = getString(R.string.title_section1);
break;
case 2:
mTitle = getString(R.string.title_section2);
break;
case 3:
mTitle = getString(R.string.title_section3);
break;
}
}
public void restoreActionBar() {
ActionBar actionBar = getSupportActionBar();
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_STANDARD);
actionBar.setDisplayShowTitleEnabled(true);
actionBar.setTitle(mTitle);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
if (!mNavigationDrawerFragment.isDrawerOpen()) {
// Only show items in the action bar relevant to this screen
// if the drawer is not showing. Otherwise, let the drawer
// decide what to show in the action bar.
getMenuInflater().inflate(R.menu.main, menu);
restoreActionBar();
return true;
}
return super.onCreateOptionsMenu(menu);
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
/**
* A placeholder fragment containing a simple view.
*/
public static class PlaceholderFragment extends Fragment {
/**
* The fragment argument representing the section number for this
* fragment.
*/
private static final String ARG_SECTION_NUMBER = "section_number";
/**
* Returns a new instance of this fragment for the given section
* number.
*/
public static PlaceholderFragment newInstance(int sectionNumber) {
PlaceholderFragment fragment = new PlaceholderFragment();
Bundle args = new Bundle();
args.putInt(ARG_SECTION_NUMBER, sectionNumber);
fragment.setArguments(args);
return fragment;
}
public PlaceholderFragment() {
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main, container, false);
TextView textView = (TextView) rootView.findViewById(R.id.section_label);
textView.setText(Integer.toString(getArguments().getInt(ARG_SECTION_NUMBER)));
return rootView;
}
@Override
public void onAttach(Activity activity) {
super.onAttach(activity);
((MainActivity) activity).onSectionAttached(
getArguments().getInt(ARG_SECTION_NUMBER));
}
}
/**************************************************
****** ADDED *************************************
*************************************************/
**/**
* Method associated with the button
*/**
public void scanForDevices(View view) {
// Querying paired devices
queryingPairedDevices(view);
// Discovering devices
discoveringDevices(view);
// Enabling discoverability
enablingDiscoverability(view);
}
public void queryingPairedDevices(View view) {
Set<BluetoothDevice> pairedDevices = mBluetoothAdapter.getBondedDevices();
// If there are paired devices
if(pairedDevices == null) {
//No Bonded Devices
Toast.makeText(getApplicationContext(), "No Bonded Devices", Toast.LENGTH_SHORT).show();
}
else {
if (pairedDevices.size() > 0) {
// Loop through paired devices
for (BluetoothDevice device : pairedDevices) {
// Add the name and address to an array adapter to show in a ListView
mConversationArrayAdapter.add(device.getName() + "\n" + device.getAddress());
}
mConversationArrayAdapter.add("End");
}
}
Toast.makeText(getApplicationContext(), "queryingPairedDevices", Toast.LENGTH_SHORT).show();
}
public void discoveringDevices(View view) {
// Create a BroadcastReceiver for ACTION_FOUND
//private final BroadcastReceiver mReceiver = new BroadcastReceiver() {
final BroadcastReceiver mReceiver = new BroadcastReceiver() {
@Override
public void onReceive(Context context, Intent intent) {
String action = intent.getAction();
// When discovery finds a device
if (BluetoothDevice.ACTION_FOUND.equals(action)) {
// Get the BluetoothDevice object from the Intent
BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
// Add the name and address to an array adapter to show in a ListView
mConversationArrayAdapter.add(device.getName() + "\n" + device.getAddress());
}
}
};
// Register the BroadcastReceiver
IntentFilter filter = new IntentFilter(BluetoothDevice.ACTION_FOUND);
registerReceiver(mReceiver, filter); // Don't forget to unregister during onDestroy
Toast.makeText(getApplicationContext(), "discoveringDevices", Toast.LENGTH_SHORT).show();
}
public void enablingDiscoverability(View view) {
if (mBluetoothAdapter.getScanMode() != BluetoothAdapter.SCAN_MODE_CONNECTABLE_DISCOVERABLE) {
Intent discoverableIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_DISCOVERABLE);
discoverableIntent.putExtra(BluetoothAdapter.EXTRA_DISCOVERABLE_DURATION, 300);
startActivity(discoverableIntent);
Toast.makeText(getApplicationContext(), "enablingDiscoverability", Toast.LENGTH_SHORT).show();
}
}
}
在日志中：
03-16 14:25:31.712: D/libEGL(984): loaded /vendor/lib/egl/libEGL_POWERVR_SGX540_120.so
03-16 14:25:31.727: D/libEGL(984): loaded /vendor/lib/egl/libGLESv1_CM_POWERVR_SGX540_120.so
03-16 14:25:31.735: D/libEGL(984): loaded /vendor/lib/egl/libGLESv2_POWERVR_SGX540_120.so
03-16 14:25:31.813: D/OpenGLRenderer(984): Enabling debug mode 0
03-16 14:25:32.001: I/ActivityManager(984): Timeline: Activity_idle id: android.os.BinderProxy@41ecdb40 time:38005382
03-16 14:26:07.977: I/ActivityManager(984): Timeline: Activity_idle id: android.os.BinderProxy@41f36520 time:38041356
03-16 14:26:11.157: I/ActivityManager(984): Timeline: Activity_idle id: android.os.BinderProxy@41f36520 time:38044534
03-16 14:26:16.376: D/AndroidRuntime(984): Shutting down VM
03-16 14:26:16.376: W/dalvikvm(984): threadid=1: thread exiting with uncaught exception (group=0x4167aba8)
03-16 14:26:16.384: E/AndroidRuntime(984): FATAL EXCEPTION: main
03-16 14:26:16.384: E/AndroidRuntime(984): Process: com.example.bchat, PID: 984
03-16 14:26:16.384: E/AndroidRuntime(984): java.lang.IllegalStateException: Could not execute method of the activity
03-16 14:26:16.384: E/AndroidRuntime(984): at android.view.View$1.onClick(View.java:3823)
03-16 14:26:16.384: E/AndroidRuntime(984): at android.view.View.performClick(View.java:4438)
03-16 14:26:16.384: E/AndroidRuntime(984): at android.view.View$PerformClick.run(View.java:18422)
03-16 14:26:16.384: E/AndroidRuntime(984): at android.os.Handler.handleCallback(Handler.java:733)
03-16 14:26:16.384: E/AndroidRuntime(984): at android.os.Handler.dispatchMessage(Handler.java:95)
03-16 14:26:16.384: E/AndroidRuntime(984): at android.os.Looper.loop(Looper.java:136)
03-16 14:26:16.384: E/AndroidRuntime(984): at android.app.ActivityThread.main(ActivityThread.java:5050)
03-16 14:26:16.384: E/AndroidRuntime(984): at java.lang.reflect.Method.invokeNative(Native Method)
03-16 14:26:16.384: E/AndroidRuntime(984): at java.lang.reflect.Method.invoke(Method.java:515)
03-16 14:26:16.384: E/AndroidRuntime(984): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
03-16 14:26:16.384: E/AndroidRuntime(984): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
03-16 14:26:16.384: E/AndroidRuntime(984): at dalvik.system.NativeStart.main(Native Method)
03-16 14:26:16.384: E/AndroidRuntime(984): Caused by: java.lang.reflect.InvocationTargetException
03-16 14:26:16.384: E/AndroidRuntime(984): at java.lang.reflect.Method.invokeNative(Native Method)
03-16 14:26:16.384: E/AndroidRuntime(984): at java.lang.reflect.Method.invoke(Method.java:515)
03-16 14:26:16.384: E/AndroidRuntime(984): at android.view.View$1.onClick(View.java:3818)
03-16 14:26:16.384: E/AndroidRuntime(984): ... 11 more
03-16 14:26:16.384: E/AndroidRuntime(984): Caused by: java.lang.NullPointerException
03-16 14:26:16.384: E/AndroidRuntime(984): at com.example.bchat.MainActivity.queryingPairedDevices(MainActivity.java:313)
03-16 14:26:16.384: E/AndroidRuntime(984): at com.example.bchat.MainActivity.scanForDevices(MainActivity.java:286)
03-16 14:26:16.384: E/AndroidRuntime(984): ... 14 more
03-16 14:26:18.368: I/Process(984): Sending signal. PID: 984 SIG: 9
第286行
queryingPairedDevices(view);
第313行
mConversationArrayAdapter.add(device.getName() + "\n" + device.getAddress());