Question

我需要在/ data / data / package-name / app_database /而不是/ data / data / package-name / database /中创建一个db怎么做？

Answer 1

请通过此How to make a database for my android app链接查看我的问题。只需要更改数据库路径...希望它能正常工作

Answer 2

首先将数据库复制到资源中，然后创建DBHelper.java并添加以下代码

public class DBHelper扩展了SQLiteOpenHelper {

private static final String DATABASE_NAME = "database_name.sqlite";
private static final int DATABASE_VERSION = 1;
private static final String DB_PATH = "/data/data/package_name/databases/";
private Context myContext;
private SQLiteDatabase myDataBase;

public DBHelper(Context context) {

    super(context, DATABASE_NAME, null, DATABASE_VERSION);
    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) {

            e.printStackTrace();
            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
 */
public boolean checkDataBase(){

    SQLiteDatabase checkDB = null;

    try{
        String myPath = DB_PATH + DATABASE_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.
 * */
public void copyDataBase() throws IOException{

    //Open your local db as the input stream
    InputStream myInput = myContext.getAssets().open(DATABASE_NAME);

    // Path to the just created empty db
    String outFileName = DB_PATH + DATABASE_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 + DATABASE_NAME;
    myDataBase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READWRITE);

}

@Override
public synchronized void close() {


    if(myDataBase != null)
        myDataBase.close();



}


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

}

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

}

}

如何在android中的/ data / data / package-name / app_database /中创建数据库

2 个答案: