AWS DynamoDB RuntimeException

Question

Hey Leute ich versuche, einige Daten aus einer Tabelle in DynamoDB in Android Studio zu lesen und trotz meiner mühsamen Bemühungen, bekomme ich diese Ausnahme. Irgendwelche Ideen, wie man es repariert?

04-06 19:25:11.688 23407-23423/com.example.ali.dynamodb E/AndroidRuntime: FATAL EXCEPTION: AsyncTask #1 
Process: com.example.ali.dynamodb, PID: 23407 
java.lang.RuntimeException: An error occurred while executing doInBackground() 
at android.os.AsyncTask$3.done(AsyncTask.java:309) 
at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:354) 
at java.util.concurrent.FutureTask.setException(FutureTask.java:223) 
at java.util.concurrent.FutureTask.run(FutureTask.java:242) 
at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:234) 
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1113) 
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:588) 
at java.lang.Thread.run(Thread.java:818) 
Caused by: java.lang.NullPointerException: Attempt to invoke interface method 'com.amazonaws.auth.AWSCredentials com.amazonaws.auth.AWSCredentialsProvider.getCredentials()' on a null object reference 
at com.amazonaws.services.dynamodbv2.AmazonDynamoDBClient.invoke(AmazonDynamoDBClient.java:3504) 
at com.amazonaws.services.dynamodbv2.AmazonDynamoDBClient.getItem(AmazonDynamoDBClient.java:929) 
at com.amazonaws.mobileconnectors.dynamodbv2.dynamodbmapper.DynamoDBMapper.load(DynamoDBMapper.java:393) 
at com.amazonaws.mobileconnectors.dynamodbv2.dynamodbmapper.DynamoDBMapper.load(DynamoDBMapper.java:466) 
at com.amazonaws.mobileconnectors.dynamodbv2.dynamodbmapper.DynamoDBMapper.load(DynamoDBMapper.java:340) 
at com.example.ali.dynamodb.MainActivity$BackT.doInBackground(MainActivity.java:172) 
at com.example.ali.dynamodb.MainActivity$BackT.doInBackground(MainActivity.java:161) 
at android.os.AsyncTask$2.call(AsyncTask.java:295) 
at java.util.concurrent.FutureTask.run(FutureTask.java:237) 
at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:234)  
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1113)  
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:588)  
at java.lang.Thread.run(Thread.java:818) 

MainActivity.java:

public class MainActivity extends AppCompatActivity { 
     private CognitoCachingCredentialsProvider credentialsProvider; 


     @Override 
     protected void onCreate(Bundle savedInstanceState) { 
       super.onCreate(savedInstanceState); 
       setContentView(R.layout.activity_main); 
       Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar); 
       setSupportActionBar(toolbar); 

       String forumName = "Amazon DynamoDB"; 
       String threadSubject = "DynamoDB Thread 1"; 

       FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab); 
       fab.setOnClickListener(new View.OnClickListener() { 
         @Override 
         public void onClick(View view) { 
           Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG) 
               .setAction("Action", null).show(); 
         } 
       }); 

       // Initialize the Amazon Cognito credentials provider 
       CognitoCachingCredentialsProvider credentialsProvider = new CognitoCachingCredentialsProvider(
           getApplicationContext(), 
           "eu-west-1:c9e997aa-5f3e-4c0a-b3d9-f6faf2a39ab7", // Identity Pool ID 
           Regions.EU_WEST_1 // Region 
       ); 


       new BackT().execute(""); 
     } 

     @Override 
     public boolean onCreateOptionsMenu(Menu menu) { 
       // Inflate the menu; this adds items to the action bar if it is present. 
       getMenuInflater().inflate(R.menu.menu_main, menu); 
       return true; 
     } 

     private static void GetUserName(DynamoDBMapper mapper, int id) throws Exception { 
       UserTable userTable = mapper.load(UserTable.class, id); 
     } 


     @Override 
     public boolean onOptionsItemSelected(MenuItem item) { 
       // Handle action bar item clicks here. The action bar will 
       // automatically handle clicks on the Home/Up button, so long 
       // as you specify a parent activity in AndroidManifest.xml. 
       int id = item.getItemId(); 

       //noinspection SimplifiableIfStatement 
       if (id == R.id.action_settings) { 
         return true; 
       } 

       return super.onOptionsItemSelected(item); 
     } 


     private class BackT extends AsyncTask<String, Void, String> { 
       @Override 
       protected String doInBackground(String... params) { 
         AmazonDynamoDBClient ddbClient = new AmazonDynamoDBClient(credentialsProvider); 

         TextView sample1 = (TextView) findViewById(R.id.sample1); 
         TextView sample2 = (TextView) findViewById(R.id.sample2); 
         TextView sample3 = (TextView) findViewById(R.id.sample3); 

         // Getting items from the row specified with primary key 
         DynamoDBMapper mapper = new DynamoDBMapper(ddbClient); 
         UserTable userTable = mapper.load(UserTable.class, 1); 
         String result1 = userTable.getFirstName(); 
         String result2 = userTable.getSurname(); 
         String result3 = userTable.getUserName(); 

         sample1.setText(result1); 
         sample2.setText(result2); 
         sample3.setText(result3); 

         mapper.save(userTable); 
         return "Executed"; 
       } 

       @Override 
       protected void onPostExecute(String result) { 
       } 

       @Override 
       protected void onPreExecute() { 
       } 

       @Override 
       protected void onProgressUpdate(Void... values) { 
       } 
     } 
} 

UserTable.java:

@DynamoDBTable(tableName = "USER_TABLE") 
public class UserTable { 
     private String dateOfBirth; 
     private String emailAddress; 
     private String FirstN; 
     private String SurN; 
     private String User_Acc_ID; 
     private String User_Address_ID; 
     private int User_ID; 
     private String User_Name; 

     @DynamoDBAttribute(attributeName = "DATE_OF_BIRTH") 
     public String getDOB() { 
       return dateOfBirth; 
     } 

     @DynamoDBAttribute(attributeName = "EMAIL_ADDRESS") 
     public String getEmailAddress() { 
       return emailAddress; 
     } 

     @DynamoDBAttribute(attributeName = "FIRST_NAME") 
     public String getFirstName() { 
       return FirstN; 
     } 

     @DynamoDBAttribute(attributeName = "SURNAME") 
     public String getSurname() { 
       return SurN; 
     } 

     @DynamoDBAttribute(attributeName = "USER_ACC_ID") 
     public String getUser_Acc_ID() { 
       return User_Acc_ID; 
     } 

     @DynamoDBAttribute(attributeName = "USER_ADDRESS_ID") 
     public String getUser_Address_ID() { 
       return User_Address_ID; 
     } 

     @DynamoDBHashKey(attributeName = "USER_ID") 
     public int getUserID() { 
       return User_ID; 
     } 

     public void setUserID(int user_id){ 
       this.User_ID = User_ID; 
     } 


     @DynamoDBAttribute(attributeName = "USER_ID") 
     public String getUserName() { 
       return User_Name; 
     } 

} 

Answer 1

erstellen Sie eine zweite Instanz credentialsProvider, die das Klassenmitglied versteckt. Als Ergebnis wird das verwendete Klassenelement credentialsProvider nicht initialisiert und null.

Entfernen Sie CognitoCachingCredentialsProvider in der Initialisierungszeile.

Edit: Ich bin nicht mit Android-Specials vertraut. Aber von einem jav perspecptive es sollte Schleife wie:

new BackT(credentialsProvider).execute(""); 

Und die backt Klasse sollte einen Konstruktor enthalten:

private AWSCredentialsProvider localCredProvider = null; 
public BackT(AWSCredentialsProvider credProvider) 
{ 
    if (null != credProvider) 
    { 
    this.localCredProvider = credProvider; 
    } 
    else 
    { 
     // add some error logging here 
    } 
} 

und die DB-Initialisierung sollte das lokale Element verwenden:

new AmazonDynamoDBClient(localCredProvider); 

Etwas auf diese Weise solltest du versuchen. Andernfalls gibt der Anmeldeinformationsanbieter irgendwo einen NULL-Wert zurück.