Loading existing database in android

Question

Possible Duplicate:
How to use an existing database with an Android application

I'm doing a project in Android, and i'm trying to load the existing database to my app. And i'm getting an error.

public class DBHelper extends SQLiteOpenHelper{

private static String DB_PATH = "/data/data/com.example.qbox/databases/";
private static String DB_NAME = "frases.db";

private SQLiteDatabase myDatabase;
private final Context _context;

public static final String KEY_ID = "_id";
public final static String KEY_FRASE = "frase";
public final static String KEY_AUTOR = "autor";
public final static String KEY_CATEGORIA = "categoria";
public final static String KEY_FAVORITA = "favorita";

public static final String DATABASE_TABLE = "frases";

private static final String[] cols = new String[] { KEY_ID, KEY_FRASE, KEY_AUTOR, KEY_CATEGORIA, KEY_FAVORITA};


public DBHelper(Context context) {

        super(context, DB_NAME, null, 1);
        this._context = context;
    }        


/**
* create new db and then rewrite records.
* */
public void createDataBase() throws IOException{

    boolean dbExist = checkDataBase();

    if(dbExist){
        // dn exists ... nothing to do
    } else {
      this.getReadableDatabase();
    try {

    copyDataBase();

    } catch (IOException e) {
    throw new Error("Error copiando Base de Datos");
    }
}

}

/**
* Check if db exists
*/
private boolean checkDataBase(){

SQLiteDatabase checkDB = null;

try{

String myPath = DB_PATH + DB_NAME;
checkDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);

} catch(SQLiteException e) {

}
if(checkDB != null){

    checkDB.close();

}
return checkDB != null ? true : false;
}

/**
*  Copy Database
 **/
private void copyDataBase() throws IOException{

    InputStream myInput = _context.getAssets().open(DB_NAME);
    String outFileName = DB_PATH + DB_NAME;
    OutputStream myOutput = new FileOutputStream(outFileName);

    byte[] buffer = new byte[1024];
    int length;
    while (( length = myInput.read(buffer)) > 0){
        myOutput.write(buffer, 0, length);
    }

    myOutput.flush();
    myOutput.close();
    myInput.close();

}

public void open() throws SQLException{
    try {
        createDataBase();
    } catch (IOException e) {
        throw new Error("Ha sido imposible crear la Base de Datos");
    }

    String myPath = DB_PATH + DB_NAME;
    myDatabase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
}

@Override
public synchronized void close() {
    if(myDatabase != null)
        myDatabase.close();
    super.close();
}

@Override
public void onCreate(SQLiteDatabase db) {

}

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

}

/**
* INSERTAR NUEVA FRASE
* */
public long insertarFrase(Integer id,String frase, String autor, String categoria, String favorita ) {
    ContentValues newValues = new ContentValues();
    newValues.put(KEY_ID, id);
    newValues.put(KEY_FRASE,frase);
    newValues.put(KEY_AUTOR, autor);
    newValues.put(KEY_CATEGORIA, categoria);
    newValues.put(KEY_FAVORITA, favorita);
    return myDatabase.insert(DATABASE_TABLE, null, newValues);
}

/**
* BORRAR FRASE CON _id = _rowIndex
* */
public boolean removerFrase(long _rowIndex) {
    return myDatabase.delete(DATABASE_TABLE, KEY_ID + "=" + _rowIndex, null) > 0;
}

/**
* ACTUALIZAR FRASE _id = _rowIndex
* */
public boolean updateFrase(Integer _rowIndex, String frase, String autor, String categoria, String favorita ) {
    ContentValues newValues = new ContentValues();
    newValues.put(KEY_FRASE,frase);
    newValues.put(KEY_AUTOR, autor);
    newValues.put(KEY_CATEGORIA, categoria);
    newValues.put(KEY_FAVORITA, favorita);
    return myDatabase.update(DATABASE_TABLE, newValues, KEY_ID + "=" + _rowIndex, null) > 0;
}


  public List<Frase> getTodasLasFrases() {
        List<Frase> contacts = new ArrayList<Frase>();

        Cursor cursor = myDatabase.query(DBHelper.DATABASE_TABLE,
            cols, null, null, null, null, null);

        cursor.moveToFirst();
        while (!cursor.isAfterLast()) {
          Frase frase = cursorFrase(cursor);
          contacts.add(frase);
          cursor.moveToNext();
        }
        cursor.close();
        return contacts;
      }
  private Frase cursorFrase(Cursor cursor) {
      Frase frase = new Frase();
          frase.setId(cursor.getLong(0));
          frase.setFrase(cursor.getString(1));
          frase.setAutor(cursor.getString(2));
          frase.setCat(cursor.getString(3));
          frase.setFav(cursor.getString(4));
      return frase;
  }
  public Frase getContact(int id) {

        Cursor cursor = myDatabase.query(DBHelper.DATABASE_TABLE, cols, this.KEY_ID + "=?",
                new String[] { String.valueOf(id) }, null, null, null, null);
        if (cursor != null)
            cursor.moveToFirst();

        Frase frase = cursorFrase(cursor);

        return frase;
  }

}

in the main class

public class Home extends Activity implements OnClickListener {

ImageButton favBtn,catBtn,infoBtn,shareBtn;

DBHelper db;    

ListView lv;
List<Frase> values;
ArrayAdapter<Frase> adapter;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    setContentView(R.layout.home);


    favBtn =(ImageButton) findViewById(R.id.favBtn);
    catBtn = (ImageButton) findViewById(R.id.catBtn);
    infoBtn = (ImageButton) findViewById(R.id.infoBtn);
    shareBtn = (ImageButton) findViewById(R.id.shareBtn);

    infoBtn.setOnClickListener(this);
    catBtn.setOnClickListener(this);
    favBtn.setOnClickListener(this);
    shareBtn.setOnClickListener(this);
    prepararFrases();     
}

@Override
public void onClick(View v) {

}

public void prepararFrases(){

    db.open();
      /*
    values = db.getTodasLasFrases();
    adapter = new ArrayAdapter<Frase>(this,
            android.R.layout.simple_list_item_1, values);

    //setListAdapter(adapter);


    for (Frase cn : values) {
        String log = "Id: "+cn.getId()+" ,Frase: " + cn.getFrase()+ " ,Autor: " + cn.getAutor();
        Log.d("Name: ", log);
    }  

    db.close();*/

}

}

The error:

11-10 21:45:08.366: E/AndroidRuntime(5535): Uncaught handler: thread main exiting due to uncaught exception
11-10 21:45:08.376: E/AndroidRuntime(5535): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.qbox/com.example.quotebox.Home}: java.lang.NullPointerException
11-10 21:45:08.376: E/AndroidRuntime(5535):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2503)
11-10 21:45:08.376: E/AndroidRuntime(5535):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2519)
11-10 21:45:08.376: E/AndroidRuntime(5535):     at android.app.ActivityThread.access$2200(ActivityThread.java:123)
11-10 21:45:08.376: E/AndroidRuntime(5535):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1870)
11-10 21:45:08.376: E/AndroidRuntime(5535):     at android.os.Handler.dispatchMessage(Handler.java:99)
11-10 21:45:08.376: E/AndroidRuntime(5535):     at android.os.Looper.loop(Looper.java:123)
11-10 21:45:08.376: E/AndroidRuntime(5535):     at android.app.ActivityThread.main(ActivityThread.java:4370)
11-10 21:45:08.376: E/AndroidRuntime(5535):     at java.lang.reflect.Method.invokeNative(Native Method)
11-10 21:45:08.376: E/AndroidRuntime(5535):     at java.lang.reflect.Method.invoke(Method.java:521)
11-10 21:45:08.376: E/AndroidRuntime(5535):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
11-10 21:45:08.376: E/AndroidRuntime(5535):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
11-10 21:45:08.376: E/AndroidRuntime(5535):     at dalvik.system.NativeStart.main(Native Method)
11-10 21:45:08.376: E/AndroidRuntime(5535): Caused by: java.lang.NullPointerException
11-10 21:45:08.376: E/AndroidRuntime(5535):     at com.example.qbox.Home.prepararFrases(Home.java:74)
11-10 21:45:08.376: E/AndroidRuntime(5535):     at com.example.qbox.Home.onCreate(Home.java:45)
11-10 21:45:08.376: E/AndroidRuntime(5535):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
11-10 21:45:08.376: E/AndroidRuntime(5535):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2466)
11-10 21:45:08.376: E/AndroidRuntime(5535):     ... 11 more

http://stackoverflow.com/questions/9109438/how-to-use-an-existing-database-with-an-android-application/9109728#9109728 — Yaqub Ahmad, Nov 11 '12 at 04:27

score 2 · Answer 1 · answered Nov 11 '12 at 00:52

You have a nullPointerException when you try to open db. You have declared it but you didn't create an instance of it. In the main activity in onCreate() method create a new instance of you DBHelper class and then pass a context to its constructor as an argument:

db = new DBHelper(getBaseContext());

score 1 · Answer 2 · answered Nov 11 '12 at 00:57

Please format logcat traces in your posts. It's very hard to read otherwise.

Please also learn how to understand exception stack traces and how to debug your app. It will save *everyone", including you, time.

The logcat shows that the null pointer exception is in prepareFrases(), specifically line 74.

Caused by: java.lang.NullPointerException 11-10 21:45:08.376: E/AndroidRuntime(5535): at com.example.qbox.Home.prepararFrases(Home.java:74)

You don't tell us what line 74 is but since it contains only one executable statement, it must be this:

db.open();

The reason it is null (which if you have stepped through in your debugger you would know) is that you have not initialised it, something like:

db = new DBHelper(this);

Sorry, i'm very new to this page, and to android... i feel a little bit stupid! thank's very much for your answers. — Fede, Nov 11 '12 at 04:43

Loading existing database in android

2 Answers2