Question

我有一个从资产文件夹中的文件生成的SQLite数据库... 现在我知道无法修改应用程序的资源，但如果我发布更新的应用程序，我希望已经创建的数据库将被清除并从新版本的应用程序中包含的新资产文件数据库中重新创建

这是我的数据库助手类

public class DataBaseHelper extends SQLiteOpenHelper {
    private static String TAG = "DataBaseHelper"; // Tag just for the LogCat
                                                    // window
    // destination path (location) of our database on device
    private static String DB_PATH = "";
    private static String DB_NAME = "";// Database name
    private SQLiteDatabase mDataBase;
    private final Context mContext;

    public DataBaseHelper(Context context, String nomeDB) {
        super(context, nomeDB, null, 2);// 2 is the Database Version
        DB_NAME = nomeDB;
        DB_PATH = "/data/data/" + context.getPackageName() + "/databases/";
        this.mContext = context;
    }

    public void createDataBase() throws IOException {
        // If database not exists copy it from the assets

        boolean mDataBaseExist = checkDataBase();
        if (!mDataBaseExist) {
            this.getReadableDatabase();
            this.close();
            try {
                // Copy the db from assests
                copyDataBase();
                Log.e(TAG, "createDatabase database created");
            } catch (IOException mIOException) {
                Log.e(TAG, mIOException.toString());
                throw mIOException;
            }
        }
    }

    private boolean checkDataBase() {
        File dbFile = new File(DB_PATH + DB_NAME);
        // Log.v("dbFile", dbFile + "   "+ dbFile.exists());
        return dbFile.exists();
    }

    // Copy DB from assests
    private void copyDataBase() throws IOException {
        InputStream mInput = mContext.getAssets().open(DB_NAME);
        String outFileName = DB_PATH + DB_NAME;
        OutputStream mOutput = new FileOutputStream(outFileName);
        byte[] mBuffer = new byte[1024];
        int mLength;
        while ((mLength = mInput.read(mBuffer)) > 0) {
            mOutput.write(mBuffer, 0, mLength);
        }
        mOutput.flush();
        mOutput.close();
        mInput.close();
    }

    public boolean openDataBase() throws SQLException {
        String mPath = DB_PATH + DB_NAME;
        mDataBase = SQLiteDatabase.openDatabase(mPath, null,
                SQLiteDatabase.CREATE_IF_NECESSARY);
        return mDataBase != null;
    }

    @Override
    public synchronized void close() {
        if (mDataBase != null)
            mDataBase.close();
        super.close();
    }

    @Override
    public void onCreate(SQLiteDatabase arg0) {
        // TODO Auto-generated method stub

    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // TODO Auto-generated method stub

    }

}

该行

super(context, nomeDB, null, 2);// 2 is the Database Version

如果已经存在的DB具有以前必须更新的版本号

，则应标识版本广告

所以如果我将发布一个带有DB版本3的新应用程序

super(context, nomeDB, null, 3);

应用程序必须从应用程序的新编译版本中包含的资产重新创建数据库。

但我不知道这样做的正确方法。

Answer 1

您需要使用onCreate（）和onUpdate（）的内置生命周期方法。

这样的事情：

public class DataBaseHelper extends SQLiteOpenHelper {
    private static String TAG = "DataBaseHelper"; // Tag just for the LogCat
                                                    // window
    // destination path (location) of our database on device
    private static final int    DATABASE_VERSION = 3;
    private static String DB_PATH = "";
    private static String DB_NAME = "";// Database name
    private SQLiteDatabase mDataBase;
    private final Context mContext;

    public DataBaseHelper(Context context, String nomeDB) {
        super(context, nomeDB, null, DATABASE_VERSION);
        DB_NAME = nomeDB;
        DB_PATH = "/data/data/" + context.getPackageName() + "/databases/";
        this.mContext = context;
    }

    // Copy DB from assests
    private void copyDataBase() throws IOException {
        InputStream mInput = mContext.getAssets().open(DB_NAME);
        String outFileName = DB_PATH + DB_NAME;
        OutputStream mOutput = new FileOutputStream(outFileName);
        byte[] mBuffer = new byte[1024];
        int mLength;
        while ((mLength = mInput.read(mBuffer)) > 0) {
            mOutput.write(mBuffer, 0, mLength);
        }
        mOutput.flush();
        mOutput.close();
        mInput.close();
    }

    public boolean openDataBase() throws SQLException {
        String mPath = DB_PATH + DB_NAME;
        mDataBase = SQLiteDatabase.openDatabase(mPath, null,
                SQLiteDatabase.CREATE_IF_NECESSARY);
        return mDataBase != null;
    }

    @Override
    public synchronized void close() {
        if (mDataBase != null)
            mDataBase.close();
        super.close();
    }

    /**
     * This method is called when the app doesn't have a database and a new one needs to be created
     */
    @Override
    public void onCreate(SQLiteDatabase arg0) {
        try {
            // Copy the db from assests
            copyDataBase();
            Log.e(TAG, "database created");
        } catch (IOException mIOException) {
            Log.e(TAG, mIOException.toString());
            throw mIOException;
        }
   }

    /**
     * This method is called when the app's database version is < the value passed into the constructor
     */
    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        try {
            // delete existing?

            // Copy the db from assests
            copyDataBase();
            Log.e(TAG, "database updated");
        } catch (IOException mIOException) {
            Log.e(TAG, mIOException.toString());
            throw mIOException;
        }
    }

}

Answer 2

您可以使用android-sqlite-asset-helper更新数据库或指向最新版本

https://github.com/jgilfelt/android-sqlite-asset-helper

从Assets Folder更新问题创建的SQLite DB

2 个答案: