Android蓝牙应用程序在点击按钮时崩溃，我已经用Google搜索了问题，但是得到了相关的答案。请帮助我是android的新手。 我正在使用android studio创建一个蓝牙应用程序，每当我点击连接设备按钮时它就会崩溃。下面是我认为错误的代码。
DeviceActivity.java
package com.contec.activity;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.Set;
import java.util.UUID;
import com.contec.spmw.R;
import android.app.Activity;
import android.app.AlertDialog;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.bluetooth.BluetoothSocket;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.content.IntentFilter;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.AdapterView;
import android.widget.Button;
import android.widget.ListView;
import android.widget.Toast;
import android.widget.AdapterView.OnItemClickListener;
public class DeviceActivity extends Activity {
/** Called when the activity is first created. */
private ListView mListView;
private ArrayList<SiriListItem> list;
private Button seachButton, serviceButton;
ChatListAdapter mAdapter;
Context mContext;
private String mstraddress = "";
private BluetoothAdapter mBtAdapter = BluetoothAdapter.getDefaultAdapter();
@Override
public void onStart() {
super.onStart();
// If BT is not on, request that it be enabled.
if (!mBtAdapter.isEnabled()) {
Intent enableIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
startActivityForResult(enableIntent, 3);
}
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.devices);
mContext = this;
init();
}
private void init() {
list = new ArrayList<SiriListItem>();
mAdapter = new ChatListAdapter(this, list);
mListView = (ListView) findViewById(R.id.list);
mListView.setAdapter(mAdapter);
mListView.setFastScrollEnabled(true);
mListView.setOnItemClickListener(mDeviceClickListener);
// Register for broadcasts when discovery has finished
IntentFilter foundFilter = new IntentFilter(BluetoothDevice.ACTION_FOUND);
this.registerReceiver(mReceiver, foundFilter);
// Register for broadcasts when a device is discovered
IntentFilter discoveryFilter = new IntentFilter(BluetoothAdapter.ACTION_DISCOVERY_FINISHED);
this.registerReceiver(mReceiver, discoveryFilter);
// Get a set of currently paired devices
Set<BluetoothDevice> pairedDevices = mBtAdapter.getBondedDevices();
// If there are paired devices, add each one to the ArrayAdapter
if (pairedDevices.size() > 0) {
for (BluetoothDevice device : pairedDevices) {
list.add(new SiriListItem(device.getName() + "\n" + device.getAddress(), true));
mAdapter.notifyDataSetChanged();
mListView.setSelection(list.size() - 1);
}
} else {
list.add(new SiriListItem("Some CHinese Text", true));
mAdapter.notifyDataSetChanged();
mListView.setSelection(list.size() - 1);
}
seachButton = (Button)findViewById(R.id.start_seach);
seachButton.setOnClickListener(seachButtonClickListener);
}
private OnClickListener seachButtonClickListener = new OnClickListener() {
@Override
public void onClick(View arg0) {
// TODO Auto-generated method stub
if(mBtAdapter.isDiscovering())
{
mBtAdapter.cancelDiscovery();
//seachButton.setText("重新搜索");
seachButton.setText("Re Find");
}
else
{
list.clear();
mAdapter.notifyDataSetChanged();
Set<BluetoothDevice> pairedDevices = mBtAdapter.getBondedDevices();
if (pairedDevices.size() > 0) {
for (BluetoothDevice device : pairedDevices) {
list.add(new SiriListItem(device.getName() + "\n" + device.getAddress(), true));
mAdapter.notifyDataSetChanged();
mListView.setSelection(list.size() - 1);
}
} else {
list.add(new SiriListItem("No devices have been paired", true));
mAdapter.notifyDataSetChanged();
mListView.setSelection(list.size() - 1);
}
mBtAdapter.startDiscovery();
//seachButton.setText("Some Chinese Text");
seachButton.setText("stop");
}
}
};
// The on-click listener for all devices in the ListViews
private OnItemClickListener mDeviceClickListener = new OnItemClickListener() {
public void onItemClick(AdapterView<?> av, View v, int arg2, long arg3) {
// Cancel discovery because it's costly and we're about to connect
SiriListItem item = list.get(arg2);
String info = item.message;
mstraddress = info.substring(info.length() - 17);
// Bluetooth.BlueToothAddress = address;
AlertDialog.Builder StopDialog =new AlertDialog.Builder(mContext);
//StopDialog.setTitle("Some CHinese Text");
StopDialog.setTitle("connect");
StopDialog.setMessage(item.message);
//StopDialog.setPositiveButton("Some CHinese Text", new DialogInterface.OnClickListener() {
StopDialog.setPositiveButton("connect", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
// TODO Auto-generated method stub
mBtAdapter.cancelDiscovery();
//seachButton.setText("Some Chinese Text");
seachButton.setText("Re find");
// Bluetooth.serviceOrCilent=ServerOrCilent.CILENT;
// Bluetooth.mTabHost.setCurrentTab(1);
if(!mstraddress.equals("null"))
{
//device = mBtAdapter.getRemoteDevice(mstraddress);
//clientConnectThread = new clientThread();
//clientConnectThread.start();
Intent intent2 = new Intent();
intent2.setClass(DeviceActivity.this, MainActivity.class);
Bundle bundle = new Bundle();
bundle.putString("straddress", mstraddress);
intent2.putExtra("bundle", bundle);
setResult(0, intent2);
DeviceActivity.this.finish();
}
else
{
Toast.makeText(DeviceActivity.this, "address is null !", Toast.LENGTH_SHORT).show();
}
}
});
//StopDialog.setNegativeButton("Some CHinese Text",new DialogInterface.OnClickListener() {
StopDialog.setNegativeButton("cancel",new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
// Bluetooth.BlueToothAddress = null;
}
});
StopDialog.show();
}
};
private Handler LinkDetectedHandler = new Handler() {
@Override
public void handleMessage(Message msg) {
if (msg.what == 0)
{
Toast.makeText(mContext, (String)msg.obj, Toast.LENGTH_SHORT).show();
}
else if (msg.what == 1)
{
String str = "Some chinese Text：\r\n" + (String)msg.obj;
Toast.makeText(mContext, str, Toast.LENGTH_SHORT).show();//测试
}
}
};
// The BroadcastReceiver that listens for discovered devices and
// changes the title when discovery is finished
private 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);
// If it's already paired, skip it, because it's been listed already
if (device.getBondState() != BluetoothDevice.BOND_BONDED)
{
list.add(new SiriListItem(device.getName() + "\n" + device.getAddress(), false));
mAdapter.notifyDataSetChanged();
mListView.setSelection(list.size() - 1);
}
// When discovery is finished, change the Activity title
}
else if (BluetoothAdapter.ACTION_DISCOVERY_FINISHED.equals(action))
{
setProgressBarIndeterminateVisibility(false);
if (mListView.getCount() == 0)
{
//list.add(new SiriListItem("Some CHinese Text", false));
list.add(new SiriListItem("not find bluetooth", false));
mAdapter.notifyDataSetChanged();
mListView.setSelection(list.size() - 1);
}
//seachButton.setText("Some CHinese Text");
seachButton.setText("Re find");
}
}
};
public class SiriListItem {
String message;
boolean isSiri;
public SiriListItem(String msg, boolean siri) {
message = msg;
isSiri = siri;
}
}
@Override
protected void onDestroy() {
super.onDestroy();
// Make sure we're not doing discovery anymore
if (mBtAdapter != null) {
mBtAdapter.cancelDiscovery();
}
// Unregister broadcast listeners
this.unregisterReceiver(mReceiver);
}
}
logcat的
--------- beginning of crash
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.contec.spmw, PID: 1937
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.contec.spmw/com.contec.activity.DeviceActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.util.Set android.bluetooth.BluetoothAdapter.getBondedDevices()' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2298)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
at android.app.ActivityThread.access$800(ActivityThread.java:144)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5221)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.util.Set android.bluetooth.BluetoothAdapter.getBondedDevices()' on a null object reference
at com.contec.activity.DeviceActivity.init(DeviceActivity.java:227)
at com.contec.activity.DeviceActivity.onCreate(DeviceActivity.java:204)
at android.app.Activity.performCreate(Activity.java:5937)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2251)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
at android.app.ActivityThread.access$800(ActivityThread.java:144)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5221)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
I/Process: Sending signal. PID: 1937 SIG: 9
Application terminated.
答案 0 :(得分：1)
在调用BluetoothAdapter之前尝试检查getBondedDevices是否为空，因为如果您的设备不支持蓝牙，它将返回null。根据您在问题中的评论，Android模拟器不支持蓝牙。请在documentation中查看。
BluetoothAdapter - 默认本地适配器，如果此硬件平台不支持蓝牙，则为null
检查如下：
if (mBtAdapter != null && mBtAdapter.isEnabled()) {
// do your task
Set<BluetoothDevice> pairedDevices = mBtAdapter.getBondedDevices();
} else {
// Bluetooth is not supported on your hardware
}
希望它对你有所帮助。