렐름에서 데이터를 가져 오는 중 오류가 발생했습니다.

Question

New! 영역에서 데이터를 검색 할 때 문제가 발생했습니다. 나는 retrofit을 사용하고, Realm (Successful for Sqlite)을 사용하여 데이터를 저장하고 싶지만 데이터베이스에서 데이터를 검색하는 동안 나는 그것을 게시 한 오류가있다.

package np.com.rabindraacharya.retrofitintern.ui; 

import android.content.Intent; 
import android.os.AsyncTask; 
import android.os.Bundle; 
import android.support.design.widget.FloatingActionButton; 
import android.support.design.widget.Snackbar; 
import android.support.v7.app.AppCompatActivity; 
import android.support.v7.widget.LinearLayoutManager; 
import android.support.v7.widget.RecyclerView; 
import android.support.v7.widget.Toolbar; 
import android.util.Log; 
import android.view.Menu; 
import android.view.MenuItem; 
import android.view.View; 

import java.util.List; 

import np.com.rabindraacharya.retrofitintern.Controller.RestManager; 
import np.com.rabindraacharya.retrofitintern.R; 
import np.com.rabindraacharya.retrofitintern.model.Flower; 
import np.com.rabindraacharya.retrofitintern.model.adapter.FlowerAdapter; 
import np.com.rabindraacharya.retrofitintern.model.helper.Constants; 
import np.com.rabindraacharya.retrofitintern.model.helper.FlowerDatabase; 
import np.com.rabindraacharya.retrofitintern.model.helper.Utils; 
import retrofit2.Call; 
import retrofit2.Callback; 
import retrofit2.Response; 

public class MainActivity 
     extends AppCompatActivity 
     implements FlowerAdapter.FlowersClickListener { 
    private RecyclerView recyclerView; 
    private RestManager mManager; 
    FlowerAdapter mFlowerAdapter; 
    FlowerDatabase mDatabase; 

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

     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(); 
      } 
     }); 

     configViews(); 
     mManager = new RestManager(); 
     mDatabase = new FlowerDatabase(); 
     if(Utils.isNetworkAvailable(getApplicationContext())) { 
      getFeed(); 
     } else { 
      getFeedFromDatabase(); 
     } 
    } 

    private void getFeedFromDatabase() { 
     Log.e("RetData", "RetData"); 
     List<Flower> flowerList = mDatabase.getFlower(); 
     for(int i = 0; i < flowerList.size(); i++) { 
      Flower flower = flowerList.get(i); 
      mFlowerAdapter.addFlower(flower); 
     } 
    } 

    private void configViews() { 
     recyclerView = (RecyclerView) findViewById(R.id.recyclerView); 
     recyclerView.setHasFixedSize(true); 
     recyclerView.setRecycledViewPool(new RecyclerView.RecycledViewPool()); 

     LinearLayoutManager verticalLayoutmanager = new LinearLayoutManager(getApplicationContext(), LinearLayoutManager.VERTICAL, false); 
     recyclerView.setLayoutManager(verticalLayoutmanager); 
     mFlowerAdapter = new FlowerAdapter(this); 
     recyclerView.setAdapter(mFlowerAdapter); 
    } 

    @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; 
    } 

    @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); 
    } 

    @Override 
    public void onClick(int position) { 
     Flower selectedFlower = mFlowerAdapter.getSelectedFlower(position); 
     Intent intent = new Intent(MainActivity.this, DetailActivity.class); 
     intent.putExtra(Constants.REFERENCE.FLOWER, selectedFlower); 
     startActivity(intent); 
    } 

    public void getFeed() { 
     Call<List<Flower>> listCall = mManager.getFlowerService().getAllFlowers(); 
     listCall.enqueue(new Callback<List<Flower>>() { 
      @Override 
      public void onResponse(Call<List<Flower>> call, Response<List<Flower>> response) { 
       if(response.isSuccessful()) { 
        List<Flower> flowerList = response.body(); 
        for(int i = 0; i < flowerList.size(); i++) { 
         Flower flower = flowerList.get(i); 

         SaveIntoDatabase task = new SaveIntoDatabase(); 
         task.execute(flower); 
         mFlowerAdapter.addFlower(flower); 
        } 
       } else { 
        int st = response.code(); 
        switch(st) { 
        } 
       } 
      } 

      @Override 
      public void onFailure(Call<List<Flower>> call, Throwable t) { 
      } 
     }); 
    } 

    public class SaveIntoDatabase 
      extends AsyncTask<Flower, Flower, Boolean> { 
     @Override 
     protected void onPreExecute() { 
      super.onPreExecute(); 
     } 

     @Override 
     protected Boolean doInBackground(Flower... params) { 
      Flower flower = params[0]; 
      try { 
       //InputStream stream = new URL("http://services.hanselandpetal.com/photos/" + flower.getPhoto()).openStream(); 
       // Bitmap bitmap = BitmapFactory.decodeStream(stream); 
       //flower.setPicture(bitmap); 
       mDatabase.addFlower(flower); 
       Log.e("ErrorAft", "ErrorAft"); 
      } catch(Exception e) { 

      } 
      return null; 
     } 
    } 
} 

이

을 FlowerDatabase

package np.com.rabindraacharya.retrofitintern.model.helper; 

import android.os.Bundle; 
import android.support.annotation.Nullable; 
import android.support.v7.app.AppCompatActivity; 
import android.util.Log; 

import java.util.ArrayList; 
import java.util.List; 

import io.realm.Realm; 
import io.realm.RealmResults; 
import np.com.rabindraacharya.retrofitintern.model.Flower; 
import np.com.rabindraacharya.retrofitintern.model.adapter.FlowerAdapter; 

/** 
* Created by Rabindra on 8/12/2016. 
*/ 
public class FlowerDatabase 
     extends AppCompatActivity { 
    private Realm myRealm; 
    private int productID; 
    private static FlowerDatabase flowerDatabase; 
    private static List<Flower> arrayListFlower = new ArrayList<>(); 
    private FlowerAdapter flowerAdapter; 

    @Override 
    protected void onCreate(@Nullable Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     myRealm = Realm.getDefaultInstance(); 
     flowerDatabase = this; 
    } 

    public void addFlower(Flower model) { 
     Log.e("RealmData", "RealmData"); 
     myRealm.beginTransaction(); 
     Flower flower = myRealm.createObject(Flower.class); 
     flower.setProductId(model.getProductId()); 
     flower.setCategory(model.getCategory()); 
     flower.setName(model.getName()); 
     flower.setPrice(model.getPrice()); 
     flower.setInstruction(model.getInstruction()); 
     arrayListFlower.add(flower); 
     myRealm.commitTransaction(); 
     flowerAdapter.notifyDataSetChanged(); 
    } 

    public List<Flower> getFlower() { 
     Flower model = new Flower(); 
     productID = model.getProductId(); 

     RealmResults<Flower> results = myRealm.where(Flower.class).findAll(); 
     myRealm.beginTransaction(); 

     for(int i = 0; i < results.size(); i++) { 
      arrayListFlower.add(results.get(i)); 
     } 
     if(results.size() > 0) { 
      productID = myRealm.where(Flower.class).max("id").intValue() + 1; 
     } 
     myRealm.commitTransaction(); 
     flowerAdapter.notifyDataSetChanged(); 
     return arrayListFlower; 
    } 
} 

오류 로그 캣 :

N E/AndroidRuntime : 치명적인 예외 : 주요 프로세스 : np.com.rabindraacharya.retrofitintern, PID : 17091

java.lang.RuntimeException : 활동을 시작할 수 없습니다. 에서 android.app.ActivityThread.performLaunchActivity (ActivityThread.java:2317)에서 java.lang.NullPointerException이 : 1,363,210 ComponentInfo {/ np.com.rabindraacharya.retrofitintern np.com.rabindraacharya.retrofitintern.ui.MainActivity} android.app.ActivityThread.access $ 900 android.app.ActivityThread.handleLaunchActivity (ActivityThread.java:2375) android.app.ActivityThread $ H.handleMessage에서 (ActivityThread.java:164) (ActivityThread.java:1268) android.os.Handler.dispatchMessage (Handler.java:102) android.os.Looper.loop (Looper.java:157) 012 java.lang.reflect.Method.invoke (Method.java:515)에서 java.lang.reflect.Method.invokeNative (기본 방법) 에서 android.app.ActivityThread.main (ActivityThread.java:5377) 에서 3,516, com.android.internal.os.ZygoteInit.main에서 com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run (ZygoteInit.java:1265) (ZygoteInit.java:1081) dalvik.system.NativeStart에서 에서. main (네이티브 메소드) 발생 원인 : java.lang.NullPointerException at np.com.rabindraacharya.retrofitintern.model.helper.FlowerDatabase.getFlower (FlowerDataba se.java:70) np.com.rabindraacharya.retrofitintern.ui.MainActivity.onCreate에서 np.com.rabindraacharya.retrofitintern.ui.MainActivity.getFeedFromDatabase (MainActivity.java:69) (MainActivity.java에서 : 63) android.app.ActivityThread.performLaunchActivity에서 android.app.Activity.performCreate android.app.Instrumentation.callActivityOnCreate (Instrumentation.java:1105에서 (Activity.java:5428) ) (ActivityThread.java에서 : 2281) at android.app.ActivityThread.handleLaunchActivity (ActivityThread.java:2375)android.app.ActivityThread.access $ (900) (ActivityThread.java:164) android.app.ActivityThread $ H.handleMessage (ActivityThread.java:1268) android.os.Handler.dispatchMessage에서 (Handler.java에서에서: 102) android.os.Looper.loop (Looper.java:157) android.app.ActivityThread.main (ActivityThread.java:5377) at java.lang.reflection.Method.invokeNative (네이티브 메소드) at java.lang.reflect.Method.invoke (Method.java:515) at com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run (ZygoteInit.java:1265) 이 줄은 여기 myRealm.where(Flower.class).max("id").intValue() + 1; 더 플라워 경우 NullPointerException이 발생합니다

Answer 1

dalvik.system.NativeStart.main에서 com.android.internal.os.ZygoteInit.main (ZygoteInit.java:1081) 에서 (기본 방법) 개체가 존재합니다. max이 경우 null를 반환 https://realm.io/docs/java/latest/api/io/realm/RealmQuery.html#max-java.lang.String-

당신은 진짜 유효한 이유로 FlowerDatabase 클래스와 AppCompatActivity를 확장하는 시도 할 수 있지만, mDatabase = new FlowerDatabase();으로 flowerDatabase을 인스턴스화하기 때문에 onCreate()가 실행되지 않습니다, 따라서 시스템에 의해 관리되지 않습니다

Answer 2

.

(처음에는 활동이 아니기도합니다. 활동이 있었던 것처럼 Intent으로 작성해야합니다).

기술적으로 개념적으로 잘못 되었기 때문에 기술적으로 코드를 다시 작성해야합니다.

특히 귀하의 FlowerDatabase 클래스는 전적으로 귀하가 영역을 오용하고 있기 때문에 완전히 사용하고 있습니다.