Lance nullPointerException et les plantages de l'application

Question

Ce code est mis en œuvre pour envoyer un courrier électronique à partir d'un client android et il se bloque constamment. Quand j'ai vérifié le journal des erreurs, il lit: J'ai essayé de dépanner pour voir d'où vient exactement cette erreur que je n'ai pas pu voir. Veuillez aider.

10-02 16:15:14.536 7493-7493/? E/AndroidRuntime﹕ FATAL EXCEPTION: main 
    Process: com.example.ken4ward.emailsender, PID: 7493 
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.ken4ward.emailsender/com.example.ken4ward.emailsender.MainActivity}: java.lang.NullPointerException 
      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195) 
      at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245) 
      at android.app.ActivityThread.access$800(ActivityThread.java:135) 
      at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196) 
      at android.os.Handler.dispatchMessage(Handler.java:102) 
      at android.os.Looper.loop(Looper.java:136) 
      at android.app.ActivityThread.main(ActivityThread.java:5021) 
      at java.lang.reflect.Method.invokeNative(Native Method) 
      at java.lang.reflect.Method.invoke(Method.java:515) 
      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:827) 
      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:643) 
      at dalvik.system.NativeStart.main(Native Method) 
    Caused by: java.lang.NullPointerException 
      at com.example.ken4ward.emailsender.MainActivity.onCreate(MainActivity.java:46) 
      at android.app.Activity.performCreate(Activity.java:5231) 
      at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1090) 
      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159) 
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245) 
            at android.app.ActivityThread.access$800(ActivityThread.java:135) 
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196) 
            at android.os.Handler.dispatchMessage(Handler.java:102) 
            at android.os.Looper.loop(Looper.java:136) 
            at android.app.ActivityThread.main(ActivityThread.java:5021) 
            at java.lang.reflect.Method.invokeNative(Native Method) 
            at java.lang.reflect.Method.invoke(Method.java:515) 
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:827) 
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:643) 
            at dalvik.system.NativeStart.main(Native Method) 

Ceci est le code.

import android.app.Activity; 
import android.app.ProgressDialog; 
import android.content.Context; 
import android.os.AsyncTask; 
import android.os.Bundle; 
import android.view.View; 
import android.widget.Button; 
import android.widget.EditText; 
import android.widget.Toast; 

import java.util.Properties; 

import javax.mail.Authenticator; 
import javax.mail.Message; 
import javax.mail.MessagingException; 
import javax.mail.PasswordAuthentication; 
import javax.mail.Session; 
import javax.mail.Transport; 
import javax.mail.internet.InternetAddress; 
import javax.mail.internet.MimeMessage; 

//import android.support.v7.app.AppCompatActivity; 

public class MainActivity extends Activity implements View.OnClickListener{ 

    EditText fieldEmail, emailSubject, emailBody; 
    String strFieldEmail, strEmailSubject, strEmailBody; 
    Button buttonLogin; 
    Context context = null ; 
    Session session = null; 
    ProgressDialog progressDialog; 

    @Override 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_main); 
     progressDialog = new ProgressDialog(MainActivity.this); 
     context = this; 

     fieldEmail = (EditText)this.findViewById(R.id.editEmail); 
     emailSubject = (EditText)this.findViewById(R.id.editSubject); 
     emailBody = (EditText)this.findViewById(R.id.editBody); 

     buttonLogin.setOnClickListener(this); 
    } 

    @Override 
    public void onClick(View v) { 
     strFieldEmail = fieldEmail.getText().toString(); 
     strEmailSubject = emailSubject.getText().toString(); 
     strEmailBody = emailBody.getText().toString(); 

     Properties properties = new Properties(); 
     properties.put("mail.smtp.host", "smtp.gmail.com"); 
     properties.put("mail.smtp.socketFactory.port", "465"); 
     properties.put("mail.smtp.socketFactory.class", "javax.net.ssl.SSLSocketFactory"); 
     properties.put("mail.smtp.auth", "true"); 
     properties.put("mail.smtp.port", "465"); 

     session = Session.getDefaultInstance(properties, new Authenticator() { 
      @Override 
      protected PasswordAuthentication getPasswordAuthentication() { 
       return new PasswordAuthentication("kehindeadeoya@gmail.com", "321g201115@...Ademnew"); 
      } 
     }); 
     progressDialog = ProgressDialog.show(context, "", "Sending email", true); 
     ReceivedFeedTask receivedFeedTask = new ReceivedFeedTask(); 
     receivedFeedTask.execute(); 
    } 

    class ReceivedFeedTask extends AsyncTask<String, Void, String> 
    { 
     @Override 
     protected String doInBackground(String... params) { 
      try 
      { 
       Message message = new MimeMessage(session); 
       message.setFrom(new InternetAddress("kehindeadeoya@gmail.com")); 
       message.setRecipients(Message.RecipientType.TO, InternetAddress.parse(strFieldEmail)); 
       message.setSubject(strEmailSubject); 
       message.setContent(strEmailBody, "text/html; charset=utf-8"); 
       Transport.send(message); 

      }catch (MessagingException messagingException) 
      { 
       messagingException.printStackTrace(); 
      }catch (Exception exception) 
      { 
       exception.printStackTrace(); 
      } 
      return null; 
     } 

     @Override 
     protected void onPostExecute(String result) 
     { 
      progressDialog.dismiss(); 
      fieldEmail.setText(""); 
      emailSubject.setText(""); 
      emailBody.setText(""); 
      Toast.makeText(getApplicationContext(), "Message sent", Toast.LENGTH_LONG).show(); 
     } 

    } 
} 

Answer 1

Vous devez ajouter l'activité dans votre fichier manifeste. Cela peut être un problème.

Answer 2

Il y a une erreur stupide que vous avez commise.

Au départ, vous avez déclaré

ProgressDialog progressDialog = new ProgressDialog(this); 

et encore vous avez initialisé ici

progressDialog = ProgressDialog.show(context, "", "Sending email", true); 

Alors juste enlever cela de

ProgressDialog progressDialog = new ProgressDialog(this); 

à

ProgressDialog progressDialog; 

Answer 3

Besoin d'initialiser correctement ProgressDialog progressDialog ; Et appelez progressDialog dans votre oncreate().

En fait, votre Locat lancers francs

Causée par: java.lang.NullPointerException à android.content.ContextWrapper.getApplicationInfo (ContextWrapper.java:152) à android.view.ContextThemeWrapper.getTheme (ContextThemeWrapper.java:103) à android.app.AlertDialog.resolveDialogTheme (AlertDialog.java:143) à android.app.AlertDialog (AlertDialog.java:98) à android.app.ProgressDialog (ProgressDialog.java..: 77)

Essayez de cette façon, j'espère que ça va vous aider.

public class MainActivity extends Activity implements View.OnClickListener{ 

EditText fieldEmail, emailSubject, emailBody; 
String strFieldEmail, strEmailSubject, strEmailBody; 
Button buttonLogin; 
Context context = null ; 
Session session = null; 
ProgressDialog progressDialog ; 

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

    progressDialog = new ProgressDialog(MainActivity.this); 
    fieldEmail = (EditText)findViewById(R.id.editEmail); 
    emailSubject = (EditText)findViewById(R.id.editSubject); 
    emailBody = (EditText)findViewById(R.id.editBody); 

    buttonLogin.setOnClickListener(this); 
}