问题
I used javamail to send email in android. But it throws the Exception NetworkOnMainThreadException. How to solve this exception?
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("mail@gmail.com", "pwd");
}
public void sendEmail(View view){
String[] toArr = {"samp@gmail.com"};
m.setTo(toArr);
m.setFrom("mail613@gmail.com");
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 …..
} `
回答1:
You need to use an AsyncTask to do all your network operations.
Your network operation can take a lot of time and the UI would get unresponsive if it is done on the main UI thread. And if your UI freezes for a long time, the app might get killed by the OS.
Thus Android 4+ makes it mandatory to use a background thread to perform network operations.
Put the code to do the network activity inside doInBacground() and all the AsyncTask using execute().
Here is how your AsyncTask would look like :
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
}
}
And you can call it anywhere using new SendMail().execute("");
回答2:
You are trying to access the network on your UI thread. This is bad because it will freeze the UI until the network response has returned. You should do this network access on a separate thread.
There are many options, but the simplest option would be:
- Convert msg in
MimeMessage msg = new MimeMessage(session);to befinal. - Wrap
Transport.send(msg);asnew Thread(new Runnable() { @Override public void run() { Transport.send(msg); } }).start();
You can equally use an AsyncTask which will allow you to update the UI after in onPostExecute (or you can get this behaviour by creating a Handler on the UI thread and post()ing to it.
回答3:
Don't do network tasks on the main thread. Use an AsyncTask
回答4:
This problem you can find if you will search it as Raghav told in comment.But just some basic explanation,If you do any network(internet) related task in your app,then prefer to do in any other thread rather than in Main UIThread.So you can go for Asynctask or Service.If the task is leangthy then Service is better else you can go for Asyntask.HTH :)
来源：https://stackoverflow.com/questions/15188810/how-to-solve-networkonmainthreadexception-error-in-android