我正在尝试制作一个简单的应用程序，它可以发送来自EditText 的消息，
使用 Java Socket 类。我正在尝试使用AsyncTask，但它只工作一次，我无法返回套接字以在该类的另一个实例中重用。
你能给我一个后台服务的例子吗？它打开与服务器的通信并返回套接字？
编辑：
nandsito 要求；我打算使用Button 打开一个连接，所以这个按钮调用一个后台进程来创建与服务器的连接，最后返回Socket。当我按下另一个 Button 时，我想启动另一个重用套接字的任务，写入数据（例如 Sring）接收来自服务器的响应并更新 UI。
【问题讨论】：
标签： java android sockets android-asynctask android-service
看起来很简单，但我认为您遇到了一个有趣且具有挑战性的问题。如果您想在通过它发送消息后保持套接字打开，则需要维护一个或多个线程来使用该套接字，因为您知道，Android 不允许在主线程上联网。
多线程编程很少是简单的，而且通常有不止一种方法可以做到这一点。例如。在 Android 中，您可以将 Handlers 与来自 HandlerThreads 的 Loopers 或经典的 Java Thread 一起使用。还有AsyncTask，但我认为它不适合这种情况。
您打算如何管理套接字生命周期（即它何时打开或关闭），以及数据在哪些时刻从套接字读取/写入/写入套接字？请更好地解释此事，以便我提出实施建议。
编辑
这是一个带有两个按钮的示例Activity。一个按钮运行AsyncTask 创建套接字及其流，另一个按钮运行另一个AsyncTask 将数据写入套接字。这是一个过于简单的解决方案，但它应该可以工作。请注意，代码需要同步，以便不同的线程访问套接字。
public class MainActivity extends Activity {
private SocketContainer mSocketContainer;
private final Object mSocketContainerLock = new Object();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
// onClick attribute of one button.
public void onClickPushMe(View view) {
String serverAddress;
int serverPort;
new CreateSocketAsyncTask(serverAddress, serverPort).execute();
}
// onClick attribute of other button.
public void onClickPushMeToo(View view) {
String text;
new WriteSocketAsyncTask(text).execute();
}
// Class that contains the socket and its streams,
// so they can be passed from one thread to another.
private class SocketContainer {
private Socket mSocket;
private InputStream mSocketInputStream;
private OutputStream mSocketOutputStream;
private SocketContainer(Socket socket, InputStream socketInputStream, OutputStream socketOutputStream) {
mSocket = socket;
mSocketInputStream = socketInputStream;
mSocketOutputStream = socketOutputStream;
}
private Socket getSocket() {
return mSocket;
}
private InputStream getSocketInputStream() {
return mSocketInputStream;
}
private OutputStream getSocketOutputStream() {
return mSocketOutputStream;
}
}
// AsyncTask that creates a SocketContainer and sets in into MainActivity.
private class CreateSocketAsyncTask extends AsyncTask<Void, Void, SocketContainer> {
private final String mServerAddress;
private final int mServerPort;
private CreateSocketAsyncTask(String serverAddress, int serverPort) {
mServerAddress = serverAddress;
mServerPort = serverPort;
}
protected SocketContainer doInBackground(Void... params) {
try {
Socket socket = new Socket(mServerAddress, mServerPort);
return new SocketContainer(socket, socket.getInputStream(), socket.getOutputStream());
} catch (IOException e) {
throw new RuntimeException(e);
}
}
@Override
protected void onPostExecute(SocketContainer socketContainer) {
super.onPostExecute(socketContainer);
synchronized (mSocketContainerLock) {
mSocketContainer = socketContainer;
}
}
}
private class WriteSocketAsyncTask extends AsyncTask<Void, Void, Void> {
private final String mText;
private WriteSocketAsyncTask(String text) {
mText = text;
}
@Override
protected Void doInBackground(Void... params) {
synchronized (mSocketContainerLock) {
try {
mSocketContainer.getSocketOutputStream().write(mText.getBytes(Charset.forName("UTF-8")));
mSocketContainer.getSocketOutputStream().flush();
} catch (IOException e) {
throw new RuntimeException(e);
}
}
return null;
}
}
}
【讨论】：
mSocketContainerLock 放置一个getter，为mSocketContainer 放置一个getter 和setter，并将MainActivity 实例传递给AsyncTasks 构造函数，这样您就可以执行@ 之类的操作987654335@ 但是（1）这个解决方案会变得非常复杂，（2）它可能会泄漏Context：android-developers.blogspot.com.br/2009/01/…
使用此代码，我可以连接到聊天室，因此您可以使用它来连接您想要的内容
public class SocialConnectionManager extends AsyncTask<Void, Void, Void> {
public static final int SQL_STEP_LOGIN = 0;
public static final int SQL_STEP_LOGOUT = 1;
public static final int SQL_STEP_SEND = 2;
public static final int SQL_STEP_UPDATE = 3;
final int serverPort = 8080;
private String message, channel, userName, serverIp;
private int step;
private long uniqueId;
private Activity activity;
public SocialConnectionManager(String serverIp, long uniqueId, int step, String userName,
String channel, String message, Activity activity) {
this.message = message;
this.step = step;
this.uniqueId = uniqueId;
this.channel = channel;
this.userName = userName;
this.serverIp = serverIp;
this.activity = activity;
}
@Override
protected Void doInBackground(Void... arg0) {
Socket socket = null;
try {
socket = new Socket(serverIp, serverPort);
DataOutputStream dataOut = new DataOutputStream(socket.getOutputStream());
switch (step) {
case SQL_STEP_LOGIN:
dataOut.writeInt(step);
dataOut.writeLong(uniqueId);
dataOut.writeUTF(channel);
dataOut.writeUTF(userName);
break;
case SQL_STEP_LOGOUT:
dataOut.writeInt(step);
dataOut.writeLong(uniqueId);
dataOut.writeUTF(channel);
dataOut.writeUTF(userName);
break;
case SQL_STEP_SEND:
long messageId = createRandomId();
messageIds.add(messageId);
dataOut.writeInt(step);
dataOut.writeLong(uniqueId);
dataOut.writeUTF(channel);
dataOut.writeUTF(userName);
dataOut.writeUTF(message);
dataOut.writeLong(messageId);
break;
case SQL_STEP_UPDATE:
dataOut.writeInt(step);
dataOut.writeUTF(message);
break;
}
dataOut.flush();
} catch (UnknownHostException e) {
activity.runOnUiThread(new Runnable() {
@Override
public void run() {
((MainActivity) activity).showNetworkAlertDialog(context.getString
(R.string.social_chat_connection_failed));
}
});
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
if (socket != null) {
try {
socket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
return null;
}
@Override
protected void onPostExecute(Void result) {
super.onPostExecute(result);
}
}
private class ReceiveTask extends AsyncTask {
final int clientPort = 5050;
@Override
protected Object doInBackground(Object[] params) {
try {
serverSocket = new ServerSocket(clientPort);
while (true) {
final Socket socket = serverSocket.accept();
DataInputStream dataIn = new DataInputStream(socket.getInputStream());
final int step = dataIn.readInt();
final int userCount = dataIn.readInt();
final String message = dataIn.readUTF();
final String userName = dataIn.readUTF();
switch (step) {
case SocialConnectionManager.SQL_STEP_LOGIN:
if (isLogging) {
activity.runOnUiThread(new Runnable() {
@Override
public void run() {
showProgress(false);
}
});
isLogging = false;
isLoggedIn = true;
}
activity.runOnUiThread(new Runnable() {
@Override
public void run() {
userCountView.setText(Integer.toString(userCount));
addMessage(message, userName, step);
}
});
break;
case SocialConnectionManager.SQL_STEP_LOGOUT:
activity.runOnUiThread(new Runnable() {
@Override
public void run() {
addMessage(message, userName, step);
}
});
break;
case SocialConnectionManager.SQL_STEP_SEND:
messageId = dataIn.readLong();
activity.runOnUiThread(new Runnable() {
@Override
public void run() {
addMessage(message, userName, step);
}
});
break;
}
}
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
}
BroadcastReceiver networkStateReceiver = new BroadcastReceiver() {
@Override
public void onReceive(Context context, Intent intent) {
String ip = getIpAddress();
if (ip.equals("")) {
((MainActivity) activity).showNetworkAlertDialog(context.getString
(R.string.social_chat_connection_lost));
} else if (!deviceIp.equals(ip)) {
SocialConnectionManager socialConnectionManager =
new SocialConnectionManager(serverIp, 0,
SocialConnectionManager.SQL_STEP_UPDATE, null, null, deviceIp,
activity);
socialConnectionManager.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
}
}
};
}
【讨论】：
异步任务不适合实时聊天。 进入firebase以轻松使用这些东西。 这可能会帮助你- https://www.firebase.com/docs/android/examples.html
【讨论】：