Question

不知怎的，我在Log中复制.db文件时遇到错误（如您在代码中看到的那样） napoleon.db文件位于assets文件夹中，因此我认为一切都应该有效，但它并没有

为什么没有找到它？

我是通过示例来做的，但它并不起作用。有什么想法吗？

public class MySqLiteOpenHelper extends SQLiteOpenHelper{
    private static String DATABASE_NAME = "napoleon.db";
    public final static String DATABASE_PATH = "/data/data/com.example.task/databases/";
    private static final int DATABASE_VERSION = 1;

    private SQLiteDatabase dataBase;
    private final Context dbContext;

    public MySqLiteOpenHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
        this.dbContext = context;
        // checking database and open it if exists
        if (checkDataBase()) {
            openDataBase();
        } else
        {
            try {
                this.getReadableDatabase();
                copyDataBase();
                this.close();
                openDataBase();

            } catch (IOException e) {
                throw new Error("Error copying database");
            }
            Toast.makeText(context, "Initial database is created", Toast.LENGTH_LONG).show();
        }
    }

    private void copyDataBase() throws IOException{
        InputStream myInput = dbContext.getAssets().open(DATABASE_NAME);
        String outFileName = DATABASE_PATH + DATABASE_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();
    }

    public void openDataBase() throws SQLException {
        String dbPath = DATABASE_PATH + DATABASE_NAME;
        dataBase = SQLiteDatabase.openDatabase(dbPath, null, SQLiteDatabase.OPEN_READWRITE);
    }

    private boolean checkDataBase() {
        SQLiteDatabase checkDB = null;
        boolean exist = false;
        try {
            String dbPath = DATABASE_PATH + DATABASE_NAME;
            checkDB = SQLiteDatabase.openDatabase(dbPath, null,
                    SQLiteDatabase.OPEN_READONLY);
        } catch (SQLiteException e) {
            Log.v("MyLog", "database does't exist");
        }

        if (checkDB != null) {
            exist = true;
            checkDB.close();
        }
        return exist;
    }

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

    }

    @Override
    public void onUpgrade(SQLiteDatabase arg0, int arg1, int arg2) {
        // TODO Auto-generated method stub

    }
}

Answer 1

您应该使用此DB路径：

if(android.os.Build.VERSION.SDK_INT >= 17){
   DB_PATH = context.getApplicationInfo().dataDir + "/databases/";         
}
else
{
   DB_PATH = "/data/data/" + context.getPackageName() + "/databases/";
}

对于Jellybean 4.2多用户更改：

DB_PATH = "/data/data/" + context.getPackageName() + "/databases/";

为：

DB_PATH = context.getApplicationInfo().dataDir + "/databases/";

Answer 2

使用以下帖子逐行学习将数据库从资产复制到应用程序内存

http://iamvijayakumar.blogspot.in/2013/11/copy-sqlite-database-file-from-assets.html

从资产打开SQLite .db

2 个答案: