如何正确使用Android中预装的数据库

Question

I want to use preloaded database. The database must be annexed to the application, and then be able to update. I have a number of doubts about how to connect it to avoid problems. I ask that answered professionals who deal with the problem. Thank you.

1. If my base is greater than 1 MB, it pops up an error D / asset (909): Data exceeds UNCOMPRESS_DATA_MAX. Can be broken down into pieces smaller than 1 megabyte, and can be changed to increase (". Jpg", ". Jpeg", ". Png", ". Gif", ". wav", ". mp2", ". mp3", ". ogg", ". aac", ". mpg", ". mpeg", ". mid", ". midi", ". smf", ". jet", ". rtttl", ". imy", ". xmf", ". mp4", ". m4a", ". m4v", ".3 gp", ".3 gpp", ".3 g2", ".3 gpp2", ". amr", ". awb", ". wma", ". wmv"). Which option is better (easier - change the extension).

2. Might fail "No such table android_metadata" but I added manually to the database en_US, but what if the application multilanguage?

3. When reading the database, I use the method mDb = getReadableDatabase ();, but I'm at the end of a close reading - mDb.close (); As they say on the Internet may not care any error Unable to open database file. This is especially for the devices HTC.

The following quote code

public class QuestionsDbAdapter extends SQLiteOpenHelper {

private String DATABASE_PATH = "/data/data/YOUR_PACKAGE/";
public static final String DATABASE_NAME = "mantestQuestions";

public static final String TABLE_QUESTIONS = "Questions";
public static final String QUESTIONS_COLUMN_ID = "_id";
public static final String QUESTIONS_COLUMN_QUESTION ="Question";

public static final String TABLE_ANSWERS = "Answers";
public static final String ANSWERS_COLUMN_ID = "_id";
public static final String ANSWERS_COLUMN_QUESTION_ID = "QuestionId";
public static final String ANSWERS_COLUMN_ANSWER = "Answer";
public static final String ANSWERS_COLUMN_POINT = "Point";

private SQLiteDatabase mDb;

private final Context mContext;

private boolean mCreateDatabase = false;
private boolean mUpgradeDatabase = false;

/**
 * Constructor
 * Takes and keeps a reference of the passed context in order to access
 * the application's assets and resources
 * @param context
 */
public QuestionsDbAdapter(Context context) {
    super(context, DATABASE_NAME, null, context.getResources().getInteger(R.integer.questionDbVersion));

    mContext = context;
}

public void initializeDatabase(String path) {
    DATABASE_PATH = path;
    getWritableDatabase();

    if(mUpgradeDatabase) {
        mContext.deleteDatabase(DATABASE_NAME);
    }

    if(mCreateDatabase || mUpgradeDatabase) {
        try {
            copyDatabase();
        } catch (IOException e) {
            throw new Error("Error copying database");
        }
    }
}

private void copyDatabase() throws IOException {
    close();

    InputStream input = mContext.getAssets().open(DATABASE_NAME);

    String outFileName = DATABASE_PATH + DATABASE_NAME;

    OutputStream output = new FileOutputStream(outFileName);

    // Transfer bytes from the input file to the output file
    byte[] buffer = new byte[1024];
    int length;
    while ((length = input.read(buffer)) > 0) {
        output.write(buffer, 0, length);
    }

    output.flush();
    output.close();
    input.close();

    getWritableDatabase().close();
}

public QuestionsDbAdapter open() throws SQLException {
    mDb = getReadableDatabase();
    return this;
}

public void CleanUp() {
    mDb.close();
}

@Override
public void onCreate(SQLiteDatabase db) {
    mCreateDatabase = true;
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    mUpgradeDatabase = true;
}

/**
 * Public helper methods
 */

public Cursor getQuestionById(long rowId) throws SQLException {
    Cursor cursor = mDb.query(true, TABLE_QUESTIONS,
            new String[] { QUESTIONS_COLUMN_ID, QUESTIONS_COLUMN_QUESTION }, QUESTIONS_COLUMN_ID + "=" + rowId,
            null, null, null, null, null);

    return cursor;
}

public Cursor getAnswerById(long rowId) throws SQLException {
    Cursor cursor = mDb.query(true, TABLE_ANSWERS,
            new String[] { ANSWERS_COLUMN_ID, ANSWERS_COLUMN_QUESTION_ID, ANSWERS_COLUMN_ANSWER, ANSWERS_COLUMN_POINT },
            ANSWERS_COLUMN_ID + "=" + rowId,
            null, null, null, null, null);

    return cursor;
}

public Cursor getAnswersByQuestionId(long questionId) throws SQLException {
    Cursor cursor = mDb.query(true, TABLE_ANSWERS, new String[] {ANSWERS_COLUMN_ANSWER, ANSWERS_COLUMN_POINT},
            ANSWERS_COLUMN_QUESTION_ID + "=" + questionId, null, null, null, null, null);

    return cursor;
}

public long getCount() {
    String sql = "SELECT COUNT(*) FROM " + TABLE_QUESTIONS;
    SQLiteStatement statement = mDb.compileStatement(sql);
    long count = statement.simpleQueryForLong();
    return count;
}
}

Answer 1

这里不需要这个混乱的代码是Android SQLiteAssetHelper的好方法

Answer 2

我认为问题是你只需要将你的图像存储在移动应用程序中，但如果它的大小非常大，那么从服务器检索它，感谢@confucius对于这篇文章它确实有帮助，这里是另一个循序渐进的教程，解释了如何使用sqlite浏览器在android中制作预加载的数据库