[英]Table is not found in SQLiteDatabase
我正面临这个奇怪的问题,我搜索了很多,但到目前为止没有用。
我使用以下代码使用从 openhelper 类扩展的 DBHelper 检索 SQLite 数据库。
public class DBHelper extends SQLiteOpenHelper {
public static final int DB_VERSION = 1;
public static final String DB_NAME = "cp.db";
public static final String DB_PATH = "/data/data/abdulla.com.test/databases/";
public static final String ID = "no";
public static final String NAME = "name";
public static final String FORMULA = "formula";
public static final String MW = "mw";
public static final String OMEGA = "omega";
public static final String TC = "tc";
public static final String PC = "pc";
SQLiteDatabase db;
Cursor cursor;
ArrayList<String> elementName;
public DBHelper(Context context) {
super(context, DB_NAME, null, DB_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("drop table if exists elements");
this.onCreate(db);
}
public List<Element> getAllElements() {
List<Element> elementList = new ArrayList<Element>();
// Select All Query
Cursor cursor = null;
String selectQuery = "SELECT * FROM elements";
SQLiteDatabase db = this.getReadableDatabase();
cursor = db.rawQuery(selectQuery, null);
// looping through all rows and adding to list
if (cursor.moveToFirst()) {
do {
Element element = new Element();
element.setNo(Integer.parseInt(cursor.getString(0)));
element.setFormula(cursor.getString(1));
element.setName(cursor.getString(2));
// Adding contact to list
elementList.add(element);
} while (cursor.moveToNext());
}
// return contact list
return elementList;
}
}
这是从 MainActivity 类中捕获的
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
DBHelper helper = new DBHelper(this);
List<Element> elementList = helper.getAllElements();
for(Element element : elementList){
String log = "no: "+element.getNo();
Log.d("No: ", log);
}
}
}
我收到此错误:
java.lang.RuntimeException: Unable to start activity
ComponentInfo{abdulla.com.test/abdulla.com.test.MainActivity}:
android.database.sqlite.SQLiteException: no such table: elements (code 1):
, while compiling: SELECT * FROM elements
我知道元素表在那里
有什么帮助吗?
问题可能出在您的onUpgrade()
方法中。 如果您的数据库没有版本,应用程序会尝试升级它,并删除您的表( db.execSQL("drop table if exists elements");
)。
解决方案: 将版本设置为 DB或更改onUpgrade()
方法(删除 DROP 语句)。
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