在安卓设备上接收/阅读邮件

Question

在安卓设备上接收/阅读邮件

javaandroidemail

4

我是新手，想要构建一个应用程序来接收和阅读自己应用程序中的电子邮件。我参考了这些链接和一些博客来帮助编写代码。使用POP3协议使用JavaMail检索所有未读电子邮件

https://buddhimawijeweera.wordpress.com/2011/02/09/sendreceiveemailsjava/

https://metoojava.wordpress.com/2010/03/21/java-code-to-receive-mail-using-javamailapi/

我已经工作了将近两周，但是应用程序仍然不能显示收到的电子邮件。请帮助我找到错误。或者，您是否知道一种连接 Gmail 应用程序与我的应用程序以接收电子邮件的代码？非常感谢您对该应用程序的任何帮助。

MailReaderActivity.java（主要活动）

public class MailReaderActivity extends Activity{

    Folder inbox;


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

        StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
        StrictMode.setThreadPolicy(policy);


    }

    public MailReaderActivity(){

        Properties props = System.getProperties();
        props.setProperty("mail.store.protocol", "imaps");
        try {

            Session session = Session.getDefaultInstance(props, null);
            Store store;
            store = session.getStore("imaps");
            store.connect("imap.gmail.com","<user@gmail.com>","<password>");

            inbox = store.getFolder("Inbox");
            System.out.println("No of Unread Messages : " + inbox.getUnreadMessageCount());

            inbox.open(Folder.READ_ONLY);

            Message messages[] = inbox.search(new FlagTerm(new Flags(Flag.SEEN), false));

            FetchProfile fp = new FetchProfile();
            fp.add(FetchProfile.Item.ENVELOPE);
            fp.add(FetchProfile.Item.CONTENT_INFO);
            inbox.fetch(messages, fp);

            try {
                printAllMessages(messages);
                inbox.close(true);
                store.close();
            } catch (Exception ex) {
                System.out.println("Exception arise at the time of read mail");
                ex.printStackTrace();
            }
        } catch (NoSuchProviderException e) {
            e.printStackTrace();
            System.exit(1);
        } catch (MessagingException e) {
            e.printStackTrace();
            System.exit(2);
        }
    }


    public void printAllMessages(Message[] msgs) throws Exception
    {
        for (int i = 0; i < msgs.length; i++)
        {
            System.out.println("MESSAGE #" + (i + 1) + ":");
            printEnvelope(msgs[i]);
        }
    }
    public void printEnvelope(Message message) throws Exception
    {
        Address[] a;
        // FROM
        if ((a = message.getFrom()) != null)
        {
            for (int j = 0; j < 2; j++)
            {
                System.out.println("FROM: " + a[j].toString());
            }
        }
        // TO
        if ((a = message.getRecipients(Message.RecipientType.TO)) != null)
        {
            for (int j = 0; j < 2; j++)
            {
                System.out.println("TO: " + a[j].toString());
            }
        }
        String subject = message.getSubject();
        Date receivedDate = message.getReceivedDate();
        String content = message.getContent().toString();
        System.out.println("Subject : " + subject);
        System.out.println("Received Date : " + receivedDate.toString());
        System.out.println("Content : " + content);
        getContent(message);
    }

    public void getContent(Message msg)
    {
        try
        {
            String contentType = msg.getContentType();
            System.out.println("Content Type : " + contentType);
            Multipart mp = (Multipart) msg.getContent();
            int count = mp.getCount();
            for (int i = 0; i < count; i++)
            {
                dumpPart(mp.getBodyPart(i));
            }
        }
        catch (Exception ex)
        {
            System.out.println("Exception arise at get Content");
            ex.printStackTrace();
        }
    }

    public void dumpPart(Part p) throws Exception
    {
        // Dump input stream ..
        InputStream is = p.getInputStream();
        // If "is" is not already buffered, wrap a BufferedInputStream
        // around it.
        if (!(is instanceof BufferedInputStream))
        {
            is = new BufferedInputStream(is);
        }
        int c;
        System.out.println("Message : ");
        while ((c = is.read()) != -1)
        {
            System.out.write(c);
        }
    }

    public static void main(String args[])
    {
        new MailReaderActivity();
    }
}

Manifest.xml

<?xml version="1.0" encoding="utf-8"?>

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


<application
    android:allowBackup="true"
    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name"
    android:theme="@style/AppTheme" >
    <activity
        android:name=".MailReaderActivity"
        android:label="@string/app_name" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

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

Logcat

 //01-19 13:09:00.554    8487-8487/com.example.dell.frfr E/Trace﹕ error opening trace file: No such file or directory (2)
01-19 13:09:00.812    8487-8487/com.example.dell.frfr E/AndroidRuntime﹕ FATAL EXCEPTION: main
    java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.dell.frfr/com.example.dell.frfr.MailReaderActivity}: android.os.NetworkOnMainThreadException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2277)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2403)
at android.app.ActivityThread.access$600(ActivityThread.java:165)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1373)
at android.os.Handler.dispatchMessage(Handler.java:107)
at android.os.Looper.loop(Looper.java:194)
at android.app.ActivityThread.main(ActivityThread.java:5370)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:525)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:833)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600)
at dalvik.system.NativeStart.main(Native Method)
     Caused by: android.os.NetworkOnMainThreadException
at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1128)
            at java.net.InetAddress.lookupHostByName(InetAddress.java:385)
            at java.net.InetAddress.getAllByNameImpl(InetAddress.java:236)
            at java.net.InetAddress.getByName(InetAddress.java:289)
            at java.net.InetSocketAddress.<init>(InetSocketAddress.java:105)
            at java.net.InetSocketAddress.<init>(InetSocketAddress.java:90)
            at com.sun.mail.util.SocketFetcher.createSocket(SocketFetcher.java:321)
            at com.sun.mail.util.SocketFetcher.getSocket(SocketFetcher.java:237)
            at com.sun.mail.iap.Protocol.<init>(Protocol.java:116)
            at com.sun.mail.imap.protocol.IMAPProtocol.<init>(IMAPProtocol.java:115)
            at com.sun.mail.imap.IMAPStore.newIMAPProtocol(IMAPStore.java:685)
            at com.sun.mail.imap.IMAPStore.protocolConnect(IMAPStore.java:636)
            at javax.mail.Service.connect(Service.java:295)
            at javax.mail.Service.connect(Service.java:176)
            at com.example.dell.frfr.MailReaderActivity.<init>(MailReaderActivity.java:53)
            at java.lang.Class.newInstanceImpl(Native Method)
            at java.lang.Class.newInstance(Class.java:1319)
            at android.app.Instrumentation.newActivity(Instrumentation.java:1123)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2268)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2403)
            at android.app.ActivityThread.access$600(ActivityThread.java:165)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1373)
            at android.os.Handler.dispatchMessage(Handler.java:107)
            at android.os.Looper.loop(Looper.java:194)
            at android.app.ActivityThread.main(ActivityThread.java:5370)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:525)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:833)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600)
            at dalvik.system.NativeStart.main(Native Method)
//

- ini

你能否贴出你的日志(logcat)? - Milad Faridnia

StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build(); StrictMode.setThreadPolicy(policy); <-- 在调用构造函数之前应该先调用这两行代码。尝试在onCreate()方法中添加这两行代码后再调用构造函数的内容。 - Malintha

感谢您的帮助。现在不再显示“NetworkOnMailThread”异常，但仍然无法显示邮件。调试输出如下： DEBUG IMAPS：尝试连接到主机“imap.gmail.com”，端口993，isSSL true我们认为问题在于连接帐户。我们是否需要在代码中进行任何更改？ - ini

2个回答

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可以查看英文原文，
原文链接

- CrazyWolf132 · Answer 1

我不知道你是否已经解决了这个错误，但如果我仍然回答它，可能有类似问题的人会受益。

在您的LogCat中，它显示“Caused by: android.os.NetworkOnMainThreadException” Android默认情况下不允许任何网络与应用程序的其余部分在同一线程上运行。因此，为了解决这个问题，我们只需要简单地创建一个新线程来运行它。

替换：

public static void main(String args[])
    {
        new MailReaderActivity();
    }

使用这个：

public static void main(String args[])
{
  Thread thread = new Thread() {
      @Override
      public void run() {
          new MailReaderActivity();
      }
  };

  thread.start();
}

- Tarik Weiss · Answer 2

你应该使用AsyncTask异步执行网络线程。欲了解更多信息，请阅读文档。