android - 将数据库 .db 或 .sqlite 存储在 android 的资产中

Question

如何将 .db 或 .sqlite 保存在 assets 文件夹中。此时我正在这样做：

    @Override
    public void onCreate(SQLiteDatabase db) {
        mDatabase = db;

          SQLiteDatabase.openOrCreateDatabase("assets/"+DATABASE_NAME+".db", null);

        mDatabase.execSQL(FTS_TABLE_CREATE);


    }

但 openOrCreateDatabase 给出错误。我尝试使用 .db 和 .sqlite 但错误是相同的。

Answer 1

您无法从资产中打开数据库——您需要先将其复制到本地存储。

Answer 2

在这里，我给你完整的代码，如果你成功请回复

public class DataBaseHelper extends SQLiteOpenHelper{
private Context mycontext;

private String DB_PATH = "/data/data/gr.peos/databases/";
//private String DB_PATH = mycontext.getApplicationContext().getPackageName()+"/databases/";
private static String DB_NAME = "BLib.sqlite";//the extension may be .sqlite or .db
public SQLiteDatabase myDataBase;
/*private String DB_PATH = "/data/data/"
                            + mycontext.getApplicationContext().getPackageName()
                            + "/databases/";*/

public DataBaseHelper(Context context) throws IOException  {
    super(context,DB_NAME,null,1);
    this.mycontext=context;
    boolean dbexist = checkdatabase();
    if(dbexist)
    {
        //System.out.println("Database exists");
        opendatabase(); 
    }
    else
    {
        System.out.println("Database doesn't exist");
    createdatabase();
    }

}

public void createdatabase() throws IOException{
    boolean dbexist = checkdatabase();
    if(dbexist)
    {
        //System.out.println(" Database exists.");
    }
    else{
        this.getReadableDatabase();
    try{
            copydatabase();
        }
        catch(IOException e){
            throw new Error("Error copying database");
        }
    }
}
private boolean checkdatabase() {
    //SQLiteDatabase checkdb = null;
    boolean checkdb = false;
    try{
        String myPath = DB_PATH + DB_NAME;
        File dbfile = new File(myPath);
        //checkdb = SQLiteDatabase.openDatabase(myPath,null,SQLiteDatabase.OPEN_READWRITE);
        checkdb = dbfile.exists();
    }
    catch(SQLiteException e){
        System.out.println("Database doesn't exist");
    }

    return checkdb;
}
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("/data/data/gr.peos/databases/BLib.sqlite");

    // transfer byte to inputfile to 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_READWRITE);

}



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

谢谢。

Answer 3

您必须首先检查数据库文件夹中的数据库（什么都没有）

然后你必须将 .db 或 .sqlite 复制到 data/data/databases 文件夹，并且只有你可以打开数据库

这是我的示例代码：

public void createDataBase() throws IOException {
     boolean dbExist = checkDataBase();
     //boolean dbExist = false;
    if (dbExist) {
        // do nothing - database already exist
    } else {

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

}

// this method will check the existance of database
private boolean checkDataBase() {
    SQLiteDatabase checkDB = null;

    String myPath = DB_PATH + DB_NAME;
    try {
        checkDB = SQLiteDatabase.openDatabase(myPath, null,
                SQLiteDatabase.OPEN_READONLY);
    } catch (Exception e) {

    }

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

    return checkDB != null ? true : false;
}

// copy the database file from asset folder to the DDMS database folder
private void copyDataBase() throws IOException {
    // Open your local db as the input stream
    InputStream myInput = _context.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();
}

// open the database
public boolean openDataBase() throws SQLException {
    String mPath = DB_PATH + DB_NAME;
    // Log.v("mPath", mPath);
    db = SQLiteDatabase.openDatabase(mPath, null,
            SQLiteDatabase.CREATE_IF_NECESSARY);
    return db != null;
}