22

我正在创建一个 Android 应用程序，并在其中使用 sqlite 数据库。为此，我在项目的资产文件夹中放置了一个 sqlite 文件，并且在我第一次使用下面的代码执行应用程序时将此文件复制到手机。

 private void copyDataBase() throws IOException {
    new File(DB_PATH).mkdirs();
    InputStream myInput = appContext.getAssets().open(DB_NAME);
    String outFileName = DB_PATH + DB_NAME;
    OutputStream myOutput = new FileOutputStream(outFileName);
    byte[] buffer = new byte[1024];
    int length;

    while ((length = myInput.read(buffer)) > 0) {
        myOutput.write(buffer, 0, length);
    }

    myOutput.flush();
    myOutput.close();
    myInput.close();
}

但我收到了这个错误。

 09-21 18:03:56.841: E/SQLiteLog(7850): (1) no such table: tbl_player

但该表存在于资产文件中。所以我使用这种方法从手机中获取数据库文件。

public static void exportDB(String databaseName, Context context) {
    try {
        File sd = Environment.getExternalStorageDirectory();
        File data = Environment.getDataDirectory();

        if (sd.canWrite()) {
            String currentDBPath = "//data//" + context.getPackageName()
                    + "//databases//" + databaseName + "";
            String backupDBPath = "sensor_game.db";
            File currentDB = new File(data, currentDBPath);
            File backupDB = new File(sd, backupDBPath);

            if (currentDB.exists()) {
                FileChannel src = new FileInputStream(currentDB)
                        .getChannel();
                FileChannel dst = new FileOutputStream(backupDB)
                        .getChannel();
                dst.transferFrom(src, 0, src.size());
                src.close();
                dst.close();
            }
        }

    } catch (Exception e) {

    }
}

我发现获取的数据库文件中没有表。

注意：此问题仅在、、和中发生OnePlus Two并正常工作Nexus 4Htc 820Moto EGalxy S3Galaxy Quottro

4

3 回答 3

6

不同设备中的数据库路径可能不同。您需要使用Context.getDatabasePath(String)才能获取数据库路径。

例如

File backupDB = context.getDatabasePath(backupDBPath);
于 2015-12-11T14:58:16.713 回答
3

我找到了解决方案，我使用了以下功能：

public void createDb() {
        boolean dbExist = checkDataBase();

        if (dbExist) {
            // do nothing - database already exist
        } else {
            // call close() for properly copy database file
            this.getReadableDatabase().close();
            try {
                copyDataBase();
            } catch (IOException e) {
                e.printStackTrace();
                throw new Error("Error copying database");
            }
        }
    }

根据这篇文章，我们需要打电话close()，您也可以将数据库推送到一加两台设备。

于 2016-02-10T12:21:04.343 回答
3

经过长时间的尝试和搜索，我被迫假设 OP2 制造中应该存在错误，因为它在所有其他设备中都可以正常工作。

我改变了使用查询创建数据库的方法，而不是从资产中复制数据库文件。像下面的代码

import java.io.File;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;

public class MySQLiteHelper extends SQLiteOpenHelper implements DBConstants {

private static MySQLiteHelper mInstance = null;
private SQLiteDatabase myDataBase;
private static String DB_PATH = "";

public MySQLiteHelper(Context context) {
    super(context, DATABASE_NAME, null, DATABASE_VERSION);
    try {
        if (checkDataBase())
            openDataBase();
        else
            myDataBase = this.getReadableDatabase();
    } catch (Exception e) {
    }
}

public static MySQLiteHelper instance(Context context) {

    File outFile = context.getDatabasePath(DATABASE_NAME);
    DB_PATH = outFile.getPath();

    if (mInstance == null) {
        mInstance = new MySQLiteHelper(context);
    }

    return mInstance;
}

private void openDataBase() throws Exception {
    try {
        myDataBase = SQLiteDatabase.openDatabase(DB_PATH, null,
                SQLiteDatabase.OPEN_READWRITE);
    } catch (SQLException e) {
        // TODO: handle exception
    }
}

private boolean checkDataBase() {
    SQLiteDatabase checkDB = null;
    try {
        checkDB = SQLiteDatabase.openDatabase(DB_PATH, null,
                SQLiteDatabase.OPEN_READONLY);

    } catch (SQLiteException e) {
        /** database does't exist yet. */
    } catch (Exception e) {
    }
    if (checkDB != null) {
        checkDB.close();
    }
    return checkDB != null ? true : false;
}

@Override
public void onCreate(SQLiteDatabase db) {

    Log.v("log_tag", "onCreate");
    myDataBase = db;

    // creating a sample table
    String CREATE_DEVICE_TABLE = "CREATE TABLE " + DEVICE + " ("
            + KEY_DEVICEID + " TEXT, " + KEY_OPERATOR + " TEXT, "
            + KEY_DEVICENAME + " TEXT, " + KEY_DEVICETOTALMEMORY
            + " INTEGER, " + KEY_SCREENWIDTH + " INTEGER, "
            + KEY_SCREENHEIGHT + " INTEGER, " + KEY_OPERATINGSYSTEM
            + " TEXT)";

    db.execSQL(CREATE_DEVICE_TABLE);

    // other tables also can be created from here.
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    db.execSQL("DROP TABLE IF EXISTS " + DEVICE);

    // Create tables again (as per requirement)
    this.onCreate(db);
}

public Cursor rawQuery(String qry) {
    return myDataBase.rawQuery(qry, null);
}

public long insert(String tableName, ContentValues cv) {
    return myDataBase.insert(tableName, null, cv);
}

public void insertWithOnConflict(String tableName, ContentValues cv,
        int flag) {
    myDataBase.insertWithOnConflict(tableName, null, cv, flag);

}

public long update(String tableName, ContentValues cv, String whereClose) {
    return myDataBase.update(tableName, cv, whereClose, null);

}

public int deleteData(String table_name, String whereClause) {
    return (int) myDataBase.delete(table_name, whereClause, null);
}

}

它对我有用

谢谢！

于 2015-12-14T06:17:33.253 回答