Question

我一直在为我的同事制作一个销售应用程序。我一直在做一个步骤，通过制作一个服务器应用程序，在我的计算机上读取一个txt文件，然后将其发送到Android手机上的应用程序，显示结果。问题是，一旦asyncTask完成，手机上的应用程序崩溃，服务器和手机应用程序都会终止。我查看了logcat，它似乎是一个nullpointer异常。我发现这很奇怪，因为我的代码中的while循环应该只允许非空数据通过。这是我的代码：

package com.AWSbeacon;

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.Socket;
import java.net.UnknownHostException;
import java.util.ArrayList;

import android.app.Activity;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;

import com.AWSbeacon.*;

public class MainActivity extends Activity{

    String[] Names = null;
    ArrayList<String> names = new ArrayList<String>();


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Button starter = (Button) this.findViewById(R.id.button1);
        starter.setOnClickListener(new OnClickListener(){

            @Override
            public void onClick(View v) {
            new GetNames().execute();
            Names = names.toArray(Names); //the error pops up here  
            for(int i=0; i<Names.length; i++){
                TextView txtView1 = (TextView)findViewById((int) R.id.text1);
                txtView1.setText((CharSequence)txtView1 + Names[i]);
            }
            }
            });
        }

 class GetNames extends AsyncTask<Void,Void,Void>{


        ArrayList<String> names = new ArrayList<String>();
        String[] Names = null;
        DataOutputStream out = null;
        DataInputStream in = null;
                Socket sock = null;
            String  T = null;

    @Override
    protected Void doInBackground(Void... params) {

                try {
                    sock = new Socket("elvishknight1.noip.me", 8000);
                } catch (UnknownHostException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }

                try {
                    in = new DataInputStream(sock.getInputStream());
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
                try {
                 out = new DataOutputStream(sock.getOutputStream());
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }

            try {
                while(true){
                out.writeUTF("ok");
                T = in.readUTF();
                if(in!=null && !in.readUTF().contains("end")){
                names.add(T);
                }
                else if(in.readUTF().contains("end")){
                    break;
                }
            }

                out.flush();
                out.close();
                in.close();
                sock.close();


            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
                return null; 

        }
    }

我的服务器代码（以防万一）：

package beaconserver;

import java.io.*;


import java.net.*;
import java.util.*;

public class Bserver {

 static BufferedReader text = null; 
 static ServerSocket Sock = null;
 static Socket server = null;

    public static void main(String[] args) {

        ArrayList<String> Names = new ArrayList<String>();

    try {
        text = new BufferedReader(new FileReader("/home/kyle/Documents/names.txt"));
    } catch (FileNotFoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
     try {

        String names = text.readLine();
        while((names=text.readLine())!=null){
          Names.add(names);
        }
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
     String[] Text = new String[Names.size()];
     Text = Names.toArray(Text);
        SendMessage(Text);
    }

    public static void SendMessage(String[] lines){
        DataInputStream in = null;
        DataOutputStream out = null;
        String ok = null;
        try {
            Sock = new ServerSocket(8000);
        } catch (IOException e) {
            e.printStackTrace();
        }
        try{
            server = Sock.accept();
                in = new DataInputStream(server.getInputStream());
                out = new DataOutputStream(server.getOutputStream());

                for(int i=0; i<lines.length; i++){
                    while(ok==null){
                     ok = in.readUTF();
                        if(ok!=null){
                            break;
                        }
                    }
                    out.writeUTF(lines[i]);
                }
                out.writeUTF("end");
            in.close();
            out.flush();
            out.close();
            server.close();
            Sock.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

以及logcat：

05-25 09:23:37.218: E/AndroidRuntime(9722): FATAL EXCEPTION: main
05-25 09:23:37.218: E/AndroidRuntime(9722): java.lang.NullPointerException
05-25 09:23:37.218: E/AndroidRuntime(9722):     at java.util.ArrayList.toArray(ArrayList.java:514)
05-25 09:23:37.218: E/AndroidRuntime(9722):     at com.AWSbeacon.MainActivity$1.onClick(MainActivity.java:37)
05-25 09:23:37.218: E/AndroidRuntime(9722):     at android.view.View.performClick(View.java:4202)
05-25 09:23:37.218: E/AndroidRuntime(9722):     at android.view.View$PerformClick.run(View.java:17340)
05-25 09:23:37.218: E/AndroidRuntime(9722):     at android.os.Handler.handleCallback(Handler.java:725)
05-25 09:23:37.218: E/AndroidRuntime(9722):     at android.os.Handler.dispatchMessage(Handler.java:92)
05-25 09:23:37.218: E/AndroidRuntime(9722):     at android.os.Looper.loop(Looper.java:137)
05-25 09:23:37.218: E/AndroidRuntime(9722):     at android.app.ActivityThread.main(ActivityThread.java:5039)
05-25 09:23:37.218: E/AndroidRuntime(9722):     at java.lang.reflect.Method.invokeNative(Native Method)
05-25 09:23:37.218: E/AndroidRuntime(9722):     at java.lang.reflect.Method.invoke(Method.java:511)
05-25 09:23:37.218: E/AndroidRuntime(9722):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
05-25 09:23:37.218: E/AndroidRuntime(9722):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
05-25 09:23:37.218: E/AndroidRuntime(9722):     at dalvik.system.NativeStart.main(Native Method)

提前感谢您的帮助

Answer 1

您在tour onClickListener中使用了错误的名称变量。也许您应该考虑重命名一些变量，例如使用nameArray

不幸的是App在使用AsyncTask时已经停止了

1 个答案: