Question

正如我在其他地方看到的那样，我已经完成了两件事情。该应用程序有一个按钮，说明复制和onClick它将.db文件从正在运行的apk的assets目录移动到该文件的数据库目录。

我想知道是否可以获取数据库文件并将其复制到应用程序的数据库目录而不是当前正在运行的应用程序？

或者更清楚我的问题是，有人可以给我一个示例或告诉我如何编辑下面的代码，将复制的.db放在与db拷贝时当前运行的app目录不同的app目录中并且正在进行移动？

public class DatabaseHelper extends SQLiteOpenHelper{

//The Android's default system path of your application database.
private static String DB_PATH ="/data/data/com.rtt.bltc/databases/";
private static String DB_NAME = "ldeb.db";

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;
    DB_PATH="/data/data/"+context.getPackageName()+"/"+"databases/";
    //DB_PATH="/data/data/com.rtt.bltc"+"/"+"databases/";
}

/ ** *在系统上创建一个空数据库，并使用您自己的数据库重写它。 * * / public void createDataBase（）抛出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) {

}

//返回游标 public Cursor query（String table，String [] columns，String selection，String [] selectionArgs，String groupBy，String having，String orderBy）{ return myDataBase.query（“profiles”，null，null，null，null，null，null）;

}

我已经在上面和下面附上了CopyDb和Helper类的副本。

public class CopyDbActivity extends Activity {
/** Called when the activity is first created. */
Cursor c=null;
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    ((Button)findViewById(R.id.button01)).setOnClickListener(new View.OnClickListener(){
        @Override
        public void onClick(View v) {


             DatabaseHelper myDbHelper = new DatabaseHelper(CopyDbActivity.this);
             try {

                myDbHelper.createDataBase();

        } catch (IOException ioe) {

            throw new Error("Unable to create database");

        }

        try {

            myDbHelper.openDataBase();

        }catch(SQLException sqle){

            throw sqle;

        }
        Toast.makeText(CopyDbActivity.this, "Success", Toast.LENGTH_SHORT).show();



        c=myDbHelper.query("profiles", null, null, null, null,null, null);
        if(c.moveToFirst())
        {
            do {

                Toast.makeText(CopyDbActivity.this,
                        "_id" + c.getString(0) + "\n" +
                        "UUID" + c.getString(1) + "\n" +
                        "NAME" + c.getString(2) + "\n" +
                         Toast.LENGTH_LONG).show();
                         } while (c.moveToNext());
                 }
             }
    });        
    }
   }

Answer 1

我想知道是否可以获取数据库文件并将其复制到应用程序的数据库目录而不是当前正在运行的应用程序？

没有。您的应用没有读取访问其他应用的内部存储空间部分，更不用说写入权限了。

将数据库从资产复制到单独应用程序的数据库文件夹

1 个答案: