Question

我正在制作一个问答游戏，我想使用SQLite数据库，我将存储300多个问题并随机选择其中一个。我做了一个研究，我知道如何创建和更新表，如何添加，修改和删除Android应用程序中的行，但我找不到一种方法将我的应用程序连接到已经完成的数据库（存储的只读数据库）在resources（assets）文件夹中。）

你能帮我吗？

Answer 1

这是一个非常复杂的事情，好吧不是很复杂，但你必须做一些编程的东西。要直接从资产文件夹中读取数据库，您必须将其复制到内部存储或SD卡。在这里解释一下，请阅读本教程，这是正确的开始：

http://zaman91.wordpress.com/2010/09/22/android-how-to-use-own-sqlite-database/

Answer 2

您应该将资源文件夹中的数据库文件复制到已安装的应用程序中例如：

public class DatabaseOpenHelper extends SQLiteOpenHelper {

private final static String DB_NAME = "YourDatabaseFile.sqlite";
private static String DB_PATH = "/data/data/%s/databases/";
private final String ERROR_TAG = "error";
private final static int DB_VERSION = 1;
private final int BUFFER_SIZE = 8 * 1024;
private SQLiteDatabase databaseHandle;

private final Context context;

public DatabaseOpenHelper(Context context) {
    super(context, DB_NAME, null, DB_VERSION);

    this.context = context;
    DB_PATH = String.format(DB_PATH, context.getPackageName());
}

public SQLiteDatabase openDataBase() {
    try {
        String databasePath = DB_PATH + DB_NAME;
        if (databaseHandle == null) {
            createDataBase();
            databaseHandle = SQLiteDatabase.openDatabase(databasePath, null, SQLiteDatabase.OPEN_READWRITE);
        }
    }
    catch (SQLiteException e) {
        throw new IllegalStateException(context.getResources().getString(R.string.err_opening_db), e);
    }
    return databaseHandle;
}

private boolean createDataBase() {
    try {
        if (!isDataBase()) {
            this.getReadableDatabase();
            copyDataBase();
            return true;
        }
    }
    catch (SQLiteException e) {
        throw new IllegalStateException(context.getResources().getString(R.string.err_opening_db), e);
    }
    catch (IOException e){
        Log.e(ERROR_TAG, context.getResources().getString(R.string.err_close_stream), e);
    }

    return false;
}

public boolean isDataBase() {
    SQLiteDatabase verifiableDatabase = null;
    try {
        String databasePath = DB_PATH + DB_NAME;
        verifiableDatabase = SQLiteDatabase.openDatabase(databasePath, null, SQLiteDatabase.OPEN_READONLY);
        verifiableDatabase.close();
    }
    catch (SQLiteException e) {
        Log.e(ERROR_TAG, context.getResources().getString(R.string.err_opening_db), e);
        return false;
    }

    return true;
}

private void copyDataBase() throws IOException {
    InputStream externalDbStream = null;
    OutputStream localDbStream = null;
    try {
        externalDbStream = context.getAssets().open(DB_NAME);
        localDbStream = new FileOutputStream(DB_PATH+DB_NAME);

        byte[] buffer = new byte[BUFFER_SIZE];
        int bytesRead;

        while ((bytesRead = externalDbStream.read(buffer)) > 0) {
            localDbStream.write(buffer, 0, bytesRead);
        }
    }
    catch (IOException e) {
        throw new IllegalStateException(context.getResources().getString(R.string.err_copying_db), e);
    }
    finally {
        if (localDbStream != null)
            localDbStream.close();
        if (externalDbStream != null)
            externalDbStream.close();
    }
}

@Override
public void close() {
    databaseHandle.close();
}

@Override
public void onCreate(SQLiteDatabase db) {
}

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

使用：
DatabaseOpenHelper dbHelper = new DatabaseOpenHelper(context); SQLiteDatabase database = dbHelper.openDataBase();

用于测验游戏的Android SQLite数据库

2 个答案: