Question

我在表格中添加了一列（SUM）。我认为我需要做的就是重写/重新创建我的表格，增加DATABASE_VERSION的变量，但这不起作用。我的onUpgrade()方法中是否需要一些内容？

版本变量：

private static final int DATABASE_VERSION = 3;

构造

public DatabaseHelper(Context context) { 
    super(context, DB_NAME, null, DATABASE_VERSION); 
}

onUpgrade（）和onCreate（）方法：

 public void onCreate(SQLiteDatabase db) {
    db.execSQL("CREATE TABLE " + TABLE + " ("
            + RANK + " INTEGER PRIMARY KEY AUTOINCREMENT,"
            + SCORE + " LONG,"
            + PERCENTAGE + " INTEGER,"
            + SUM + " LONG"
            + ");");
}

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

LogCat输出

01-04 02:00:24.635: E/AndroidRuntime(6224): FATAL EXCEPTION: main
01-04 02:00:24.635: E/AndroidRuntime(6224): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.test/com.example.test.Results}: android.database.sqlite.SQLiteException: no such column: sum (code 1): , while compiling: SELECT sum FROM HighscoresList
01-04 02:00:24.635: E/AndroidRuntime(6224):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
01-04 02:00:24.635: E/AndroidRuntime(6224):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
01-04 02:00:24.635: E/AndroidRuntime(6224):     at android.app.ActivityThread.access$600(ActivityThread.java:141)
01-04 02:00:24.635: E/AndroidRuntime(6224):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
01-04 02:00:24.635: E/AndroidRuntime(6224):     at android.os.Handler.dispatchMessage(Handler.java:99)
01-04 02:00:24.635: E/AndroidRuntime(6224):     at android.os.Looper.loop(Looper.java:137)
01-04 02:00:24.635: E/AndroidRuntime(6224):     at android.app.ActivityThread.main(ActivityThread.java:5039)
01-04 02:00:24.635: E/AndroidRuntime(6224):     at java.lang.reflect.Method.invokeNative(Native Method)
01-04 02:00:24.635: E/AndroidRuntime(6224):     at java.lang.reflect.Method.invoke(Method.java:511)
01-04 02:00:24.635: E/AndroidRuntime(6224):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
01-04 02:00:24.635: E/AndroidRuntime(6224):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
01-04 02:00:24.635: E/AndroidRuntime(6224):     at dalvik.system.NativeStart.main(Native Method)
01-04 02:00:24.635: E/AndroidRuntime(6224): Caused by: android.database.sqlite.SQLiteException: no such column: sum (code 1): , while compiling: SELECT sum FROM HighscoresList
01-04 02:00:24.635: E/AndroidRuntime(6224):     at android.database.sqlite.SQLiteConnection.nativePrepareStatement(Native Method)
01-04 02:00:24.635: E/AndroidRuntime(6224):     at android.database.sqlite.SQLiteConnection.acquirePreparedStatement(SQLiteConnection.java:882)
01-04 02:00:24.635: E/AndroidRuntime(6224):     at android.database.sqlite.SQLiteConnection.prepare(SQLiteConnection.java:493)
01-04 02:00:24.635: E/AndroidRuntime(6224):     at android.database.sqlite.SQLiteSession.prepare(SQLiteSession.java:588)
01-04 02:00:24.635: E/AndroidRuntime(6224):     at android.database.sqlite.SQLiteProgram.<init>(SQLiteProgram.java:58)
01-04 02:00:24.635: E/AndroidRuntime(6224):     at android.database.sqlite.SQLiteQuery.<init>(SQLiteQuery.java:37)
01-04 02:00:24.635: E/AndroidRuntime(6224):     at android.database.sqlite.SQLiteDirectCursorDriver.query(SQLiteDirectCursorDriver.java:44)
01-04 02:00:24.635: E/AndroidRuntime(6224):     at android.database.sqlite.SQLiteDatabase.rawQueryWithFactory(SQLiteDatabase.java:1314)
01-04 02:00:24.635: E/AndroidRuntime(6224):     at android.database.sqlite.SQLiteDatabase.rawQuery(SQLiteDatabase.java:1253)
01-04 02:00:24.635: E/AndroidRuntime(6224):     at com.example.test.DatabaseHelper.check(DatabaseHelper.java:82)
01-04 02:00:24.635: E/AndroidRuntime(6224):     at com.example.test.Results.showResults(Results.java:111)
01-04 02:00:24.635: E/AndroidRuntime(6224):     at com.example.test.Results.onCreate(Results.java:60)
01-04 02:00:24.635: E/AndroidRuntime(6224):     at android.app.Activity.performCreate(Activity.java:5104)
01-04 02:00:24.635: E/AndroidRuntime(6224):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
01-04 02:00:24.635: E/AndroidRuntime(6224):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
01-04 02:00:24.635: E/AndroidRuntime(6224):     ... 11 more

Answer 1

您的onUpgrade()方法为空：

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

在最基本的级别，您需要添加代码以删除现有表并调用onCreate()，然后再次增加DATABASE_VERSION。

private static final int DATABASE_VERSION = 4; 
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    db.exec("DROP TABLE IF EXISTS " + TABLE);
    onCreate(db);
}

Answer 2

是的，在onUpgrade中您需要实际更新表格，即添加列：

public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    if (oldVersion < 3) {
        db.execSQL("ALTER TABLE " + TABLE + " ADD COLUMN " + SUM + " LONG");
    }
}

如果需要/需要，您可能还需要返回并填充每行的有效“sum”值。

Answer 3

您需要在onUpgrade中重新创建表格：

public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {}
    db.execSQL("DROP TABLE IF EXISTS " + TABLE);
    onCreate(db);
}

或者添加列：

public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {}
    db.execSQL("ALTER TABLE " + TABLE + " ADD COLUMN `SUM` LONG");
}

Answer 4

您需要实现onUpgrade方法并执行必要的表更改。

如果您需要保留现有数据（或者想采用“正确”方法），则应执行ALTER TABLE语句以添加新列，并可能标识默认值或使用正确的值更新现有行。与“Tomas”相同。

以下是一个例子：

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion)
{
    Log.d(TAG, "Upgrading database from version " + oldVersion + " to version  " + newVersion);

    if (newVersion == 3)
    {
        //Moved IO configuration data into flat file, so removing servicedata table.
        db.execSQL(DB_DROP_SERVICEDATA_V3);
    }
    else if (newVersion == 2)
    {
        db.execSQL(DB_ALTER_MESSAGE_V2);
    }
    else
    {
        db.execSQL("drop table if exists " + TABLE_ACCOUNT);
        db.execSQL("drop table if exists " + TABLE_MESSAGE);
        //Old table just checking.
        db.execSQL("drop table if exists servicedata");

        onCreate(db);
    }
}

Answer 5

是的，这就是onUpgrade()的用途。

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

    if (oldVersion < 3) {
        upgradeToVersion3();
    }

    // good pattern is to make these incremental updates to ensure that everyone
    // will end up with the same version no matter what version he/she has now
    if (oldVersion < 4) {
        // upgradeToVersion4()
    }

}

private void upgradeToVersion3() {
    db.execSQL("alter table " + TABLE + " add column SUM LONG");
}

onUpgrade（）未被调用 - Android

5 个答案: