我是Android编程新手。
我正在尝试在eclipse中进行非常简单的客户端/服务器TCP通信。服务器端使用java类，客户端使用Android应用程序。我从eclipse启动应用程序，而不是在模拟器上，而是在USB连接的手机上启动。
问题所在。当我从xml清单文件中删除INTERNET权限代码行时，应用程序不会崩溃，但它也不会连接（服务器控制台中没有消息）。但是，如果我确实将INTERNET权限代码放入，则应用程序会崩溃并显示消息“Unfortunately APP_NAME has stopped”。
任何人都可以指出我错过了什么吗？
代码如下：
服务器（java）类：
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.ServerSocket;
import java.net.Socket;
public class Main {
private static ServerSocket serverSocket = null;
private static Socket clientSocket;
private static InputStreamReader inputStreamReader;
private static BufferedReader bufferedReader;
private static String message;
public static void main(String[] args) {
try {
serverSocket = new ServerSocket(4444); //Server socket
} catch (IOException e) {
System.out.println("Could not listen on port: 4444");
}
System.out.println("Server started. Listening to the port 4444");
while (true) {
try {
clientSocket = serverSocket.accept(); //accept the client connection
inputStreamReader = new InputStreamReader(clientSocket.getInputStream());
bufferedReader = new BufferedReader(inputStreamReader); //get the client message
message = bufferedReader.readLine();
System.out.println(message);
inputStreamReader.close();
clientSocket.close();
} catch (IOException ex) {
System.out.println("Problem in message reading");
}
}
}
}
客户端（android）活动文件：
package com.example.simpleclient;
import java.io.IOException;
import java.io.PrintWriter;
import java.net.Socket;
import java.net.UnknownHostException;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
public class SimpleClientActivity extends Activity {
private Socket client;
private PrintWriter printwriter;
private EditText textField;
private Button button;
private String messsage;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
textField = (EditText) findViewById(R.id.editText1); //reference to the text field
button = (Button) findViewById(R.id.button1); //reference to the send button
//Button press event listener
button.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
messsage = textField.getText().toString(); //get the text message on the text field
textField.setText(""); //Reset the text field to blank
try {
client = new Socket("127.0.0.1", 4444); //connect to server
printwriter = new PrintWriter(client.getOutputStream(), true);
printwriter.write(messsage); //write the message to output stream
printwriter.flush();
printwriter.close();
client.close(); //closing the connection
} catch (UnknownHostException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
});
}
}
客户端xml清单文件：
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.simpleclient"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="21" />
<uses-permission android:name="android.permission.INTERNET" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name=".SimpleClientActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
- 编辑 - 的 logcat的：
01-21 21:40:55.012: D/libEGL(17722): loaded /vendor/lib/egl/libEGL_adreno.so
01-21 21:40:55.022: D/libEGL(17722): loaded /vendor/lib/egl/libGLESv1_CM_adreno.so
01-21 21:40:55.042: D/libEGL(17722): loaded /vendor/lib/egl/libGLESv2_adreno.so
01-21 21:40:55.042: I/Adreno-EGL(17722): <qeglDrvAPI_eglInitialize:316>: EGL 1.4 QUALCOMM build: (CL4169980)
01-21 21:40:55.042: I/Adreno-EGL(17722): OpenGL ES Shader Compiler Version: 17.01.10.SPL
01-21 21:40:55.042: I/Adreno-EGL(17722): Build Date: 09/26/13 Thu
01-21 21:40:55.042: I/Adreno-EGL(17722): Local Branch:
01-21 21:40:55.042: I/Adreno-EGL(17722): Remote Branch:
01-21 21:40:55.042: I/Adreno-EGL(17722): Local Patches:
01-21 21:40:55.042: I/Adreno-EGL(17722): Reconstruct Branch:
01-21 21:40:55.163: D/OpenGLRenderer(17722): Enabling debug mode 0
01-21 21:40:57.875: D/AndroidRuntime(17722): Shutting down VM
01-21 21:40:57.875: W/dalvikvm(17722): threadid=1: thread exiting with uncaught exception (group=0x4190a898)
01-21 21:40:57.885: E/AndroidRuntime(17722): FATAL EXCEPTION: main
01-21 21:40:57.885: E/AndroidRuntime(17722): android.os.NetworkOnMainThreadException
01-21 21:40:57.885: E/AndroidRuntime(17722): at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1144)
01-21 21:40:57.885: E/AndroidRuntime(17722): at libcore.io.BlockGuardOs.connect(BlockGuardOs.java:84)
01-21 21:40:57.885: E/AndroidRuntime(17722): at libcore.io.IoBridge.connectErrno(IoBridge.java:127)
01-21 21:40:57.885: E/AndroidRuntime(17722): at libcore.io.IoBridge.connect(IoBridge.java:112)
01-21 21:40:57.885: E/AndroidRuntime(17722): at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:192)
01-21 21:40:57.885: E/AndroidRuntime(17722): at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:172)
01-21 21:40:57.885: E/AndroidRuntime(17722): at java.net.Socket.startupSocket(Socket.java:566)
01-21 21:40:57.885: E/AndroidRuntime(17722): at java.net.Socket.tryAllAddresses(Socket.java:127)
01-21 21:40:57.885: E/AndroidRuntime(17722): at java.net.Socket.<init>(Socket.java:177)
01-21 21:40:57.885: E/AndroidRuntime(17722): at java.net.Socket.<init>(Socket.java:149)
01-21 21:40:57.885: E/AndroidRuntime(17722): at com.example.simpleclient.SimpleClientActivity$1.onClick(SimpleClientActivity.java:41)
01-21 21:40:57.885: E/AndroidRuntime(17722): at android.view.View.performClick(View.java:4475)
01-21 21:40:57.885: E/AndroidRuntime(17722): at android.view.View$PerformClick.run(View.java:18786)
01-21 21:40:57.885: E/AndroidRuntime(17722): at android.os.Handler.handleCallback(Handler.java:730)
01-21 21:40:57.885: E/AndroidRuntime(17722): at android.os.Handler.dispatchMessage(Handler.java:92)
01-21 21:40:57.885: E/AndroidRuntime(17722): at android.os.Looper.loop(Looper.java:137)
01-21 21:40:57.885: E/AndroidRuntime(17722): at android.app.ActivityThread.main(ActivityThread.java:5419)
01-21 21:40:57.885: E/AndroidRuntime(17722): at java.lang.reflect.Method.invokeNative(Native Method)
01-21 21:40:57.885: E/AndroidRuntime(17722): at java.lang.reflect.Method.invoke(Method.java:525)
01-21 21:40:57.885: E/AndroidRuntime(17722): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1187)
01-21 21:40:57.885: E/AndroidRuntime(17722): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1003)
01-21 21:40:57.885: E/AndroidRuntime(17722): at dalvik.system.NativeStart.main(Native Method)
01-21 21:45:57.988: I/Process(17722): Sending signal. PID: 17722 SIG: 9
答案 0 :(得分：1)
你应该将你的网络代码包装在后台线程或AsyncTask类中，因为在android中不允许主线程中的网络操作。
例如，您的异步任务代码应如下所示
private class LongOperation extends AsyncTask<String, Void, String> {
@Override
protected String doInBackground(String... params) {
try {
client = new Socket("127.0.0.1", 4444); //connect to server
printwriter = new PrintWriter(client.getOutputStream(), true);
printwriter.write(messsage); //write the message to output stream
printwriter.flush();
printwriter.close();
client.close(); //closing the connection
} catch (UnknownHostException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
return "Executed";
}
@Override
protected void onPostExecute(String result) {
TextView txt = (TextView) findViewById(R.id.output);
txt.setText("Executed"); // txt.setText(result);
// might want to change "executed" for the returned string passed
// into onPostExecute() but that is upto you
}
@Override
protected void onPreExecute() {}
@Override
protected void onProgressUpdate(Void... values) {}
}
并启动异步任务将如下所示
package com.example.simpleclient;
import java.io.IOException;
import java.io.PrintWriter;
import java.net.Socket;
import java.net.UnknownHostException;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
public class SimpleClientActivity extends Activity {
private Socket client;
private PrintWriter printwriter;
private EditText textField;
private Button button;
private String messsage;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
textField = (EditText) findViewById(R.id.editText1); //reference to the text field
button = (Button) findViewById(R.id.button1); //reference to the send button
//Button press event listener
button.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
messsage = textField.getText().toString(); //get the text message on the text field
textField.setText(""); //Reset the text field to blank
new LongOperation().execute("");
});
}
}
您可以在活动中定义异步任务