Question

我按照示例代码但我无法创建我的数据库我不知道为什么，在文件夹中的模拟器中没有任何数据库。这是我的代码这是我的主要活动

public class T5Compras extends Activity {

      private EditText myEditText;
private ListView myListView;
private SimpleCursorAdapter cursorAdapter;
private Cursor cursor;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_t5_compras);


final ComprasDBAdapter comprasDBAdapter = new ComprasDBAdapter(this);


myEditText = (EditText) findViewById(R.id.txtAdd);
myListView = (ListView) findViewById(R.id.lstBuying);

myEditText.setOnKeyListener(new OnKeyListener() {

    @Override
    public boolean onKey(View v, int keyCode, KeyEvent event) {
        // TODO Auto-generated method stub
        if(event.getAction()==KeyEvent.ACTION_DOWN){
            if(keyCode==KeyEvent.KEYCODE_ENTER){

                comprasDBAdapter.open();
                comprasDBAdapter.insertProduct("jorge");
                myEditText.setText("");

                return true;
            }

        }

        return false;

    }
});

/*   ComprasDBAdapter comprasDBAdapter = new ComprasDBAdapter(getApplicationContext());
   comprasDBAdapter.open();
   cursor = comprasDBAdapter.getAllProductItemsCursor();

   cursorAdapter = new  SimpleCursorAdapter(getApplicationContext(), R.layout.lst_layout, cursor, 
           new String[]{ComprasDBAdapter.KEY_PRODUCT,ComprasDBAdapter.KEY_ID}, new int []{R.id.list_txtProduct,R.id.list_txtId });
  */ 
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.t5_compras, menu);
    return true;
}

}

这是我的班级

      public class ComprasDBAdapter {
private static final String DATABASE_NAME = "listCompra.db";
private static final String DATABASE_TABLE = "productItems";
private static final int DATABASE_VERSION = 1;
private SQLiteDatabase db;
public static final String KEY_ID = "_id";
public static final String KEY_PRODUCT = "product";
private ComprasDBOpenHelper dbHelper;



public ComprasDBAdapter(Context _context) {
// TODO Crear una instancia de ComprasDBOpenHelper.
// Inicializar el CursorFactory a null para utilizar el que
// el sistema tiene por defecto.


ComprasDBOpenHelper comprasDBOpenHelper = new ComprasDBOpenHelper(_context, DATABASE_NAME, null, DATABASE_VERSION); 

}

public void close() {
       db.close();

}


public void open() throws SQLiteException {
try
{
      db = dbHelper.getWritableDatabase();
}
catch (SQLiteException ex)
{
      db = dbHelper.getReadableDatabase();
}
}
// Insertar un producto

public long insertProduct(String _product) {
// TODO
    ContentValues cv = new ContentValues();
    cv.put("KEY_PRODUCT", _product);


    db.insert(DATABASE_TABLE, null, cv);

    return 0;
}
// Eliminar un producto según su ID

public boolean removeProduct(int _id) {
//TODO
    db.delete(DATABASE_TABLE, "KEY_ID='_id'", null);
return false;
}

// Actualizar el producto

public boolean updateProduct(long _rowIndex, String _product) {
// TODO
    ContentValues cv = new ContentValues();
    cv.put(KEY_PRODUCT, _product);
    db.update(DATABASE_TABLE, cv, "KEY_PRODUCT='_product'", null);
    return false;
}

public Cursor getAllProductItemsCursor() {
// TODO

return db.rawQuery("SELECT * FROM productItems", null);
}


private class ComprasDBOpenHelper extends SQLiteOpenHelper {

    public ComprasDBOpenHelper(Context context,
    String name,
    CursorFactory factory,
    int version)
    {

    super(context, name, factory, version);


    }
    // Sentencia SQL para crear la nueva base de datos.
    private static final String DATABASE_CREATE = "CREATE TABLE "
    + DATABASE_TABLE + " ("
    + KEY_ID
    + " integer primary key autoincrement, "
    + KEY_PRODUCT
    + " text not null)";
    @Override

    public void onCreate(SQLiteDatabase _db)
    {

    _db.execSQL(DATABASE_CREATE);

    }
    @Override

    public void onUpgrade(SQLiteDatabase _db, int _oldVersion, int _newVersion)
    {
    Log.w("ComprasDBAdapter", "Upgrading from version " +
    _oldVersion + " to " +
    _newVersion + ", which will destroy all old data");
    _db.execSQL("DROP TABLE IF EXISTS " + DATABASE_TABLE);
    onCreate(_db);
    }




}

}

当我尝试插入一些值时，我的应用程序崩溃了，logcat说错误就在那里我认为是数据库因为没有创建数据库

那是logcat

06-16 06:45:08.331: E/AndroidRuntime(1066): FATAL EXCEPTION: main
06-16 06:45:08.331: E/AndroidRuntime(1066): java.lang.NullPointerException
06-16 06:45:08.331: E/AndroidRuntime(1066):     at com.imaginagroup.t5compras.ComprasDBAdapter.open(ComprasDBAdapter.java:43)
06-16 06:45:08.331: E/AndroidRuntime(1066):     at com.imaginagroup.t5compras.T5Compras$1.onKey(T5Compras.java:43)
06-16 06:45:08.331: E/AndroidRuntime(1066):     at android.view.View.dispatchKeyEvent(View.java:7200)
06-16 06:45:08.331: E/AndroidRuntime(1066):     at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1359)
06-16 06:45:08.331: E/AndroidRuntime(1066):     at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1359)
06-16 06:45:08.331: E/AndroidRuntime(1066):     at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1359)
06-16 06:45:08.331: E/AndroidRuntime(1066):     at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1359)
06-16 06:45:08.331: E/AndroidRuntime(1066):     at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchKeyEvent(PhoneWindow.java:1920)
06-16 06:45:08.331: E/AndroidRuntime(1066):     at com.android.internal.policy.impl.PhoneWindow.superDispatchKeyEvent(PhoneWindow.java:1395)
06-16 06:45:08.331: E/AndroidRuntime(1066):     at android.app.Activity.dispatchKeyEvent(Activity.java:2370)
06-16 06:45:08.331: E/AndroidRuntime(1066):     at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchKeyEvent(PhoneWindow.java:1847)
06-16 06:45:08.331: E/AndroidRuntime(1066):     at android.view.ViewRootImpl.deliverKeyEventPostIme(ViewRootImpl.java:3701)
06-16 06:45:08.331: E/AndroidRuntime(1066):     at android.view.ViewRootImpl.handleImeFinishedEvent(ViewRootImpl.java:3651)
06-16 06:45:08.331: E/AndroidRuntime(1066):     at android.view.ViewRootImpl$ViewRootHandler.handleMessage(ViewRootImpl.java:2818)
06-16 06:45:08.331: E/AndroidRuntime(1066):     at android.os.Handler.dispatchMessage(Handler.java:99)
06-16 06:45:08.331: E/AndroidRuntime(1066):     at android.os.Looper.loop(Looper.java:137)
06-16 06:45:08.331: E/AndroidRuntime(1066):     at android.app.ActivityThread.main(ActivityThread.java:5041)
06-16 06:45:08.331: E/AndroidRuntime(1066):     at java.lang.reflect.Method.invokeNative(Native Method)
06-16 06:45:08.331: E/AndroidRuntime(1066):     at java.lang.reflect.Method.invoke(Method.java:511)
06-16 06:45:08.331: E/AndroidRuntime(1066):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
06-16 06:45:08.331: E/AndroidRuntime(1066):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
06-16 06:45:08.331: E/AndroidRuntime(1066):     at dalvik.system.NativeStart.main(Native Method)

Answer 1

从

更改ComprasDBAdapter构造函数

public ComprasDBAdapter(Context _context) {
// TODO Crear una instancia de ComprasDBOpenHelper.
// Inicializar el CursorFactory a null para utilizar el que
// el sistema tiene por defecto.


ComprasDBOpenHelper comprasDBOpenHelper = new ComprasDBOpenHelper(_context, DATABASE_NAME, null, DATABASE_VERSION); 

}

到

public ComprasDBAdapter(Context _context) {
// TODO Crear una instancia de ComprasDBOpenHelper.
// Inicializar el CursorFactory a null para utilizar el que
// el sistema tiene por defecto.


dbHelper  = new ComprasDBOpenHelper(_context, DATABASE_NAME, null, DATABASE_VERSION); 

}

我无法在android中创建数据库

1 个答案: