在運行AsyncTask時得到運行時異常

-1

我得到Exception在Runtime與AsyncTask類。但是我無法準確地確定在發生這種情況時在BufferReader while循環中的位置。我可以在調試器中看到讀取文件的第一行，然後在設備上讀取第二行，但是我認爲在創建節點對象或更新進度的這一點是拋出Exception時。任何幫助表示讚賞。在運行AsyncTask時得到運行時異常

package com.example.george.droidscanner; 

import android.os.AsyncTask; 
import android.os.Bundle; 
import android.support.v7.app.AppCompatActivity; 
import android.view.View; 
import android.widget.ArrayAdapter; 
import android.widget.Button; 
import android.widget.ListView; 
import android.widget.TextView; 

import java.io.BufferedReader; 
import java.io.FileNotFoundException; 
import java.io.FileReader; 
import java.io.IOException; 
import java.net.InetAddress; 
import java.net.UnknownHostException; 
import java.util.ArrayList; 

public class MainActivity extends AppCompatActivity { 

    Button btnRead; 
    TextView textResult; 

    ListView listViewNode; 
    ArrayList<Node> listNote; 
    ArrayAdapter<Node> adapter; 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_main); 
     btnRead = (Button)findViewById(R.id.readclient); 
     textResult = (TextView)findViewById(R.id.result); 

     listViewNode = (ListView)findViewById(R.id.nodelist); 
     listNote = new ArrayList<>(); 
     ArrayAdapter<Node> adapter = new ArrayAdapter<Node>(
         MainActivity.this, 
         android.R.layout.simple_list_item_1, 
         listNote); 
     listViewNode.setAdapter(adapter); 

     btnRead.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View v) { 
       new TaskReadAddresses(listNote, listViewNode).execute(); 
      } 
     }); 
    } 


    private class TaskReadAddresses extends AsyncTask<Void, Node, Void> { 

     ArrayList<Node> array; 
     ListView listView; 

     TaskReadAddresses(ArrayList<Node> array, ListView v){ 
      listView = v; 
      this.array = array; 
      array.clear(); 
      textResult.setText("querying..."); 
     } 

     @Override 
     protected Void doInBackground(Void... params) { 
      readAddresses(); 
      return null; 
     } 

     @Override 
     protected void onPostExecute(Void aVoid) { 
      textResult.setText("Done"); 
     } 

     @Override 
     protected void onProgressUpdate(Node... values) { 
      listNote.add(values[0]); 
      ((ArrayAdapter)(listView.getAdapter())).notifyDataSetChanged(); 
     } 

     private void readAddresses() { 
      BufferedReader bufferedReader = null; 

      try { 
       bufferedReader = new BufferedReader(new FileReader("/proc/net/arp")); 

       String line; 
       while ((line = bufferedReader.readLine()) != null) { 
        String[] splitted = line.split(" +"); 
        if (splitted != null && splitted.length >= 4) { 
         String ip = splitted[0]; 
         String mac = splitted[3]; 
         if (mac.matches("..:..:..:..:..:..")) { 
          Node thisNode = new Node(ip, mac); 
          publishProgress(thisNode); 
         } 
        } 
       } 

      } catch (FileNotFoundException e) { 
       e.printStackTrace(); 
      } catch (IOException e) { 
       e.printStackTrace(); 
      } finally{ 
       try { 
        bufferedReader.close(); 
       } catch (IOException e) { 
        e.printStackTrace(); 
       } 
      } 
     } 
    } 
}

節點類

package com.example.george.droidscanner; 

import java.io.IOException; 
import java.net.InetAddress; 
import java.net.UnknownHostException; 

/** 
* Created by george on 2/14/17. 
*/ 

public class Node { 
    String ip; 
    String mac; 
    String CanonicalHostName; 
    String HostName; 
    String LocalHostCanonicalHostName; 
    String LocalHostHostName; 
    String remark; 
    boolean isReachable; 

    Node(String ip, String mac){ 
     this.ip = ip; 
     this.mac = mac; 
     queryHost(); 
    } 

    @Override 
    public String toString() { 
     return "IP: " + ip + "\n" + 
       "MAC: " + mac + "\n" + 
       "CanonicalHostName:\t" + CanonicalHostName + "\n" + 
       "HostName:\t" + HostName + "\n" + 
       "getLocalHost().getCanonicalHostName():\t" + LocalHostCanonicalHostName + "\n" + 
       "getLocalHost().getHostName():\t" + LocalHostHostName + "\n" + 
       "isReachable: " + isReachable + 
       "\n" + remark; 
    } 

    private void queryHost(){ 
     try { 
      InetAddress inetAddress = InetAddress.getByName(ip); 
      CanonicalHostName = inetAddress.getCanonicalHostName(); 
      HostName = inetAddress.getHostName(); 
      LocalHostCanonicalHostName = inetAddress.getLocalHost().getCanonicalHostName(); 
      LocalHostHostName = inetAddress.getLocalHost().getHostName(); 
      isReachable = inetAddress.isReachable(3000); 

     } catch (UnknownHostException e) { 
      e.printStackTrace(); 
      remark = e.getMessage(); 
     } catch (IOException e) { 
      e.printStackTrace(); 
      remark = e.getMessage(); 
     } 
    } 
}

XML文件

<?xml version="1.0" encoding="utf-8"?> 
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    xmlns:tools="http://schemas.android.com/tools" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent" 
    android:padding="16dp" 
    android:orientation="vertical" 
    tools:context="com.example.george.droidscanner.MainActivity"> 


    <TextView 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:layout_gravity="center_horizontal" 
     android:autoLink="web" 
     android:text="http://android-er.blogspot.com/" 
     android:textStyle="bold" /> 

    <Button 
     android:id="@+id/readclient" 
     android:layout_width="match_parent" 
     android:layout_height="wrap_content" 
     android:textAllCaps="false" 
     android:text="Read Ip/MAC addresses"/> 

    <TextView 
     android:id="@+id/result" 
     android:layout_width="match_parent" 
     android:layout_height="wrap_content" 
     android:typeface="monospace" 
     android:textSize="24sp"/> 

    <ListView 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:id="@+id/nodelist"> 

    </ListView> 

</LinearLayout>

運行時異常錯誤

E/AndroidRuntime: FATAL EXCEPTION: AsyncTask #1 
        Process: com.example.george.droidscanner, PID: 18522 
        java.lang.RuntimeException: An error occured while executing doInBackground() 
         at android.os.AsyncTask$3.done(AsyncTask.java:304) 
         at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:355) 
         at java.util.concurrent.FutureTask.setException(FutureTask.java:222) 
         at java.util.concurrent.FutureTask.run(FutureTask.java:242) 
         at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231) 
         at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112) 
         at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587) 
         at java.lang.Thread.run(Thread.java:818) 
        Caused by: java.lang.SecurityException: Permission denied (missing INTERNET permission?) 
         at java.net.InetAddress.lookupHostByName(InetAddress.java:451) 
         at java.net.InetAddress.getLocalHost(InetAddress.java:396) 
         at com.example.george.droidscanner.Node.queryHost(Node.java:44) 
         at com.example.george.droidscanner.Node.<init>(Node.java:24) 
         at com.example.george.droidscanner.MainActivity$TaskReadAddresses.readAddresses(MainActivity.java:95) 
         at com.example.george.droidscanner.MainActivity$TaskReadAddresses.doInBackground(MainActivity.java:67) 
         at com.example.george.droidscanner.MainActivity$TaskReadAddresses.doInBackground(MainActivity.java:53) 
         at android.os.AsyncTask$2.call(AsyncTask.java:292) 
         at java.util.concurrent.FutureTask.run(FutureTask.java:237) 
         at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)  
         at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)  
         at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)  
         at java.lang.Thread.run(Thread.java:818)  
        Caused by: android.system.GaiException: android_getaddrinfo failed: EAI_NODATA (No address associated with hostname) 
         at libcore.io.Posix.android_getaddrinfo(Native Method) 
         at libcore.io.ForwardingOs.android_getaddrinfo(ForwardingOs.java:55) 
         at java.net.InetAddress.lookupHostByName(InetAddress.java:438) 
         at java.net.InetAddress.getLocalHost(InetAddress.java:396)  
         at com.example.george.droidscanner.Node.queryHost(Node.java:44)  
         at com.example.george.droidscanner.Node.<init>(Node.java:24)  
         at com.example.george.droidscanner.MainActivity$TaskReadAddresses.readAddresses(MainActivity.java:95)  
         at com.example.george.droidscanner.MainActivity$TaskReadAddresses.doInBackground(MainActivity.java:67)  
         at com.example.george.droidscanner.MainActivity$TaskReadAddresses.doInBackground(MainActivity.java:53)  
         at android.os.AsyncTask$2.call(AsyncTask.java:292)  
         at java.util.concurrent.FutureTask.run(FutureTask.java:237)  
         at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)  
         at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)  
         at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)  
         at java.lang.Thread.run(Thread.java:818)

來源

2017-02-15 miatech

在清單中添加此行：

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

來源

2017-02-15 17:40:45

這是問題之一，但不是主要問題。注意在那之前有一個例外。你是否運行它並且工作？...因爲我剛剛添加了權限並仍然有例外 – miatech

我的不好，我在錯誤的地方添加了權限...謝謝 – miatech

正如您在日誌中看到的那樣。它是由原因

Caused by: java.lang.SecurityException: Permission denied (missing INTERNET permission?)

添加以下權限AndroidManifest

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

來源

2017-02-15 17:41:00 Sanjeet

在那之前還有其他異常... – miatech

我的不好，我在錯誤的地方添加了許可......謝謝 – miatech

在運行AsyncTask時得到運行時異常

回答

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