java - 永远不会调用数据库 onUpgrade 方法

Question

我正在尝试将我的数据库从版本 1 升级到版本 2。我正在分配 DATABASE_VERSION = 2(也分配了第一个版本)但从未调用过 onUpgrade .可能代码中有明显的错误，但我看不到它，因为我已经尝试解决这个问题很长时间了。

下面是数据库助手类的代码:

public class DatabaseHelper extends SQLiteOpenHelper {

    private static final int DATABASE_VERSION = 2;
    public static String DB_PATH;
    public static String DB_NAME = "db.sqlite3";
    public SQLiteDatabase database;
    public final Context context;

    public DatabaseHelper(Context context) {
        super(context, DB_NAME, null, DATABASE_VERSION);
        this.context = context;

        File direct = new File(Environment.getExternalStorageDirectory()
                + "/.test");
        if (!direct.exists()) {
            if (direct.mkdir())
                ;
        }
        DB_PATH = Environment.getExternalStorageDirectory().getPath()
                + "/.test/";
    }

    public void createDataBase() {
        boolean dbExist = checkDataBase();
        if (!dbExist) {
            try {
                copyDataBase();
            } catch (IOException e) {
                Log.e(this.getClass().toString(), "Copying error");
                throw new Error("Error copying database!");
            }
        }
    }

    private boolean checkDataBase() {
        SQLiteDatabase checkDb = null;
        try {
            String path = DB_PATH + DB_NAME;
            checkDb = SQLiteDatabase.openDatabase(path, null,
                    SQLiteDatabase.OPEN_READONLY);
        } catch (SQLException e) {
            Log.e(this.getClass().toString(), "Error while checking db");
        }
        if (checkDb != null) {
            checkDb.close();
        }
        return checkDb != null;
    }

    private void copyDataBase() throws IOException {
        InputStream externalDbStream = context.getAssets().open(
                "databases/" + DB_NAME);
        String outFileName = DB_PATH + DB_NAME;
        OutputStream localDbStream = new FileOutputStream(outFileName);

        byte[] buffer = new byte[1024];
        int bytesRead;
        while ((bytesRead = externalDbStream.read(buffer)) > 0) {
            localDbStream.write(buffer, 0, bytesRead);
        }
        localDbStream.close();
        externalDbStream.close();
    }

    public SQLiteDatabase openDataBase() throws SQLException {
        String path = DB_PATH + DB_NAME;
        if (database == null) {
            createDataBase();
            database = SQLiteDatabase.openDatabase(path, null,
                    SQLiteDatabase.OPEN_READONLY);
        }
        return database;
    }

    // some unimportant methods

@Override
    public void onCreate(SQLiteDatabase db) {
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        Log.w("myLogs", " --- onUpgrade database --- ");
    }

在 Activity 中我这样调用数据库:

DatabaseHelper dbOpenHelper = new DatabaseHelper(this);
SQLiteDatabase database = dbOpenHelper.openDataBase();

我的错误在哪里？请帮忙。

更新: database.getVersion() 返回 0

---

更新的 openDataBase() 方法(有效):

public SQLiteDatabase openDataBase() throws SQLException {
    String path = DB_PATH + DB_NAME;
    if (database == null) {
        createDataBase();
        database = SQLiteDatabase.openDatabase(path, null,
            SQLiteDatabase.OPEN_READWRITE);
        this.getWritableDatabase();
    }
    return database;
}

Answer 1

本地数据库版本将始终为 0，并且 onUpgrade 不会被调用，因为您从未调用过 getWritableDatabase/getReadableDatabase，这会增加版本并返回本地数据库。

所以你需要:

1. 在您的构造函数/oncreate 中调用getReadableDatabase();，只是为了触发进程，以防数据库版本发生变化
   或
2. 手动检查 sdcard 版本，db.getVersion(); 与当前版本 - DATABASE_VERSION 进行比较。做任何您需要做的事 - 升级或降级。