Question

我创建了一个名为_id的列名，但是当我使用getAllRows()方法运行并在ListView中查看数据库时，它显示错误(no such column: _id (code 1): , while compiling: SELECT DISTINCT _id, eventTitle, date, destination, durationTime, alarmTime FROM Event.)。以下是我的代码和我的错误消息请帮助我并教导我的代码会发生什么。

public class DBHandler{

private static final String TAG = "DBHandler";

//Field Names
public static final String COLUMN_ID = "_id";
public static final String COLUMN_EVENTTITLE = "eventTitle";
public static final String COLUMN_Date = "date";
public static final String COLUMN_DESTINATION = "destination";
public static final String COLUMN_DURATION = "durationTime";
public static final String COLUMN_ALARMTIME = "alarmTime";
public static final String[] ALL_KEYS = new String[]{COLUMN_ID, COLUMN_EVENTTITLE, COLUMN_Date, COLUMN_DESTINATION, COLUMN_DURATION,COLUMN_ALARMTIME};

//Column Number for each Field Name:
public static final int COL_ID = 0;
public static final int COL_EventTITLE = 1;
public static final int COL_DATE = 2;
public static final int COL_DESTINATION = 3;
public static final int COL_DURATION = 4;
public static final int COL_ALARMTIME = 5;

//Database Info:
private static final int DATABASE_VERSION = 2;
private static final String DATABASE_NAME = "SP";
public static final String TABLE_EVENT = "Event";


//SQL Statament to create database
private static final String DATABASE_CREATE_SQL =
        "CREATE TABLE " + TABLE_EVENT + "(" +
        COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " +
        COLUMN_EVENTTITLE + " TEXT NOT NULL, " +
        COLUMN_Date + " TEXT NOT NULL, " +
        COLUMN_DESTINATION + " TEXT NOT NULL, " +
        COLUMN_DURATION + " TEXT NOT NULL, " +
        COLUMN_ALARMTIME + " TEXT NOT NULL" +
        ");";

private final Context context;
private DatabaseHelper myDBHelper;
private SQLiteDatabase db;


public DBHandler(Context ctx){
    this.context = ctx;
    myDBHelper = new DatabaseHelper(context);
}

public DBHandler open(){
    db = myDBHelper.getWritableDatabase();
    return this;
}

public void close(){
    myDBHelper.close();
}


public long insertEvent(String eventtitle, String date, String destination, String duration, String alarmtime){
    ContentValues contentValues = new ContentValues();
    contentValues.put(COLUMN_EVENTTITLE, eventtitle);
    contentValues.put(COLUMN_Date, date);
    contentValues.put(COLUMN_DESTINATION, destination);
    contentValues.put(COLUMN_DURATION, duration);
    contentValues.put(COLUMN_ALARMTIME, alarmtime);

    //Insert data into database
    return db.insert(TABLE_EVENT, null, contentValues);

}

//Delete a row from the database, by rowid (primary key)
public boolean deleteRow(long rowId){
    String where = COLUMN_ID + "=" + rowId;
    return db.delete(TABLE_EVENT, where, null) != 0;
}

//return all data in database
public Cursor getAllRows(){
    String where = null;
    Cursor c = db.query(true, TABLE_EVENT, ALL_KEYS, where, null, null, null,null, null);
    if(c != null){
        c.moveToFirst();
    }
    return c;
}

//Get a specific row(by rowID)
public Cursor getRow(long rowId){
    String where = COLUMN_ID + "=" + rowId;
    Cursor c = db.query(true, TABLE_EVENT, ALL_KEYS, where, null, null, null, null, null);
    if(c != null){
        c.moveToFirst();
    }
    return c;
}

//Change an existing row to be equal to new data
public boolean updateEvent(long id, String eventtitle, String date, String destination, String duration,String alarmtime ){
    String where = COLUMN_ID + "=" + id;
    ContentValues newValues = new ContentValues();
    newValues.put(COLUMN_EVENTTITLE, eventtitle);
    newValues.put(COLUMN_Date, date);
    newValues.put(COLUMN_DESTINATION, destination);
    newValues.put(COLUMN_DURATION, duration);
    newValues.put(COLUMN_ALARMTIME, alarmtime);

   return db.update(TABLE_EVENT, newValues, where, null) !=0;
}


private static class DatabaseHelper extends SQLiteOpenHelper{
    DatabaseHelper(Context context){
        super(context, TABLE_EVENT, null, DATABASE_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db){
        db.execSQL(DATABASE_CREATE_SQL);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion){
        Log.w(TAG, "Upgrading application's database from version" + oldVersion +
        "to" + newVersion + ", which will destroy all old data!");

        //Destroy old database:
        db.execSQL("DROP TABLE IF EXISTS" + TABLE_EVENT);

        onCreate(db);
    }
}
}

错误：

android.database.sqlite.SQLiteException: no such column: _id (code 1): , while compiling: SELECT DISTINCT _id, eventTitle, date, destination, durationTime, alarmTime FROM Event
            at android.database.sqlite.SQLiteConnection.nativePrepareStatement(Native Method)
            at android.database.sqlite.SQLiteConnection.acquirePreparedStatement(SQLiteConnection.java:1113)
            at android.database.sqlite.SQLiteConnection.prepare(SQLiteConnection.java:690)
            at android.database.sqlite.SQLiteSession.prepare(SQLiteSession.java:588)
            at android.database.sqlite.SQLiteProgram.<init>(SQLiteProgram.java:58)
            at android.database.sqlite.SQLiteQuery.<init>(SQLiteQuery.java:37)
            at android.database.sqlite.SQLiteDirectCursorDriver.query(SQLiteDirectCursorDriver.java:44)
            at android.database.sqlite.SQLiteDatabase.rawQueryWithFactory(SQLiteDatabase.java:1430)
            at android.database.sqlite.SQLiteDatabase.queryWithFactory(SQLiteDatabase.java:1277)
            at android.database.sqlite.SQLiteDatabase.query(SQLiteDatabase.java:1148)
            at com.howard.fyp.DBHandler.getAllRows(DBHandler.java:92)
            at com.howard.fyp.TodayActivity.populateListView(TodayActivity.java:40)
            at com.howard.fyp.TodayActivity.onCreateView(TodayActivity.java:26)
            at android.support.v4.app.Fragment.performCreateView(Fragment.java:1786)
            at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:953)
            at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1136)
            at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:739)
            at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1499)
            at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:456)
            at android.os.Handler.handleCallback(Handler.java:733)
            at android.os.Handler.dispatchMessage(Handler.java:95)
            at android.os.Looper.loop(Looper.java:157)
            at android.app.ActivityThread.main(ActivityThread.java:5356)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1265)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1081)
            at dalvik.system.NativeStart.main(Native Method)

Answer 1

您是否第二次添加了_id列？然后，您必须增加 DATABASE_VERSION 常量值才能使onUpgrade()方法触发。

但是你的onUpgrade()方法无法破坏旧表：

db.execSQL("DROP TABLE IF EXISTS" + TABLE_EVENT);

在表名前需要空格：

db.execSQL("DROP TABLE IF EXISTS " + TABLE_EVENT);

或者，由于旧表仍然存在，因此不会创建新表。

在SQLite数据库中找不到列

1 个答案: