我创建了一个单例类来启用套接字连接，它返回一个套接字对象，可以被应用程序中的任意数量的活动使用。 单例类如下
public class Singleton
{
private static Socket socket;
private DataInputStream input;
private DataOutputStream output;
private boolean logged;
private static Singleton instance;
private String information;
private static final int SERVERPORT = 8020;
private static final String SERVER_IP = "192.168.1.33";
static PrintWriter out;
private Singleton()
{
}
public static Singleton getInstance()
{
return instance;
}
public static void initSingleton()
{
if(instance == null)
{
instance = new Singleton();
InetAddress serverAddr = null;
try {
serverAddr = InetAddress.getByName(SERVER_IP);
} catch (UnknownHostException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
try {
socket = new Socket(serverAddr, SERVERPORT);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
try {
out = new PrintWriter(new BufferedWriter(
new OutputStreamWriter(socket.getOutputStream())),
true);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
public Socket getSocket()
{
return socket;
}
public PrintWriter getOutput()
{
return out;
}
}
在MainActivity中，我调用单例类。
public class MainActivity extends Activity implements OnItemSelectedListener {
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
initSingleton(); }
protected void initSingleton()
{
Singleton.initSingleton();
}
public void onClickon(View view) {
Socket socket = Singleton.getInstance().getSocket();
try{
PrintWriter out=Singleton.getInstance().getOutput();
out.println("0");
}
catch (Exception e) {
e.printStackTrace();
}
}
}
按钮单击，调用onClickon函数，该函数使用Singleton类的getSocket（）和getOutput（）函数返回对象类型。
但应用程序崩溃了。
日志如下。
05-08 11:33:41.236: E/AndroidRuntime(19813): FATAL EXCEPTION: main
05-08 11:33:41.236: E/AndroidRuntime(19813): Process: com.example.clientmobile2, PID: 19813
05-08 11:33:41.236: E/AndroidRuntime(19813): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.clientmobile2/com.example.clientmobile2.MainActivity}: android.os.NetworkOnMainThreadException
05-08 11:33:41.236: E/AndroidRuntime(19813): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2209)
05-08 11:33:41.236: E/AndroidRuntime(19813): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2269)
05-08 11:33:41.236: E/AndroidRuntime(19813): at android.app.ActivityThread.access$800(ActivityThread.java:139)
05-08 11:33:41.236: E/AndroidRuntime(19813): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1210)
05-08 11:33:41.236: E/AndroidRuntime(19813): at android.os.Handler.dispatchMessage(Handler.java:102)
05-08 11:33:41.236: E/AndroidRuntime(19813): at android.os.Looper.loop(Looper.java:136)
05-08 11:33:41.236: E/AndroidRuntime(19813): at android.app.ActivityThread.main(ActivityThread.java:5102)
05-08 11:33:41.236: E/AndroidRuntime(19813): at java.lang.reflect.Method.invokeNative(Native Method)
05-08 11:33:41.236: E/AndroidRuntime(19813): at java.lang.reflect.Method.invoke(Method.java:515)
05-08 11:33:41.236: E/AndroidRuntime(19813): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
05-08 11:33:41.236: E/AndroidRuntime(19813): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
05-08 11:33:41.236: E/AndroidRuntime(19813): at dalvik.system.NativeStart.main(Native Method)
05-08 11:33:41.236: E/AndroidRuntime(19813): Caused by: android.os.NetworkOnMainThreadException
05-08 11:33:41.236: E/AndroidRuntime(19813): at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1145)
05-08 11:33:41.236: E/AndroidRuntime(19813): at libcore.io.BlockGuardOs.connect(BlockGuardOs.java:84)
05-08 11:33:41.236: E/AndroidRuntime(19813): at libcore.io.IoBridge.connectErrno(IoBridge.java:127)
05-08 11:33:41.236: E/AndroidRuntime(19813): at libcore.io.IoBridge.connect(IoBridge.java:112)
05-08 11:33:41.236: E/AndroidRuntime(19813): at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:192)
05-08 11:33:41.236: E/AndroidRuntime(19813): at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:172)
05-08 11:33:41.236: E/AndroidRuntime(19813): at java.net.Socket.startupSocket(Socket.java:566)
05-08 11:33:41.236: E/AndroidRuntime(19813): at java.net.Socket.<init>(Socket.java:226)
05-08 11:33:41.236: E/AndroidRuntime(19813): at com.example.clientmobile2.Singleton.initSingleton(Singleton.java:48)
05-08 11:33:41.236: E/AndroidRuntime(19813): at com.example.clientmobile2.MainActivity.initSingleton(MainActivity.java:148)
05-08 11:33:41.236: E/AndroidRuntime(19813): at com.example.clientmobile2.MainActivity.onCreate(MainActivity.java:101)
05-08 11:33:41.236: E/AndroidRuntime(19813): at android.app.Activity.performCreate(Activity.java:5248)
05-08 11:33:41.236: E/AndroidRuntime(19813): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1110)
05-08 11:33:41.236: E/AndroidRuntime(19813): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2173)
答案 0 :(得分：2)
一个主要的事情是你无法在远程连接等主线程上运行Costly操作.. e.t.c， 我的意思是你为这个套接字连接创建新线程，否则使用异步任务将重新解决你的问题。
注意：请不要忘记关闭连接
答案 1 :(得分：1)
此代码：
protected void initSingleton()
{
Singleton.initSingleton();
}
在尝试获取实例之前未执行，即使您正在调用该函数onCreate()。为什么要在单独的方法上实例化Singleton而不是在getInstance()中实例化它？
将代码更改为这样，以便在调用Singleton时避免此类问题，并且实例不存在。
public static Singleton getInstance()
{
if(instance == null)
initSingleton();
return instance;
}
private static void initSingleton()
{
instance = new Singleton();
InetAddress serverAddr = null;
try
{
serverAddr = InetAddress.getByName(SERVER_IP);
}
catch (UnknownHostException e)
{
System.err.println("Fail when getting Server Address.");
}
try
{
socket = new Socket(serverAddr, SERVERPORT);
}
catch (IOException e)
{
System.err.println("Failed creating new socket.");
}
try
{
out = new PrintWriter(new BufferedWriter(
new OutputStreamWriter(socket.getOutputStream())),
true);
}
catch (IOException e)
{
System.err.println("EPIC FAIL HERE");
}
}
主要活动：
public class MainActivity extends Activity implements OnItemSelectedListener
{
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
public void onClickon(View view)
{
Socket socket = Singleton.getInstance().getSocket();
try
{
PrintWriter out=Singleton.getInstance().getOutput();
out.println("0");
}
catch (Exception e)
{
e.printStackTrace();
}
}
}
答案 2 :(得分：0)
FunctionR的解决方案是正确的，但它不是线程安全的，因此一个解决方案可以是在静态初始化程序中实例化单例变量，或者使用synchronized块来使单例实例化线程安全（http://www.jguru.com/faq/view.jsp?EID=124425）。 / p>
答案 3 :(得分：0)
嗨，我尝试了我们的代码，我做了一些修改，它工作正常，我实例化套接字并在执行中的athead实现initSingleton（） MainActivity
public class ConnectActivity extends Activity {
Socket clientSocket;
Singleton instance;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_connect);
instance=new Singleton();
new Thread(new ClientThread()).start();
//Socket socket = Singleton.getInstance().getSocket();
}
protected void initSingleton()
{
instance.initSingleton();
}
class ClientThread implements Runnable {
@Override
public void run() {
initSingleton();
Socket socket = Singleton.getInstance().getSocket();
}
}
单例（）
public class Singleton {
public static Socket clientSocket;
/* private DataInputStream input;
private DataOutputStream output;*/
private boolean logged;
public static Singleton instance;
public static String information;
public static int SERVER_PORT;
public static String SERVER_IP;
/*static PrintWriter out;*/
public Singleton() {
}
public Singleton(int server_port, String server_ip) {
SERVER_PORT = server_port;
SERVER_IP = server_ip;
}
public static Singleton getInstance() {
return instance;
}
public static void initSingleton() {
if (instance == null) {
instance = new Singleton();
InetAddress serverAddr = null;
try {
serverAddr = InetAddress.getByName(SERVER_IP);
information=SERVER_IP;
} catch (UnknownHostException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
try {
clientSocket = new Socket(information, SERVER_PORT);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
public Socket getSocket() {
return clientSocket;
}
}
我将代码更改为我的项目，但我认为您可以使用修改来运行您的“