数据库复制到SD卡是否存在 [英] Copy database to sdcard if exists

问题描述

我怎样才能复制数据库文件到SD卡，只要它的存在？这里是我的code：

How can I copy database file into sdcard if only it exists? Here is my code:

public boolean checkdatabase() {
        boolean checkdb = false;
        try {
            File databaseFile = myContext.getDatabasePath("database.db");
            checkdb = databaseFile.exists();
        } catch(SQLiteException e) {
            System.out.println("Database doesn't exist");
        }
        return checkdb;
    }

    public void opendatabase() {
        boolean dbexist = checkdatabase();
        if (dbexist) {
            myDatabase = SQLiteDatabase.openDatabase("data/data/***/databases/database.db", null, SQLiteDatabase.OPEN_READWRITE);
        } else {
            createdatabase();
            System.out.println("Database doesn't exist");
            myDatabase = SQLiteDatabase.openDatabase("data/data/***/databases/database.db", null, SQLiteDatabase.OPEN_READWRITE);
        }
    }

    private copydatabase() throws IOException {
            String DB_PATH = "data/data/***/databases/";
            File f = new File(DB_PATH);
            if (!f.exists()) {
            f.mkdir();
            }
            String DATABASE_NAME = "database.db";
            InputStream myInput = myContext.getAssets().open(DATABASE_NAME);
            String outFileName = DB_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();
        }

这code复制DATABSE到内部存储器。我要检查，如果外部存储器（SD卡）存在，如果这是真的 - 拷贝数据库文件到它，然后到处访问它在我的应用程序

This code copies databse into internal memory. I want to check if external memory (sdcard) exists, and if it is true - copy database file into it and then access it everywhere in my app.

推荐答案

试试这个：

try {
        File sd = Environment.getExternalStorageDirectory();
        File data = Environment.getDataDirectory();

        if (sd.canWrite()) {
            String currentDBPath = "//data//{package name}//databases//{database name}";
            String backupDBPath = "{database name}";
            File currentDB = new File(data, currentDBPath);
            File backupDB = new File(sd, backupDBPath);

            if (currentDB.exists()) {
                FileChannel src = new FileInputStream(currentDB).getChannel();
                FileChannel bst = new FileOutputStream(backupDB).getChannel();
                bst.transferFrom(src, 0, src.size());
                src.close();
                bst.close();
            }
        }
    } catch (Exception e) {
    }

不要忘了包括这在你的清单文件：

Don't forget to include this in your manifest file :

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

这篇关于数据库复制到SD卡是否存在的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！