Question

这是我的第一个Android应用程序，我正在尝试使用套接字将文本从我的计算机（服务器）发送到我的手机（客户端）。我以前用Java编程很多，但总是使用DrJava，而不是Eclipse，这是我必须用于Android编程的。

以下代码只是一个使用套接字的示例Java程序，我刚添加并删除了几行并将其粘贴到Android代码中。代码可在此处找到：http://zerioh.tripod.com/ressources/sockets.html 如果你不信任链接，你可以谷歌“java socket例子”。它应该是第一个链接。

我收到了一个未被捕获的异常错误，但我已经多次查看了代码，并且找不到没有catch行的地方。该代码适用于Java，但不适用于Android，因此我认为这是Android特定语法的一些问题。

以下是Android代码（客户端）：

package com.example.helloandroid;

import android.app.Activity;
import android.widget.TextView;
import android.os.Bundle;
import java.io.*;
import java.net.Socket;
import java.net.UnknownHostException;

public class HelloAndroid extends Activity {
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    //TextView tv = new TextView(this);
    //tv.setText("Eclipse is a horrible program");
    Requester client = new Requester();
    client.run();
    //setContentView(tv);
}
}

class Requester{
Socket requestSocket;
ObjectOutputStream out;
ObjectInputStream in;
String message;
void run()
{
    try{
        //1. creating a socket to connect to the server
        requestSocket = new Socket("localhost", 2004);
        System.out.println("Connected to localhost in port 2004");
        //2. get Input and Output streams
        out = new ObjectOutputStream(requestSocket.getOutputStream());
        out.flush();
        in = new ObjectInputStream(requestSocket.getInputStream());
        //3: Communicating with the server
        try{
            message = (String)in.readObject();
            System.out.println("server>" + message);
            sendMessage("asdfjksajdflksjdklfjsdklfjlsdf");
            message = "bye";
            sendMessage(message);
        }
        catch(ClassNotFoundException classNot){
            System.err.println("data received in unknown format");
        }
    }
    catch(UnknownHostException unknownHost) {
        System.err.println("You are trying to connect to an unknown host!");
    }
    catch(IOException ioException) {
        ioException.printStackTrace();
    }
    finally{
        //4: Closing connection
        try{
            in.close();
            out.close();
            requestSocket.close();
        }
        catch(IOException ioException){
            ioException.printStackTrace();
        }
    }
}
void sendMessage(String msg)
{
    try{
        out.writeObject(msg);
        out.flush();
        System.out.println("client>" + msg);
    }
    catch(Exception e) {
        e.printStackTrace();
    }
    /*catch(IOException ioException){
        ioException.printStackTrace();
    }*/
}
}

服务器代码与网站上的相同。

以下是我认为相关的catlog行。如果我错过了一些，请告诉我，我也会发布这些内容：

11-20 22:37:35.314: W/System.err(545): java.net.SocketException: Permission denied (maybe missing INTERNET permission)
11-20 22:37:35.324: W/System.err(545):  at org.apache.harmony.luni.platform.OSNetworkSystem.createStreamSocketImpl(Native Method)
11-20 22:37:35.324: W/System.err(545):  at org.apache.harmony.luni.platform.OSNetworkSystem.createStreamSocket(OSNetworkSystem.java:187)
11-20 22:37:35.324: W/System.err(545):  at org.apache.harmony.luni.net.PlainSocketImpl.create(PlainSocketImpl.java:266)
11-20 22:37:35.324: W/System.err(545):  at java.net.Socket.startupSocket(Socket.java:773)
11-20 22:37:35.324: W/System.err(545):  at java.net.Socket.tryAllAddresses(Socket.java:192)
11-20 22:37:35.324: W/System.err(545):  at java.net.Socket.<init>(Socket.java:256)
11-20 22:37:35.334: W/System.err(545):  at java.net.Socket.<init>(Socket.java:220)
11-20 22:37:35.334: W/System.err(545):  at com.example.helloandroid.Requester.run(HelloAndroid.java:33)
11-20 22:37:35.334: W/System.err(545):  at com.example.helloandroid.HelloAndroid.onCreate(HelloAndroid.java:19)
11-20 22:37:35.334: W/System.err(545):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
11-20 22:37:35.334: W/System.err(545):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2459)
11-20 22:37:35.334: W/System.err(545):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2512)
11-20 22:37:35.344: W/System.err(545):  at android.app.ActivityThread.access$2200(ActivityThread.java:119)
11-20 22:37:35.344: W/System.err(545):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1863)
11-20 22:37:35.344: W/System.err(545):  at android.os.Handler.dispatchMessage(Handler.java:99)
11-20 22:37:35.344: W/System.err(545):  at android.os.Looper.loop(Looper.java:123)
11-20 22:37:35.344: W/System.err(545):  at android.app.ActivityThread.main(ActivityThread.java:4363)
11-20 22:37:35.344: W/System.err(545):  at java.lang.reflect.Method.invokeNative(Native Method)
11-20 22:37:35.344: W/System.err(545):  at java.lang.reflect.Method.invoke(Method.java:521)
11-20 22:37:35.344: W/System.err(545):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:860)
11-20 22:37:35.344: W/System.err(545):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618)
11-20 22:37:35.354: W/System.err(545):  at dalvik.system.NativeStart.main(Native Method)
11-20 22:37:35.354: D/AndroidRuntime(545): Shutting down VM
11-20 22:37:35.354: W/dalvikvm(545): threadid=3: thread exiting with uncaught exception (group=0x4001b188)
11-20 22:37:35.354: E/AndroidRuntime(545): Uncaught handler: thread main exiting due to uncaught exception
11-20 22:37:35.364: E/AndroidRuntime(545): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.helloandroid/com.example.helloandroid.HelloAndroid}: java.lang.NullPointerException
11-20 22:37:35.364: E/AndroidRuntime(545):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2496)
11-20 22:37:35.364: E/AndroidRuntime(545):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2512)
11-20 22:37:35.364: E/AndroidRuntime(545):  at android.app.ActivityThread.access$2200(ActivityThread.java:119)
11-20 22:37:35.364: E/AndroidRuntime(545):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1863)
11-20 22:37:35.364: E/AndroidRuntime(545):  at android.os.Handler.dispatchMessage(Handler.java:99)
11-20 22:37:35.364: E/AndroidRuntime(545):  at android.os.Looper.loop(Looper.java:123)
11-20 22:37:35.364: E/AndroidRuntime(545):  at android.app.ActivityThread.main(ActivityThread.java:4363)
11-20 22:37:35.364: E/AndroidRuntime(545):  at java.lang.reflect.Method.invokeNative(Native Method)
11-20 22:37:35.364: E/AndroidRuntime(545):  at java.lang.reflect.Method.invoke(Method.java:521)
11-20 22:37:35.364: E/AndroidRuntime(545):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:860)
11-20 22:37:35.364: E/AndroidRuntime(545):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618)
11-20 22:37:35.364: E/AndroidRuntime(545):  at dalvik.system.NativeStart.main(Native Method)
11-20 22:37:35.364: E/AndroidRuntime(545): Caused by: java.lang.NullPointerException
11-20 22:37:35.364: E/AndroidRuntime(545):  at com.example.helloandroid.Requester.run(HelloAndroid.java:60)
11-20 22:37:35.364: E/AndroidRuntime(545):  at com.example.helloandroid.HelloAndroid.onCreate(HelloAndroid.java:19)
11-20 22:37:35.364: E/AndroidRuntime(545):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
11-20 22:37:35.364: E/AndroidRuntime(545):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2459)
11-20 22:37:35.364: E/AndroidRuntime(545):  ... 11 more
11-20 22:37:35.384: I/dalvikvm(545): threadid=7: reacting to signal 3
11-20 22:37:35.404: I/dalvikvm(545): Wrote stack trace to '/data/anr/traces.txt'

当我在Android模拟器上运行此代码时，它说：“抱歉！应用程序......已意外停止。请再试一次。”任何帮助将不胜感激！谢谢！

Answer 1

添加此标记

<uses-permission
        android:name="android.permission.INTERNET"></uses-permission>

在你的清单中

。

要求您在appplication中使用它之前添加访问互联网的权限

Answer 2

根据您的日志，您需要添加使用互联网权限。在你的清单中声明这个。

Answer 3

您需要在Android清单中使用INTERNET权限：

java.net.SocketException: Permission denied (maybe missing INTERNET permission)

如果in子句中out和finally Streams为空，则不会捕获Nullpointer异常。这些是null，因为它们从未打开过。

Android未捕获处理程序/未捕获的异常

3 个答案: