erreur avec le programme de base de données android

06-29 01:24:15.882: ERROR/AndroidRuntime(747): Uncaught handler: thread main exiting due to uncaught exception 
06-29 01:24:15.922: ERROR/AndroidRuntime(747): java.lang.RuntimeException: Unable to start activity ComponentInfo{one.two/one.two.Arrival}: java.lang.NullPointerException 
06-29 01:24:15.922: ERROR/AndroidRuntime(747):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2268) 
06-29 01:24:15.922: ERROR/AndroidRuntime(747):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2284) 
06-29 01:24:15.922: ERROR/AndroidRuntime(747):  at android.app.ActivityThread.access$1800(ActivityThread.java:112) 
06-29 01:24:15.922: ERROR/AndroidRuntime(747):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1692) 
06-29 01:24:15.922: ERROR/AndroidRuntime(747):  at android.os.Handler.dispatchMessage(Handler.java:99) 
06-29 01:24:15.922: ERROR/AndroidRuntime(747):  at android.os.Looper.loop(Looper.java:123) 
06-29 01:24:15.922: ERROR/AndroidRuntime(747):  at android.app.ActivityThread.main(ActivityThread.java:3948) 
06-29 01:24:15.922: ERROR/AndroidRuntime(747):  at java.lang.reflect.Method.invokeNative(Native Method) 
06-29 01:24:15.922: ERROR/AndroidRuntime(747):  at java.lang.reflect.Method.invoke(Method.java:521) 
06-29 01:24:15.922: ERROR/AndroidRuntime(747):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:782) 
06-29 01:24:15.922: ERROR/AndroidRuntime(747):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:540) 
06-29 01:24:15.922: ERROR/AndroidRuntime(747):  at dalvik.system.NativeStart.main(Native Method) 
06-29 01:24:15.922: ERROR/AndroidRuntime(747): Caused by: java.lang.NullPointerException 
06-29 01:24:15.922: ERROR/AndroidRuntime(747):  at one.two.DBAdapter.getAllTitles(DBAdapter.java:167) 
06-29 01:24:15.922: ERROR/AndroidRuntime(747):  at one.two.Arrival.getData(Arrival.java:35) 
06-29 01:24:15.922: ERROR/AndroidRuntime(747):  at one.two.Arrival.onCreate(Arrival.java:21) 
06-29 01:24:15.922: ERROR/AndroidRuntime(747):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1123) 
06-29 01:24:15.922: ERROR/AndroidRuntime(747):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2231) 
06-29 01:24:15.922: ERROR/AndroidRuntime(747):  ... 11 more

ma classe pour appeler la base de donnéeserreur avec le programme de base de données android

package one.two; 

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

import android.app.ListActivity; 
import android.os.Bundle; 
import android.widget.ArrayAdapter; 
import android.widget.ListView; 

public class Arrival extends ListActivity 
{ 
    private ListView listView; 
    DBAdapter db = new DBAdapter(this); 

    /** Called when the activity is first created. */ 
    public void onCreate(Bundle savedInstanceState) 
    { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.main); 
     getData(); 
     // db.open(); 
     listView = (ListView) findViewById(android.R.id.list); 
     // db.close(); 
    } 

    private void getData() 
    { 
     // show some display that you are going to open db 
     db.open(); 
     // show some display that you have opened 

     // redundant see below statement ---- List<String> items = new ArrayList<String>(); 
     // call the DBAdapter method to getAllTitles() 
     List<String> items = DBAdapter.getAllTitles(); 
     // iterate through the items one by one thru display statement or show 
     // on layout 
     // check how to do that 

     ArrayAdapter<String> titles = new ArrayAdapter<String>(this, 
       R.layout.main, items); 

     db.close(); 
    } 

}

Mon DBAdapter.java

package one.two; 

import java.io.FileOutputStream; 
import java.io.IOException; 
import java.io.InputStream; 
import java.io.OutputStream; 
import java.util.List; 

import android.app.ListActivity; 
import android.content.Context; 
import android.database.Cursor; 
import android.database.SQLException; 
import android.database.sqlite.SQLiteDatabase; 
import android.database.sqlite.SQLiteException; 
import android.database.sqlite.SQLiteOpenHelper; 
import android.util.Log; 
import java.util.ArrayList; 

public class DBAdapter extends ListActivity 
{ 
    private static String DB_PATH = "/data/data/one.two/databases/"; 
    private static final String DATABASE_NAME = "ferry.db"; 
    private static final String DATABASE_TABLE = "port"; 
    public static Context context; 

    public String status = "status"; 
    public String id = "id"; 
    public String arrival = "arrival"; 
    public String destination = "destination"; 
    public String ferry = "ferry"; 

    //null constructor 
    public DBAdapter() 
    { 

    } 

    //overloaded non-null constructor 
    public DBAdapter(Context context) 
    { 

    } 

    public class DatabaseHelper extends SQLiteOpenHelper 
    { 
     Context context; 
     DatabaseHelper(Context context) 
     { 
      super(context, DATABASE_NAME, null, DATABASE_VERSION); 
      this.context = context; 

     }//end constructor DatabaseHelper 

     @Override 
     public void onUpgrade(SQLiteDatabase db, int oldVersion, 
       int newVersion) 
     { 
     }//end onUpgrade() 

     @Override 
     public void onCreate(SQLiteDatabase db) 
     { 
      boolean dbExist = checkDatabase(); 

      if (dbExist) 
      { 
      } 
      else 
      { 
       this.getReadableDatabase(); 
       try 
       { 
        copyDataBase(); 
       } 
       catch (IOException e) 
       { 
        throw new Error("Error copying database"); 
       } 
      } 
     }//end onCreate() 
    }// end class DatabaseHelper 

    private static DatabaseHelper DBHelper; 
    private static SQLiteDatabase db; 

    private static final int DATABASE_VERSION = 1; 

    //// context brought up ///////////// 
    //private final Context context; 


     private boolean checkDatabase() 
     { 
      SQLiteDatabase checkDB = null; 
      try 
      { 
       String myPath = DB_PATH + DATABASE_NAME; 
       checkDB = SQLiteDatabase.openDatabase(myPath, null, 
         SQLiteDatabase.OPEN_READONLY); 
      } 
      catch (SQLiteException e) 
      { 

       // database doesn't exist yet 
      } 
      if (checkDB != null) 
      { 

       checkDB.close(); 
      } 
      return checkDB != null ? true : false; 
     }//end checkDatabase() 

     private void copyDataBase() throws IOException 
     { 

      // Open your local db as the input stream 
      InputStream myInput = context.getAssets().open(DATABASE_NAME); 

      // Path to the just created empty db 
      String outFileName = DB_PATH + DATABASE_NAME; 

      // Open the empty db as the output stream 
      OutputStream myOutput = new FileOutputStream(outFileName); 

      // transfer bytes from the inputfile to the outputfile 
      byte[] buffer = new byte[1024]; 
      int length; 
      while ((length = myInput.read(buffer)) > 0) 
      { 
       myOutput.write(buffer, 0, length); 
      } 

      // Close the streams 
      myOutput.flush(); 
      myOutput.close(); 
      myInput.close(); 

     }//end copyDataBase() 

     public void DBAdapter() throws SQLException 
     { 
      String myPath = DB_PATH + DATABASE_NAME; 
      db = SQLiteDatabase.openDatabase(myPath, null, 
        SQLiteDatabase.OPEN_READONLY); 
     }//end DBAdapter() 
     public void open() 
     { 
      //Open the database 
      String myPath = DB_PATH + DATABASE_NAME; 
      db = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY); 

     } 
     // ---closes the database--- 
     public void close() 
     { 
      DBHelper.close(); 
     }//end close() 

     public static List<String> getAllTitles() 
     { 

      List<String> titles = new ArrayList<String>(); 

       Cursor c=null; 
       c = db.query("port", 
         new String[] { "status", "id", "arrival", 
           "destination", "ferry" }, null, null, 
         null, null, null); 
       try { 
        if (c!=null) { 
         for (c.moveToFirst(); !c.isAfterLast(); c.moveToNext()) 
         { 
          DBAdapter title = new DBAdapter(context); 
          title.status = c.getString(0); 
          title.id = c.getString(1); 
          title.arrival = c.getString(2); 
          title.destination = c.getString(3); 
          title.ferry = c.getString(4); 
         } 
        } 
       } finally { 
        if (c!=null) { 
        c.close(); 
       } 

     } 
      return titles; 
     }//end getAllTitles() 
    }//end class DBAdapter

Source

2010-06-29 User358218

Vous appelez jamais open() sur votre objet. Vous utilisez un appel statique dans votre code, mais cet appel statique dépend des méthodes non statiques appelées pour configurer les membres de données statiques. Ainsi, lorsque vous appelez db.query()db est null, d'où l'exception de pointeur NULL. Votre architecture globale est fondamentalement défectueuse. Vous devez instancier votre objet DBAdapter et appeler plusieurs méthodes telles que open à partir de votre méthode statique. Cependant, dans votre méthode statique, vous comptez sur l'objet context en cours de définition. Cependant, vous ne définissez pas cela avant d'appeler le constructeur. Vous devez vous assurer que vos références sont définies avant d'essayer de les utiliser. Je suggère de ne pas essayer de faire un appel statique comme ceci, sauf si vous voulez lui passer un objet Context. De là, vous devrez instancier l'objet DBAdapter et appeler les méthodes d'installation appropriées (comme open) avant de pouvoir interagir avec la base de données.

Modifier

Basé sur relisant votre code, changez votre classe d'adaptateur de base de données pour supprimer la méthode statique:

package one.two; 

import java.io.FileOutputStream; 
import java.io.IOException; 
import java.io.InputStream; 
import java.io.OutputStream; 
import java.util.List; 

import android.app.ListActivity; 
import android.content.Context; 
import android.database.Cursor; 
import android.database.SQLException; 
import android.database.sqlite.SQLiteDatabase; 
import android.database.sqlite.SQLiteException; 
import android.database.sqlite.SQLiteOpenHelper; 
import android.util.Log; 
import java.util.ArrayList; 

public class DBAdapter extends ListActivity 
{ 
    private static String DB_PATH = "/data/data/one.two/databases/"; 
    private static final String DATABASE_NAME = "ferry.db"; 
    private static final String DATABASE_TABLE = "port"; 
    public static Context context; 

    public String status = "status"; 
    public String id = "id"; 
    public String arrival = "arrival"; 
    public String destination = "destination"; 
    public String ferry = "ferry"; 

    //null constructor 
    public DBAdapter() 
    { 

    } 

    //overloaded non-null constructor 
    public DBAdapter(Context context) 
    { 

    } 

    public class DatabaseHelper extends SQLiteOpenHelper 
    { 
     Context context; 
     DatabaseHelper(Context context) 
     { 
      super(context, DATABASE_NAME, null, DATABASE_VERSION); 
      this.context = context; 

     }//end constructor DatabaseHelper 

     @Override 
     public void onUpgrade(SQLiteDatabase db, int oldVersion, 
       int newVersion) 
     { 
     }//end onUpgrade() 

     @Override 
     public void onCreate(SQLiteDatabase db) 
     { 
      boolean dbExist = checkDatabase(); 

      if (dbExist) 
      { 
      } 
      else 
      { 
       this.getReadableDatabase(); 
       try 
       { 
        copyDataBase(); 
       } 
       catch (IOException e) 
       { 
        throw new Error("Error copying database"); 
       } 
      } 
     }//end onCreate() 
    }// end class DatabaseHelper 

    private static DatabaseHelper DBHelper; 
    private static SQLiteDatabase db; 

    private static final int DATABASE_VERSION = 1; 

    //// context brought up ///////////// 
    //private final Context context; 


     private boolean checkDatabase() 
     { 
      SQLiteDatabase checkDB = null; 
      try 
      { 
       String myPath = DB_PATH + DATABASE_NAME; 
       checkDB = SQLiteDatabase.openDatabase(myPath, null, 
         SQLiteDatabase.OPEN_READONLY); 
      } 
      catch (SQLiteException e) 
      { 

       // database doesn't exist yet 
      } 
      if (checkDB != null) 
      { 

       checkDB.close(); 
      } 
      return checkDB != null ? true : false; 
     }//end checkDatabase() 

     private void copyDataBase() throws IOException 
     { 

      // Open your local db as the input stream 
      InputStream myInput = context.getAssets().open(DATABASE_NAME); 

      // Path to the just created empty db 
      String outFileName = DB_PATH + DATABASE_NAME; 

      // Open the empty db as the output stream 
      OutputStream myOutput = new FileOutputStream(outFileName); 

      // transfer bytes from the inputfile to the outputfile 
      byte[] buffer = new byte[1024]; 
      int length; 
      while ((length = myInput.read(buffer)) > 0) 
      { 
       myOutput.write(buffer, 0, length); 
      } 

      // Close the streams 
      myOutput.flush(); 
      myOutput.close(); 
      myInput.close(); 

     }//end copyDataBase() 

     public void DBAdapter() throws SQLException 
     { 
      String myPath = DB_PATH + DATABASE_NAME; 
      db = SQLiteDatabase.openDatabase(myPath, null, 
        SQLiteDatabase.OPEN_READONLY); 
     }//end DBAdapter() 
     public void open() 
     { 
      //Open the database 
      String myPath = DB_PATH + DATABASE_NAME; 
      db = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY); 

     } 
     // ---closes the database--- 
     public void close() 
     { 
      DBHelper.close(); 
     }//end close() 

     public List<String> getAllTitles() 
     { 

      List<String> titles = new ArrayList<String>(); 

       Cursor c=null; 
       c = db.query("port", 
         new String[] { "status", "id", "arrival", 
           "destination", "ferry" }, null, null, 
         null, null, null); 
       try { 
        if (c!=null) { 
         for (c.moveToFirst(); !c.isAfterLast(); c.moveToNext()) 
         { 
          DBAdapter title = new DBAdapter(context); 
          title.status = c.getString(0); 
          title.id = c.getString(1); 
          title.arrival = c.getString(2); 
          title.destination = c.getString(3); 
          title.ferry = c.getString(4); 
         } 
        } 
       } finally { 
        if (c!=null) { 
        c.close(); 
       } 

     } 
      return titles; 
     }//end getAllTitles() 
    }//end class DBAdapter

Et changer votre classe d'arrivée pour utiliser la méthode non statique:

package one.two; 

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

import android.app.ListActivity; 
import android.os.Bundle; 
import android.widget.ArrayAdapter; 
import android.widget.ListView; 

public class Arrival extends ListActivity 
{ 
    private ListView listView; 
    DBAdapter db = new DBAdapter(this); 

    /** Called when the activity is first created. */ 
    public void onCreate(Bundle savedInstanceState) 
    { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.main); 
     getData(); 
     // db.open(); 
     listView = (ListView) findViewById(android.R.id.list); 
     // db.close(); 
    } 

    private void getData() 
    { 
     // show some display that you are going to open db 
     db.open(); 
     // show some display that you have opened 

     // redundant see below statement ---- List<String> items = new ArrayList<String>(); 
     // call the DBAdapter method to getAllTitles() 
     List<String> items = db.getAllTitles(); 
     // iterate through the items one by one thru display statement or show 
     // on layout 
     // check how to do that 

     ArrayAdapter<String> titles = new ArrayAdapter<String>(this, 
       R.layout.main, items); 

     db.close(); 
    } 

}

Source

2010-06-29 02:20:06

Cette instruction n'ouvre-t-elle pas la base de données? \t Chaîne myPath = DB_PATH + DATABASE_NAME; \t \t \t db = SQLiteDatabase.openDatabase (myPath, null, \t \t \t \t \t SQLiteDatabase.OPEN_READONLY); – User358218

Oui, mais vous l'appelez après avoir utilisé la base de données ... vous devez placer l'appel pour instancier l'objet DBAdapter avant d'essayer d'utiliser l'objet db. En outre, vous devez toujours passer cette méthode un objet contextuel. –

Désolé, je ne comprends pas vraiment ce que vous voulez dire en utilisant la base de données. – User358218

erreur avec le programme de base de données android

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