SQLite 数据从版本 0 迁移到 1

Question

之前我使用db = openOrCreateDatabase("LOCALTILEDB", Context.MODE_PRIVATE, null); 创建了一个数据库，它正在创建一个版本为“0”的数据库。

在下一个版本的应用程序中，我正在使用 SQLiteOpenHelper 类，其中 OnUpgrade 方法显示调用的错误，数据库版本不能为 '0'。

所以请任何人帮助我将数据从我的 0 版本数据库迁移到版本 1 数据库。

Answer 1

在使用 SQLiteOpenHelper 扩展的类中，将 super(context, DATABASE_NAME, null, DATABASE_VERSION) 传递给默认构造函数。例如。

public class MyDBHelper extends SQLiteOpenHelper {

// Database Version
private static final int DATABASE_VERSION = 1;

// Database Name
private static final String DATABASE_NAME = "MyDb";


public MyDBHelper(Context context) {
    super(context, DATABASE_NAME, null, DATABASE_VERSION);
}

@Override
public void onCreate(SQLiteDatabase aSqLiteDatabase) {

}  @Override
public void onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1) {

} 

}

Answer 2

我怀疑您所做的是编写通过 super 传递的 0 版本，例如:-

public static final int DBVERSION = 0;

public SO46316125DBHlpr(Context context) {
    super(context, DBNAME, null, DBVERSION);
}

这将导致包含Version must be >= 1, was 0的异常

例如:-

09-20 21:16:40.631 1840-1840/mjt.soqanda E/AndroidRuntime: FATAL EXCEPTION: main
                                                           Process: mjt.soqanda, PID: 1840
                                                           java.lang.RuntimeException: Unable to start activity ComponentInfo{mjt.soqanda/mjt.soqanda.MainActivity}: java.lang.IllegalArgumentException: Version must be >= 1, was 0
                                                               at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2325)
                                                               at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)
                                                               at android.app.ActivityThread.access$800(ActivityThread.java:151)
                                                               at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
                                                               at android.os.Handler.dispatchMessage(Handler.java:102)
                                                               at android.os.Looper.loop(Looper.java:135)
                                                               at android.app.ActivityThread.main(ActivityThread.java:5254)
                                                               at java.lang.reflect.Method.invoke(Native Method)
                                                               at java.lang.reflect.Method.invoke(Method.java:372)
                                                               at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
                                                               at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
                                                            Caused by: java.lang.IllegalArgumentException: Version must be >= 1, was 0
                                                               at android.database.sqlite.SQLiteOpenHelper.<init>(SQLiteOpenHelper.java:99)
                                                               at android.database.sqlite.SQLiteOpenHelper.<init>(SQLiteOpenHelper.java:77)
                                                               at mjt.soqanda.SO46316125DBHlpr.<init>(SO46316125DBHlpr.java:23)

但是，简单地编写一个非零的正版本，将其传递给 super 方法，然后将导致使用该版本。

---

例如我已将数据库设置为版本 0（使用 PRAGMA user_version=0，然后是 PRAGMA user_version（检索版本）并具有：-

09-20 21:29:35.117 19172-19172/? D/DBVERSION: The Database User Version is 1
09-20 21:29:35.118 19172-19172/? D/CHGDBVERSION: Attempting to alter DB Version from 1 to new version 0
09-20 21:29:35.152 19172-19172/? D/CHGDBVERSION: DB Version changed successfully, DB Version is now 0

然后我使用版本 100：-

public static final int DBVERSION = 100;

public SO46316125DBHlpr(Context context) {
    super(context, DBNAME, null, DBVERSION);
}

所以这会直接跳转到版本 100（onUpgrade 方法为空）：-

09-20 21:35:45.344 27937-27937/mjt.soqanda D/DBVERSION: The Database User Version is 100

当然 1 也可以。

---

为了测试/生产上述内容，我使用了以下方法：-

public void showDBVersion() {
    SQLiteDatabase db = this.getWritableDatabase();
    Cursor csr = db.rawQuery("PRAGMA user_version",null);
    if (csr.moveToFirst()) {
        Log.d("DBVERSION","The Database User Version is " + csr.getString(0));
    }
}


public int alterDBVersion(SQLiteDatabase db, int fromversion, int toversion) {

    int current_version = -1;
    int changed_version = -1;

    Cursor csr = db.rawQuery("PRAGMA user_version;",null);
    if (csr.moveToFirst()) {
        current_version = csr.getInt(0);
    } else {
        Log.d("CHGDBVERSION","Unable to get the current version.");
        return current_version;
    }

    if (current_version == fromversion) {
        Log.d("CHGDBVERSION","Attempting to alter DB Version from " +
                Integer.toString(fromversion) +
                " to new version " +
                Integer.toString(toversion)
        );
        db.rawQuery("PRAGMA user_version=" + Integer.toString(toversion) + ";",null); //NOTE 1
        db.execSQL("PRAGMA user_version=" + Integer.toString(toversion) + ";");
    }

    csr = db.rawQuery("PRAGMA user_version;",null);
    if (csr.moveToFirst()) {
        changed_version = csr.getInt(0);
    } else {
        Log.d("CHGDBVERSION","Unable to get the new/changed version.");
        return -2;
    }
    if (current_version != fromversion || changed_version != toversion) {
        Log.d("CHGDBVERSION",
                "DB Version was not changed as requested. Version is now " +
                        Integer.toString(changed_version));
        return -3;
    } else {
        Log.d("CHGDBVERSION","DB Version changed successfully, DB Version is now " +
        Integer.toString(changed_version));
    }
    return 0;
}

注意 1 不起作用必须按照Android: PRAGMA statements that set data don't work 使用 execSQL

在MainActivity中使用以下代码

    SO46316125DBHlpr dbhlpr = new SO46316125DBHlpr(this);
    dbhlpr.showDBVersion();
    dbhlpr.alterDBVersion(dbhlpr.getWritableDatabase(),1,0);

明显改变参数（第一个是要更改的版本，因此当前版本必须匹配它，第二个是要更改到的版本，如果第一个匹配）。以上示例将版本 1 更改为版本 0。