Génération de vues de liste à partir de données récupérées à partir de la base de données

Question

Je rencontre actuellement un problème de génération de vues de liste en fonction des données de ma base de données. J'ai essayé de créer une classe d'entité pour stocker la variable 2 (ID & DESCR) récupérée de la base de données et stockée dans une liste de tableau. Ensuite, j'ai créé une autre liste de chaînes pour stocker la variable (DESCR) que je veux afficher et la mettre dans la liste. PS: J'ai inséré un journal pour tester dans populateList() pour vérifier si j'ai exécuté la méthode populateList() ou non et il n'est pas apparu dans mon chat de journal.

Voici mon code:

package com.example.businesscalculatorassignment; 

import java.io.IOException; 
import java.util.ArrayList; 
import java.util.List; 

import android.os.Bundle; 
import android.widget.*; 
import android.widget.AdapterView.OnItemClickListener; 
import android.app.Activity; 
import android.content.Intent; 
import android.database.Cursor; 
import android.database.SQLException; 
import android.database.sqlite.SQLiteDatabase; 
import android.graphics.Color; 
import android.graphics.Paint; 
import android.graphics.Typeface; 
import android.graphics.drawable.Drawable; 
import android.text.InputType; 
import android.util.Log; 
import android.view.Gravity; 
import android.view.Menu; 
import android.view.View; 
import android.view.View.OnClickListener; 
import android.view.ViewGroup.LayoutParams; 

public class HistoryActivity extends Activity implements OnItemClickListener { 
    private TextView tvHis; 
    private TableRow row1; 
    private SQLiteAdapter mySQLiteAdapter; 
    private ListView lv; 
    DatabaseHelper myDbHelper = new DatabaseHelper(this); 
    private SQLiteDatabase sqLiteDatabase; 
    private ListAdapter HTListAdapter; 
    private ArrayList<HistoryTrans> HTArrayList = new ArrayList<HistoryTrans>(); 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_login); 
     // db testing 

     lv = new ListView(this); 
     try { 
      myDbHelper.createDataBase(); 
     } catch (IOException ioe) { 

      throw new Error("Unable to create database"); 
     } 

     try { 
      myDbHelper.openDataBase(); 
     } catch (SQLException sqle) { 
      throw sqle; 
     } 


     lv.setOnItemClickListener(this); 


     HTListAdapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_2, populateList()); 
     lv.setAdapter(HTListAdapter); 

     LinearLayout ll = new LinearLayout(this); 
     ll.setOrientation(LinearLayout.HORIZONTAL); 
     ll.addView(lv); 
     setContentView(ll); 

    } 

    @SuppressWarnings("deprecation") 
    public List<String> populateList() { 
     mySQLiteAdapter.openToRead(); 
     String test = "testing"; 
     Log.d("test", test); 
     List<String> descList = new ArrayList<String>(); 
     String ID = new String(); 
     String DESCR = new String(); 
     Log.d("ID", ID); 
     Log.d("DESCR", DESCR); 

     String[] columns = new String[] { ID, DESCR }; 
     Cursor cursor = sqLiteDatabase.query(SQLiteAdapter.MYDATABASE_TABLE, 
       columns, null, null, null, null, null); 

     while (cursor.moveToNext()) { 
      ID = cursor.getString(cursor.getColumnIndex(ID)); 
      DESCR = cursor.getString(cursor.getColumnIndex(DESCR)); 

      HistoryTrans HT = new HistoryTrans(); 
      HT.setID(ID); 
      HT.setDESCR(DESCR); 
      HTArrayList.add(HT); 
      descList.add(DESCR); 
      Log.d("ID", ID); 
      Log.d("DESCR", DESCR); 
     } 
     mySQLiteAdapter.close(); 
     return descList; 

    } 

    @Override 
    protected void onResume() { 
     super.onResume(); 
     HTListAdapter = new ArrayAdapter(this, 
       android.R.layout.simple_list_item_1, populateList()); 
     lv.setAdapter(HTListAdapter); 
    } 


@Override 
public void onItemClick(AdapterView<?> arg0, View arg1, int arg2, long arg3) { 

    Toast.makeText(getApplicationContext(), "Clicked on :" + arg2, Toast.LENGTH_SHORT).show(); 

    // We want to redirect to another Activity when the user click an item on the ListView 
    Intent HistoryResultIntent = new Intent(this, HIstoryResult.class); 

    // We have to identify what object, does the user clicked, because we are going to pass only clicked object details to the next activity 
    // What we are going to do is, get the ID of the clicked item and get the values from the ArrayList which has 
    //same array id. 
    HistoryTrans clickedObject = HTArrayList.get(arg2); 

    // We have to bundle the data, which we want to pass to the other activity from this activity 
    String IDbuffer = new String(); 
    IDbuffer = clickedObject.getID(); 

    // Attach the bundled data to the intent 
    HistoryResultIntent.putExtra("ID",IDbuffer); 

    // Start the Activity 
    startActivity(HistoryResultIntent); 

} 
} 

Voici ma classe d'entités juste au cas où nécessaire

package com.example.businesscalculatorassignment; 

import java.io.Serializable; 
import java.util.ArrayList; 

public class HistoryTrans implements Serializable{ 

    private String ID; 
    private String DESCR; 

    private ArrayList<String> IDList = new ArrayList<String>(); 
    private ArrayList<String> DescrList = new ArrayList<String>(); 
    public HistoryTrans(String iD, String dESCR) { 
     super(); 
     ID = iD; 
     DESCR = dESCR; 
    } 
    public HistoryTrans() { 
    } 
    public String getDESCR() { 
     return DESCR; 
    } 
    public void setDESCR(String dESCR) { 
     DESCR = dESCR; 
    } 

    public String getID() { 
     return ID; 
    } 
    public void setID(String iD) { 
     ID = iD; 
    } 


} 

Connexion rapport de chat

04-02 21:56:08.400: E/AndroidRuntime(5125): in writeCrashedAppName, pkgName :com.example.businesscalculatorassignment 
04-02 21:56:08.400: D/AndroidRuntime(5125): file written successfully with content: com.example.businesscalculatorassignment StringBuffer : ;com.example.businesscalculatorassignment 
04-02 21:56:08.400: E/AndroidRuntime(5125): FATAL EXCEPTION: main 
04-02 21:56:08.400: E/AndroidRuntime(5125): Process: com.example.businesscalculatorassignment, PID: 5125 
04-02 21:56:08.400: E/AndroidRuntime(5125): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.businesscalculatorassignment/com.example.businesscalculatorassignment.HistoryActivity}: java.lang.NullPointerException 
04-02 21:56:08.400: E/AndroidRuntime(5125):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195) 
04-02 21:56:08.400: E/AndroidRuntime(5125):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245) 
04-02 21:56:08.400: E/AndroidRuntime(5125):  at android.app.ActivityThread.access$800(ActivityThread.java:135) 
04-02 21:56:08.400: E/AndroidRuntime(5125):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196) 
04-02 21:56:08.400: E/AndroidRuntime(5125):  at android.os.Handler.dispatchMessage(Handler.java:102) 
04-02 21:56:08.400: E/AndroidRuntime(5125):  at android.os.Looper.loop(Looper.java:136) 
04-02 21:56:08.400: E/AndroidRuntime(5125):  at android.app.ActivityThread.main(ActivityThread.java:5021) 
04-02 21:56:08.400: E/AndroidRuntime(5125):  at java.lang.reflect.Method.invokeNative(Native Method) 
04-02 21:56:08.400: E/AndroidRuntime(5125):  at java.lang.reflect.Method.invoke(Method.java:515) 
04-02 21:56:08.400: E/AndroidRuntime(5125):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:827) 
04-02 21:56:08.400: E/AndroidRuntime(5125):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:643) 
04-02 21:56:08.400: E/AndroidRuntime(5125):  at dalvik.system.NativeStart.main(Native Method) 
04-02 21:56:08.400: E/AndroidRuntime(5125): Caused by: java.lang.NullPointerException 
04-02 21:56:08.400: E/AndroidRuntime(5125):  at com.example.businesscalculatorassignment.HistoryActivity.populateList(HistoryActivity.java:71) 
04-02 21:56:08.400: E/AndroidRuntime(5125):  at com.example.businesscalculatorassignment.HistoryActivity.onCreate(HistoryActivity.java:59) 
04-02 21:56:08.400: E/AndroidRuntime(5125):  at android.app.Activity.performCreate(Activity.java:5231) 
04-02 21:56:08.400: E/AndroidRuntime(5125):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1090) 
04-02 21:56:08.400: E/AndroidRuntime(5125):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159) 
04-02 21:56:08.400: E/AndroidRuntime(5125):  ... 11 more 

Merci à l'avance pour aide à condition!

Answer 1

J'ai résolu ma question. Il était en raison d'un curseur incorrect pointant vers des données erronées dans la base de données, donc pas en mesure d'exécuter le code et de générer l'interface.