如何解決android中的NetworkOnMainThreadException錯誤？

我用javamail在android中發送郵件。但它會拋出異常NetworkOnMainThreadException。如何解決這個異常？如何解決android中的NetworkOnMainThreadException錯誤？

MainActivity

package com.aaa; 
import android.os.Bundle; 
import android.os.NetworkOnMainThreadException; 
import android.app.Activity; 
import android.util.Log; 
import android.view.Menu; 
import android.view.View; 
import android.widget.Toast; 

public class MainActivity extends Activity { 
private Mail m; 
@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_main); 
    m = new Mail("[email protected]", "pwd"); 
} 
public void sendEmail(View view){ 
     String[] toArr = {"[email protected]"}; 
     m.setTo(toArr); 
     m.setFrom("[email protected]"); 
     m.setSubject("subject"); 
     m.setBody("your message goes here"); 

     try { 
      //m.addAttachment("/sdcard/myPicture.jpg"); 
      if(m.send()) { 
       // success 
       Toast.makeText(MainActivity.this, "Email was sent successfully.", Toast.LENGTH_LONG).show(); 
      } else { 
       // failure 
       Toast.makeText(MainActivity.this, "Email was not sent.", Toast.LENGTH_LONG).show(); 
      } 
     } catch(Exception e) { 
      // some other problem 
      //Toast.makeText(MainActivity.this, "Email was not sent.", Toast.LENGTH_LONG).show(e); 
      Toast.makeText(MainActivity.this, ""+e+"", Toast.LENGTH_LONG).show(); 
      Log.e("SendMail",e.getMessage(),e); 
     } 

    } 

}

Mail.java

package com.aaa; 

import java.util.Date; 
import java.util.Properties; 
import javax.activation.CommandMap; 
import javax.activation.DataHandler; 
import javax.activation.DataSource; 
import javax.activation.FileDataSource; 
import javax.activation.MailcapCommandMap; 
import javax.mail.BodyPart; 
import javax.mail.Multipart; 
import javax.mail.PasswordAuthentication; 
import javax.mail.Session; 
import javax.mail.Transport; 
import javax.mail.internet.InternetAddress; 
import javax.mail.internet.MimeBodyPart; 
import javax.mail.internet.MimeMessage; 
import javax.mail.internet.MimeMultipart; 

public class Mail extends javax.mail.Authenticator { 
private String _user; 
private String _pass; 

private String[] _to; 
private String _from; 

private String _port; 
private String _sport; 

private String _host; 

private String _subject; 
private String _body; 

private boolean _auth; 

private boolean _debuggable; 

private Multipart _multipart; 


public Mail() { 
    _host = "smtp.gmail.com"; // default smtp server 
    _port = "465"; // default smtp port 
    _sport = "465"; // default socketfactory port 

    _user = ""; // username 
    _pass = ""; // password 
    _from = ""; // email sent from 
    _subject = ""; // email subject 
    _body = ""; // email body 

    _debuggable = false; // debug mode on or off - default off 
    _auth = true; // smtp authentication - default on 

    _multipart = new MimeMultipart(); 

    // There is something wrong with MailCap, javamail can not find a handler for the multipart/mixed part, so this bit needs to be added. 
    MailcapCommandMap mc = (MailcapCommandMap) CommandMap.getDefaultCommandMap(); 
    mc.addMailcap("text/html;; x-java-content-handler=com.sun.mail.handlers.text_html"); 
    mc.addMailcap("text/xml;; x-java-content-handler=com.sun.mail.handlers.text_xml"); 
    mc.addMailcap("text/plain;; x-java-content-handler=com.sun.mail.handlers.text_plain"); 
    mc.addMailcap("multipart/*;; x-java-content-handler=com.sun.mail.handlers.multipart_mixed"); 
    mc.addMailcap("message/rfc822;; x-java-content-handler=com.sun.mail.handlers.message_rfc822"); 
    CommandMap.setDefaultCommandMap(mc); 
} 

public Mail(String user, String pass) { 
    this(); 

    _user = user; 
    _pass = pass; 
} 

public boolean send() throws Exception { 
    Properties props = _setProperties(); 

    if(!_user.equals("") && !_pass.equals("") && _to.length > 0 && !_from.equals("") && !_subject.equals("") && !_body.equals("")) { 
     Session session = Session.getInstance(props, this); 

     MimeMessage msg = new MimeMessage(session); 

     msg.setFrom(new InternetAddress(_from)); 

     InternetAddress[] addressTo = new InternetAddress[_to.length]; 
     for (int i = 0; i < _to.length; i++) { 
      addressTo[i] = new InternetAddress(_to[i]); 
     } 
     msg.setRecipients(MimeMessage.RecipientType.TO, addressTo); 

     msg.setSubject(_subject); 
     msg.setSentDate(new Date()); 

     // setup message body 
     BodyPart messageBodyPart = new MimeBodyPart(); 
     messageBodyPart.setText(_body); 
     _multipart.addBodyPart(messageBodyPart); 

     // Put parts in message 
     msg.setContent(_multipart); 

     // send email 
     Transport.send(msg); 

     return true; 
    } else { 
     return false; 
    } 
} 

public void addAttachment(String filename) throws Exception { 
    BodyPart messageBodyPart = new MimeBodyPart(); 
    DataSource source = new FileDataSource(filename); 
    messageBodyPart.setDataHandler(new DataHandler(source)); 
    messageBodyPart.setFileName(filename); 

    _multipart.addBodyPart(messageBodyPart); 
} 

@Override 
public PasswordAuthentication getPasswordAuthentication() { 
    return new PasswordAuthentication(_user, _pass); 
} 

private Properties _setProperties() { 
    Properties props = new Properties(); 

    props.put("mail.smtp.host", _host); 

    if(_debuggable) { 
     props.put("mail.debug", "true"); 
    } 

    if(_auth) { 
     props.put("mail.smtp.auth", "true"); 
    } 

    props.put("mail.smtp.port", _port); 
    props.put("mail.smtp.socketFactory.port", _sport); 
    props.put("mail.smtp.socketFactory.class", "javax.net.ssl.SSLSocketFactory"); 
    props.put("mail.smtp.socketFactory.fallback", "false"); 

    return props; 
} 

// the getters and setters 
public String getBody() { 
    return _body; 
} 

public void setBody(String _body) { 
    this._body = _body; 
} 

public void setTo(String[] toArr) { 
    this._to = toArr; 
} 

public void setFrom(String string) { 
    this._from = string; 
} 

public void setSubject(String string) { 
    this._subject = string; 
} 

// more of the getters and setters ….. 
    } `

來源

2013-03-03 Ramki Anba

可以給電話我任何地方？ – 2013-03-03 18:01:59

http://android-developers.blogspot.co.uk/2009/05/painless-threading.html – Blundell 2013-03-03 18:03:23

[android.os.NetworkOnMainThreadException]（http：// stackoverflow。com/questions/6343166/android-os-networkonmainthreadexception） – Eric 2013-03-03 18:10:05

您需要使用AsyncTask做你的所有網絡操作。

您的網絡操作可能需要大量的時間和用戶界面將GE如果它在主UI線程上完成，則無響應。如果您的用戶界面長時間凍結，該應用可能會被操作系統殺死。

因此，Android 4+強制使用後臺線程來執行網絡操作。

把代碼做的網絡活動中doInBacground()和使用所有的AsyncTask。

這是你的AsyncTask會是什麼樣子：

private class SendMail extends AsyncTask<String, Integer, Void> { 
     protected void doInBackground() { 
        sendEmail(); 
 } 

 protected void onProgressUpdate() { 
    //called when the background task makes any progress 
 } 

  protected void onPreExecute() { 
     //called before doInBackground() is started 
 } 
 protected void onPostExecute() { 
     //called after doInBackground() has finished  
 } 
  }

而且你可以把它用new SendMail().execute("");

來源

2013-03-03 18:06:30 Swayam

不要在主線程中執行網絡任務。使用AsyncTask

來源

2013-03-03 18:01:01 MrChaz

這個問題，你可以找到，如果你將它作爲Raghav告訴comment.But只是一些基本的解釋，如果你在你的應用程序中做任何網絡（互聯網）相關的任務，那麼更喜歡做任何其他線程，而不是在主UIThread.So你可以去Asynctask或Service。如果任務是leangthy，那麼服務是更好的，否則你可以去Asyntask.HTH :)

來源

2013-03-03 18:01:38

您試圖訪問您的用戶界面上的網絡線。這很糟糕，因爲它會凍結UI，直到網絡響應返回。您應該在單獨的線程上執行此網絡訪問。

有多種選擇，但最簡單的辦法是：在MimeMessage msg = new MimeMessage(session);

轉換味精是final。
裹Transport.send(msg);作爲 new Thread(new Runnable() { @Override public void run() { Transport.send(msg); } }).start();

可以同樣使用AsyncTask，這將讓你更新UI在onPostExecute後（或者你可以在UI線程創建Handler和post()荷蘭國際集團獲得這個行爲它。

來源

2013-03-03 18:03:22 Dororo

如何解決android中的NetworkOnMainThreadException錯誤？

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