android服务 - 打开套接字抛出空异常

Question

我正在尝试创建远程服务来处理几个不同应用程序的所有客户端-服务器通信。主要思想是从主要 Activity 启动服务并打开到服务器的通信套接字。之后，套接字将被其他应用程序使用——这就是为什么我想为它使用远程服务……

现在我的套接字连接出现问题，它在我的设备上抛出 null 异常。它在使用旧版 Android 的 AVD 上运行良好。

这是我的部分代码:

我的主要 Activity :

final ServiceConnection conn = new ServiceConnection() {
        public void onServiceConnected(ComponentName name, IBinder service) {
            myRemoteService = ConnectionInterface.Stub.asInterface(service);
        }
        public void onServiceDisconnected(ComponentName name) {
            myRemoteService = null;
        }
    };

    final Thread t = new Thread(){
        public void run(){
            bindService(new Intent(getApplicationContext(), ConnectionRemoteService.class),conn,Context.BIND_AUTO_CREATE);
            while(true){}
        }

   };

稍后我用 t.start() 启动线程 t;

我的连接远程服务:

package com.mainlauncher;

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.Socket;
import java.net.UnknownHostException;
import java.util.ResourceBundle;
import android.app.Service;
import android.content.Context;
import android.content.Intent;
import android.net.wifi.WifiManager;
import android.os.IBinder;
import android.widget.Toast;

public class ConnectionRemoteService extends Service {

private static final int SERVERPORT = 7777;
private static final String SERVERADDRESS = "192.168.1.106";

private String deviceID;
private Socket socket;
private DataInputStream in;
private DataOutputStream out;

@Override
public void onCreate() {
    super.onCreate();
    WifiManager wm = (WifiManager)getSystemService(Context.WIFI_SERVICE);
    deviceID = wm.getConnectionInfo().getMacAddress();
    Toast.makeText(this, "Service On.", Toast.LENGTH_LONG).show();
    open();
}

@Override
public void onDestroy() {
    Toast.makeText(this, "Service Off.", Toast.LENGTH_LONG).show();
    close();
}

@Override
public IBinder onBind(Intent intent) {
    return myRemoteServiceStub;
}   

private ConnectionInterface.Stub myRemoteServiceStub = new ConnectionInterface.Stub() {

};

void open(){
    try{
        socket = new Socket(SERVERADDRESS,SERVERPORT);
        in = new DataInputStream(socket.getInputStream());
        out = new DataOutputStream(socket.getOutputStream());
        out.writeUTF(deviceID);
    }
    catch(Exception  e){
        System.err.println(e.getMessage());
    }
}

void close(){
    try {
        if(in!=null)
            in.close();
        if(out!=null)
            out.close();
        if(socket!=null)
            socket.close();
    } 
    catch(Exception  e){
        System.err.println(e.getMessage());
    }
    socket=null;

}

}

主要 list 文件:

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.mainlauncher"
android:versionCode="1"
android:versionName="1.0" >

<uses-sdk
    android:minSdkVersion="8"
    android:targetSdkVersion="15" />

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

<application
    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name" >
    <activity android:name=".MainLauncherWindow" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>

    <service
        android:name=".ConnectionRemoteService"
        android:process=":remote"/>
</application>

这里是 DDMS 根据要求在“调试”模式下登录:

11-06 12:13:45.130: D/InputDispatcher(392): notifyMotion - eventTime=4210399491000, deviceId=6, source=0x1002, policyFlags=0x0, action=0x0, flags=0x0, metaState=0x0, buttonState=0x0, edgeFlags=0x0, xPrecision=1.529167, yPrecision=1.383594, downTime=4210399491000 11-06 12:13:45.130: D/InputDispatcher(392): Pointer 0: id=0, toolType=1, x=66.049042, y=492.196503, pressure=0.233333, size=0.250980, touchMajor=44.054604, touchMinor=44.054604, toolMajor=4.818472, toolMinor=4.818472, orientation=0.000000 11-06 12:13:45.130: D/InputDispatcher(392): Dispatch MotionEvent [action=0] ToCurrentInputTarget: 40f9a6a8 com.mainlauncher/com.mainlauncher.MainLauncherWindow (server) 11-06 12:13:45.150: D/PowerManagerService(392): setPowerState: mPowerState=0x3, newState=0x3, noChangeLights=false, reason=3, force=false, mProximitySensorActive=false, mBootCompleted=true, mUseSoftwareAutoBrightness=true (repeat:1) 11-06 12:13:45.160: D/PowerManagerService(392): setPowerState: mPowerState=0x3, newState=0x3, noChangeLights=false, reason=2, force=false, mProximitySensorActive=false, mBootCompleted=true, mUseSoftwareAutoBrightness=true 11-06 12:13:45.160: I/PowerManagerService-JNI(392): [Stability] PowerManagerService_userActivity JNI pass power key event to PowerManagerService userActivity() 11-06 12:13:45.160: D/PowerManagerService(392): setTimeoutLocked: now=4210399, timeoutOverride=-1, nextState=0x3, when=4216399 (mKeylightDelay=6000, mDimDelay=2147469000, mScreenOffDelay=7000) 11-06 12:13:45.190: D/InputDispatcher(392): notifyMotion - eventTime=4210464940000, deviceId=6, source=0x1002, policyFlags=0x0, action=0x1, flags=0x0, metaState=0x0, buttonState=0x0, edgeFlags=0x0, xPrecision=1.529167, yPrecision=1.383594, downTime=4210399491000 11-06 12:13:45.190: D/InputDispatcher(392): Pointer 0: id=0, toolType=1, x=65.395096, y=492.919250, pressure=0.233333, size=0.219608, touchMajor=38.547779, touchMinor=38.547779, toolMajor=4.818472, toolMinor=4.818472, orientation=0.000000 11-06 12:13:45.190: D/InputDispatcher(392): Dispatch MotionEvent [action=1] ToCurrentInputTarget: 40f9a6a8 com.mainlauncher/com.mainlauncher.MainLauncherWindow (server) 11-06 12:13:45.220: D/dalvikvm(153): Before fork 11-06 12:13:45.230: D/dalvikvm(20210): Fork pid: 0 11-06 12:13:45.230: D/dalvikvm(20210): Late-enabling CheckJNI 11-06 12:13:45.230: D/dalvikvm(153): Fork pid: 20210 11-06 12:13:45.240: D/Performance(392): AutoProf Starting process { Process=com.mainlauncher:remote, ActivityName=com.mainlauncher/.ConnectionRemoteService}, pid=20210 11-06 12:13:45.240: I/ActivityManager(392): Start proc com.mainlauncher:remote for service com.mainlauncher/.ConnectionRemoteService: pid=20210 uid=10080 gids={3003} 11-06 12:13:45.300: D/ConnSrv_Debug(392): get mDefaultProxy null by 20210/10080 11-06 12:13:45.300: D/WifiStateMachine(392): syncRequestConnectionInfo mWifiInfo=SSID: linksys, BSSID: 00:14:bf:e6:13:8f, MAC: 18:87:96:88:cd:68, Supplicant state: COMPLETED, RSSI: -83, Link speed: 36, Frequency: 2462, Net ID: 1, Explicit connect: false 11-06 12:13:45.320: D/AndroidRuntime(20210): Shutting down VM 11-06 12:13:45.320: W/dalvikvm(20210): threadid=1: thread exiting with uncaught exception (group=0x40a6b228) 11-06 12:13:45.320: E/EmbeddedLogger(392): App crashed! Process: com.mainlauncher:remote 11-06 12:13:45.320: E/EmbeddedLogger(392): App crashed! Package: com.mainlauncher v1 (1.0) 11-06 12:13:45.320: E/AndroidRuntime(20210): FATAL EXCEPTION: main 11-06 12:13:45.320: E/AndroidRuntime(20210): java.lang.RuntimeException: Unable to create service com.mainlauncher.ConnectionRemoteService: java.lang.NullPointerException 11-06 12:13:45.320: E/AndroidRuntime(20210): at android.app.ActivityThread.handleCreateService(ActivityThread.java:2593) 11-06 12:13:45.320: E/AndroidRuntime(20210): at android.app.ActivityThread.access$1600(ActivityThread.java:139) 11-06 12:13:45.320: E/AndroidRuntime(20210): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1326) 11-06 12:13:45.320: E/AndroidRuntime(20210): at android.os.Handler.dispatchMessage(Handler.java:99) 11-06 12:13:45.320: E/AndroidRuntime(20210): at android.os.Looper.loop(Looper.java:156) 11-06 12:13:45.320: E/AndroidRuntime(20210): at android.app.ActivityThread.main(ActivityThread.java:5025) 11-06 12:13:45.320: E/AndroidRuntime(20210): at java.lang.reflect.Method.invokeNative(Native Method) 11-06 12:13:45.320: E/AndroidRuntime(20210): at java.lang.reflect.Method.invoke(Method.java:511) 11-06 12:13:45.320: E/AndroidRuntime(20210): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784) 11-06 12:13:45.320: E/AndroidRuntime(20210): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551) 11-06 12:13:45.320: E/AndroidRuntime(20210): at dalvik.system.NativeStart.main(Native Method) 11-06 12:13:45.320: E/AndroidRuntime(20210): Caused by: java.lang.NullPointerException 11-06 12:13:45.320: E/AndroidRuntime(20210): at com.android.internal.os.LoggingPrintStream.println(LoggingPrintStream.java:298) 11-06 12:13:45.320: E/AndroidRuntime(20210): at com.mainlauncher.ConnectionRemoteService.open(ConnectionRemoteService.java:60) 11-06 12:13:45.320: E/AndroidRuntime(20210): at com.mainlauncher.ConnectionRemoteService.onCreate(ConnectionRemoteService.java:33) 11-06 12:13:45.320: E/AndroidRuntime(20210): at android.app.ActivityThread.handleCreateService(ActivityThread.java:2571) 11-06 12:13:45.320: E/AndroidRuntime(20210): ... 10 more 11-06 12:13:45.330: E/EmbeddedLogger(392): Application Label: Launcher

我在这一行得到异常:

socket = new Socket(SERVERADDRESS,SERVERPORT);

我知道很少有事情可以异常(exception):1.我用<uses-permission android:name="android.permission.INTERNET" />在我的主要 list 中。2.服务在分离线程下运行，而不是在主 Activity 线程上运行。3.没有防火墙等...4. 我已经检查了与服务器的连接(没有该服务一切正常)。5. 我也在 list 中使用 android:process=":remote"。

知道为什么会出现这种异常吗？我如何调试它以获得更多详细信息？

它在使用 OS 2.3 的 AVD 上可以找到，所以我认为它与主 Activity 线程异常有关，但我找不到原因。

谢谢，里奥兹。

Answer 1

您正在从 onCreate() 调用 open()。 onCreate() 在主线程上被调用。您不应该在主线程上执行网络 I/O。你在错误的地方得到了单独的线程。在您的 Activity 中，您正在启动一个单独的线程，该线程调用 bindService() 然后永远循环(无限循环消耗 CPU 周期，不是一件好事)。您不需要从单独的线程中调用 bindService()，因为 bindService() 是异步的。它只是启动绑定(bind)，实际上并不等待绑定(bind)完成。这可以在主线程上完成。

您需要启动线程的地方是在您的服务中。创建服务后，您应该在 onCreate() 中启动一个单独的线程，该单独的线程需要执行网络 I/O(即:打开套接字、读取、写入等)。

此外，您可以通过从 list 中删除 android:process=":remote" 来简化调试。这将使您能够更轻松地在服务方法中设置断点。