我正在构建一个通过蓝牙与Arduino板通信的Android应用程序，我将蓝牙代码放在一个名为BlueComms的类中。要连接到设备，我使用以下方法：
public boolean connectDevice() {
CheckBt();
BluetoothDevice device = mBluetoothAdapter.getRemoteDevice(address);
Log.d(TAG, "Connecting to ... " + device);
mBluetoothAdapter.cancelDiscovery();
try {
btSocket = device.createRfcommSocketToServiceRecord(MY_UUID);
btSocket.connect();
outStream = btSocket.getOutputStream();
Log.d(TAG, "Connection made.");
return true;
} catch (IOException e) {
try {
btSocket.close();
} catch (IOException e2) {
Log.d(TAG, "Unable to end the connection");
return false;
}
Log.d(TAG, "Socket creation failed");
}
return false;
}
private void CheckBt() {
mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
if (!mBluetoothAdapter.isEnabled()) {
System.out.println("Bt dsbld");
}
if (mBluetoothAdapter == null) {
System.out.println("Bt null");
}
}
这种连接很好但是一旦我离开我通过它连接的活动就会断开连接，通过LogCat显示这个，
D/dalvikvm(21623): GC_CONCURRENT freed 103K, 10% free 2776K/3056K, paused 5ms+2ms, total 35ms
我无法再连接到设备，但是如果我调用killBt（）它会抛出一个致命错误，如果我尝试发送数据，我会收到'Socket creation failed'错误。我的发送消息代码如下：
public void sendData(String data, int recvAct) {
try {
outStream = btSocket.getOutputStream();
} catch (IOException e) {
Log.d(TAG, "Bug BEFORE Sending stuff", e);
}
String message = data;
byte[] msgBuffer = message.getBytes();
try {
outStream.write(msgBuffer);
} catch (IOException e) {
Log.d(TAG, "Bug while sending stuff", e);
}
}
当我切换不同的活动时，我应该如何防止连接被我连接的活动暂停，我正在使用以下代码切换活动：
Intent myIntent = new Intent(v.getContext(), Timelapse.class);
startActivityForResult(myIntent, 0);
非常感谢， ROZZ
答案 0 :(得分：10)
您在哪里存储BlueComms类的实例？如果你将它放在第一个活动中，那么当你离开它并移动到下一个活动时该类活动被销毁时类实例就会被杀死（NB活动也会在屏幕旋转时被破坏）
因此，只要您需要，就需要找到一种方法来保持BlueComms类的实例。您可以通过公共属性在活动之间传递它，并在轮换期间将其存储在onRetainNonConfigurationInstance（）中。
更简单的技巧是创建一个扩展Application的类，将其用作应用程序的应用程序委托，并向其添加公共属性以在其中存储BlueComms类的实例。这样，BlueComms类的实例将在你的app的生命周期中存活。
扩展申请
import android.app.Application;
public class cBaseApplication extends Application {
public BlueComms myBlueComms;
@Override
public void onCreate()
{
super.onCreate();
myBlueComms = new BlueComms();
}
}
使您的类成为应用程序清单中的应用程序委托
<application
android:name="your.app.namespace.cBaseApplication"
android:icon="@drawable/icon"
android:label="@string/app_name" >
从您的任何活动
访问基础应用((cBaseApplication)this.getApplicationContext()).myBlueComms.SomeMethod();
答案 1 :(得分：3)
我所做的是，为BluetoothConnection创建了一个单例类。 因此套接字创建只发生一次。
当创建任何活动的onCreate方法时，它首先获取BluetoothConnection类的实例。
Handler用于通过设置处理程序将来自BluetoothConnection类中的线程的消息发送到相应的活动。
像：
Class MyBTConnection{
private static MyBTConnection connectionObj;
private Handler mHandler;
public MyBTConnection() { //constructor }
public static MyBTConnection getInstance() {
if(connectionObj == null) {
connectionObj = new MyBTConnection();
}
return connectionObj;
}
}
public void setHandler(Handler handler) {
mHandler = handler;
}
..... Code for Bluetooth Connection ....
to send message :
mHandler.obtainMessage(what).sendToTarget();
}
// in first activity
class MainActivity extends Activity {
private MyBTConnection connectionObj;
public onCreate(....) {
/*
* Since this is first call for getInstance. A new object
* of MyBTConnection will be created and a connection to
* remote bluetooth device will be established.
*/
connectionObj = MyBTConnection.getInstance();
connectionObj.setHandler(mHandler);
}
private Handler mHandler = new Handler(){
public void onReceive(...) {
/// handle received messages here
}
};
}
// in second activity
class SecondActivity extends Activity {
private MyBTConnection connectionObj;
public onCreate(....) {
/*
* Since this is second call for getInstance.
* Object for MyBTConnection was already created in previous
* activity. So getInstance will return that previously
* created object and in that object, connection to remote
* bluetooth device is already established so you can
* continue your work here.
*/
connectionObj = MyBTConnection.getInstance();
connectionObj.setHandler(mHandler);
}
private Handler mHandler = new Handler(){
public void onReceive(...) {
/// handle received messages here
}
};
}
答案 2 :(得分：1)
我目前遇到了完全相同的问题，而且我想在每次活动要求时打开/关闭蓝牙套接字。每个Activity都有自己的BlueComms实例。
因为我的应用程序会变得有点复杂，并且会有来自不同活动的蓝牙线程请求，所以我认为这种方式将变得非常难以使用和排除故障。
我在这里读到的另一种方式...... https://developer.android.com/guide/components/services.html
可以在蓝牙插槽始终打开的背景上创建服务。可以使用Intent对此服务进行所有蓝牙请求。这也产生了相当多的复杂性，但感觉更加整洁和有条理。
我目前正处于这种困境，要么为每项活动使用线程，要么使用服务。我不知道哪条路实际上更好。
答案 3 :(得分：0)
当您选择要连接的设备时，当您单击设备列表项以请求连接到设备时，请使用AsyncTask 并将connect方法放在AsyncTask中，如下所示： -
AsyncTask.execute(new Runnable() {
@Override
public void run() {
try {
bluetoothSocket = Globals.bluetoothDevice.createRfcommSocketToServiceRecord(Globals.DEFAULT_SPP_UUID);
bluetoothSocket.connect();
// After successful connect you can open InputStream
} catch (IOException e) {
e.printStackTrace();
}
**Here is the full code for the same problem that i have cracked :-**
listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
lablelexconnected.setText("Connecting ...");
bdDevice = arrayListBluetoothDevices.get(position);
//bdClass = arrayListBluetoothDevices.get(position)
// Toast.makeText(getApplicationContext()," " + bdDevice.getAddress(),Toast.LENGTH_SHORT).show();
Log.i("Log", "The dvice : " + bdDevice.toString());
bdDevice = bluetoothAdapter.getRemoteDevice(bdDevice.getAddress());
Globals.bluetoothDevice = bluetoothAdapter.getRemoteDevice(bdDevice.getAddress());
System.out.println("Device in GPS Settings : " + bdDevice);
// startService(new Intent(getApplicationContext(),MyService.class));
/* Intent i = new Intent(GpsSettings.this, MyService.class);
startService(i);*/
// finish();
// connectDevice();
AsyncTask.execute(new Runnable() {
@Override
public void run() {
try {
bluetoothSocket = Globals.bluetoothDevice.createRfcommSocketToServiceRecord(Globals.DEFAULT_SPP_UUID);
bluetoothSocket.connect();
// After successful connect you can open InputStream
InputStream in = null;
in = bluetoothSocket.getInputStream();
InputStreamReader isr = new InputStreamReader(in);
br = new BufferedReader(isr);
while (found == 0) {
String nmeaMessage = br.readLine();
Log.d("NMEA", nmeaMessage);
// parse NMEA messages
sentence = nmeaMessage;
System.out.println("Sentence : " + sentence);
if (sentence.startsWith("$GPRMC")) {
String[] strValues = sentence.split(",");
System.out.println("StrValues : " + strValues[3] + " " + strValues[5] + " " + strValues[8]);
if (strValues[3].equals("") && strValues[5].equals("") && strValues[8].equals("")) {
Toast.makeText(getApplicationContext(), "Location Not Found !!! ", Toast.LENGTH_SHORT).show();
} else {
latitude = Double.parseDouble(strValues[3]);
if (strValues[4].charAt(0) == 'S') {
latitude = -latitude;
}
longitude = Double.parseDouble(strValues[5]);
if (strValues[6].charAt(0) == 'W') {
longitude = -longitude;
}
course = Double.parseDouble(strValues[8]);
// Toast.makeText(getApplicationContext(), "latitude=" + latitude + " ; longitude=" + longitude + " ; course = " + course, Toast.LENGTH_SHORT).show();
System.out.println("latitude=" + latitude + " ; longitude=" + longitude + " ; course = " + course);
// found = 1;
NMEAToDecimalConverter(latitude, longitude);
}
}
}
} catch (IOException e) {
e.printStackTrace();
}
}
});
}
});