java - 加载一个小型 SQLite 数据库(20 行左右)以使用 Android 进行读取

Question

我是 Android 开发新手，但我不是业余程序员。我想要获取一个保存在桌面上的数据库中的小型 SQLite 表(我从 CSV 文件导入)，并能够在我的应用程序中访问其内容。我实际上不需要编辑内容，只需从中读取即可。

我在互联网上找到了这个源代码示例，我认为它可以完成这项工作，但它没有按预期工作。它告诉我首先将数据库保存到 Assets 文件夹中。我不知道我是否以正确的方式去做这件事，而且我厌倦了花时间在互联网上搜索。任何帮助将不胜感激!

public class DataBaseHelper extends SQLiteOpenHelper {

    //The Android's default system path of your application database.
    private static String DB_PATH = "/data/data/com.bigapple0208.seth3/databases/";
    private static String DB_NAME = "bigapple0208database"; 
    private SQLiteDatabase myDataBase;  
    private final Context myContext;

    /**
     * Constructor
     * Takes and keeps a reference of the passed context in order to access to the application assets and resources.
     * @param context
     */
    public DataBaseHelper(Context context) {
        super(context, DB_NAME, null, 1);
        this.myContext = context;
    }   

    /**
     * Creates a empty database on the system and rewrites it with your own database.
     **/
    public void createDataBase() throws IOException{
        boolean dbExist = checkDataBase();

        if(dbExist){
            //do nothing - database already exist
        }else{
            //By calling this method and empty database will be created into the default system path
            //of your application so we are gonna be able to overwrite that database with our database.
            this.getReadableDatabase();

            try {
                copyDataBase();
            } catch (IOException e) {
                throw new Error("Error copying database");
            }
        }
    }

    /**
     * Check if the database already exist to avoid re-copying the file each time you open the application.
     * @return true if it exists, false if it doesn't
     */
    private boolean checkDataBase(){
        SQLiteDatabase checkDB = null;
        try{
            String myPath = DB_PATH + DB_NAME;
            checkDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);

        }catch(SQLiteException e){
            //database does't exist yet.
        }

        if(checkDB != null){
            checkDB.close();
        }
        return checkDB != null ? true : false;
    }

    /**
     * Copies your database from your local assets-folder to the just created empty database in the
     * system folder, from where it can be accessed and handled.
     * This is done by transfering bytestream.
     * */
    private void copyDataBase() throws IOException{
        //Open your local db as the input stream
        InputStream myInput = myContext.getAssets().open(DB_NAME);

        // Path to the just created empty db
        String outFileName = DB_PATH + DB_NAME;

        //Open the empty db as the output stream
        OutputStream myOutput = new FileOutputStream(outFileName);

        //transfer bytes from the inputfile to the outputfile
        byte[] buffer = new byte[1024];
        int length;
        while ((length = myInput.read(buffer))>0){
            myOutput.write(buffer, 0, length);
        }

        //Close the streams
        myOutput.flush();
        myOutput.close();
        myInput.close();

    }

    public void openDataBase() throws SQLException{
        //Open the database
        String myPath = DB_PATH + DB_NAME;
        myDataBase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);

    }

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

    @Override
    public void onCreate(SQLiteDatabase db) {

    }

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

    }
    // Add your public helper methods to access and get content from the database.
    // You could return cursors by doing "return myDataBase.query(....)" so it'd be easy
    // to you to create adapters for your views.

}

Answer 1

将数据库包含在您的 Assets 文件夹中，然后查看本教程。本质上，它将数据库从 Assets 复制到/data/data/YOURPACKAGENAME/databases，您可以从那里使用平台 SQLite 类访问它。

http://www.reigndesign.com/blog/using-your-own-sqlite-database-in-android-applications/

这是普遍接受的“正确方法”，略有不同是将数据库包含在项目的 res/raw 文件夹中。