Question

我对onUpgrade有点困惑。我正在开发我的应用程序，在开发过程中，我确实改变了DATABASE_VERSION五次，所以它现在是6。

一切顺利，直到我从手机上完全卸载应用程序并再次构建它。从那时起，我遇到了错误，我要求的所有桌子都没有......

我认为现在，当项目中的DATABASE_VERSION设置为6并且新安装的应用程序在开始时将其设置为6时，onUpgrade()不会被调用。

问题是如何在onUpgrade方法中为新的instalations提供我设置的所有查询？

我知道无论onUpgrade()被调用，都会调用getWritableDatabase()。但是我的应用程序在这条道路上崩溃了：

Cursor spinner_cursor = db.rawQuery("SELECT value1 AS _id, value2 FROM tab2", null);

前面是lane：

SQLiteDatabase db = new DBHelper(this).getWritableDatabase();

我在logCat中收到此错误：

no such table: car (code 1): , while compiling: SELECT value1 AS _id, value2 FROM tab2

我的DBHelper.class看起来像

public class DBHelper extends SQLiteOpenHelper {

private static final String DATABASE_NAME = "DataBase1";
private static final int DATABASE_VERSION = 6; 
private static final String CREATE_QUERY =
        "CREATE TABLE tab1 (id, value1, value2, etc)";

private static final String QUERY_2 =
        "CREATE TABLE tab2 (id, value1, value2, etc)";

private static final String QUERY_3 =
        "CREATE TABLE tab3 (id, value1, value2, etc)";

private static final String QUERY_4 =
        "ALTER TABLE tab2 ADD COLUMN value3 VARCHAR(10) NULL";

private static final String QUERY_5 =
        "ALTER TABLE tab2 ADD COLUMN value4 VARCHAR(10) NULL";

private static final String QUERY_6 =
        "ALTER TABLE tab2 ADD COLUMN value5 VARCHAR(10) NULL";

private static final String QUERY_7 =
        "ALTER TABLE tab3 ADD COLUMN value3 VARCHAR(10) NULL"; 

private static final String QUERY_8 =
        "ALTER TABLE tab3 ADD COLUMN value4 VARCHAR(10) NULL";

private static final String QUERY_9 =
        "ALTER TABLE tab3 ADD COLUMN value5 VARCHAR(10) NULL"; 

private static final String QUERY_10 =
        "ALTER TABLE tab3 ADD COLUMN value6 VARCHAR(10) NULL"; 

private static final String QUERY_11 =
        "ALTER TABLE tab3 ADD COLUMN value7 VARCHAR(10) NULL"; 

private static final String QUERY_12 =
        "DROP TABLE tab3";

private static final String QUERY_13 =
        "CREATE TABLE tab3 (id, value1, value2, etc)";


public DBHelper(Context context){

    super(context, DATABASE_NAME, null, DATABASE_VERSION);
    Log.e("DATABASE OPERATIONS", "Database created / opened");
}

@Override
public void onCreate(SQLiteDatabase db) {

    db.execSQL(CREATE_QUERY);
}

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

    if (oldVersion < 3) {
        db.execSQL(QUERY_2);
        db.execSQL(QUERY_3);
        db.execSQL(QUERY_4);
        db.execSQL(QUERY_5);
        db.execSQL(QUERY_6);
    }

    if (oldVersion < 4) {
        db.execSQL(QUERY_7);
        db.execSQL(QUERY_8);
        db.execSQL(QUERY_9);
        db.execSQL(QUERY_10);
    }

    if (oldVersion < 5){
        db.execSQL(QUERY_11);
    }

    if (oldVersion < 6){
        db.execSQL(QUERY_12);
        db.execSQL(QUERY_13);
    }

提前致谢！

Answer 1

@Override
public void onCreate(SQLiteDatabase db) {

     db.execSQL(CREATE_QUERY);
     db.execSQL(QUERY_2);
     db.execSQL(QUERY_3);
     db.execSQL(QUERY_4);
     db.execSQL(QUERY_5);
     db.execSQL(QUERY_6);
     db.execSQL(QUERY_7);
     db.execSQL(QUERY_8);
     db.execSQL(QUERY_9);
     db.execSQL(QUERY_10);
     db.execSQL(QUERY_11);
     db.execSQL(QUERY_12);
     db.execSQL(QUERY_13);

}

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

    if (oldVersion < 3) {
        db.execSQL(QUERY_2);
        db.execSQL(QUERY_3);
        db.execSQL(QUERY_4);
        db.execSQL(QUERY_5);
        db.execSQL(QUERY_6);
    }

    if (oldVersion < 4) {
        db.execSQL(QUERY_7);
        db.execSQL(QUERY_8);
        db.execSQL(QUERY_9);
        db.execSQL(QUERY_10);
    }

    if (oldVersion < 5){
        db.execSQL(QUERY_11);
    }

    if (oldVersion < 6){
        db.execSQL(QUERY_12);
        db.execSQL(QUERY_13);
    }

在新安装的应用程序上的onUpgrade（）

1 个答案: