用于套接字连接的单例类不起作用

Question

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。 单身人士课程如下

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();
    }

}
  }

单击按钮时，将调用onClickon函数，该函数使用Singleton类的getSocket（）和getOutput（）函数来返回对象类型。

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)

Answer 1

一个主要的事情是你不能在远程连接等主线程上运行Costly操作，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

Answer 2

这段代码：

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？

将代码更改为这样可以在调用Singleton时避免出现此类问题且实例不存在。

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();
        }
    }
  }

Answer 3

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 ）。

Answer 4

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MainActivity的athead实现initSingleton（）

 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(); } } 

辛格尔顿（）

 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，但我认为你可以使用修改来运行你的`