我直接在移动设备上进行开发，我有一些问题希望您能帮助我澄清有关使用数据库进行开发的问题：
我的应用程序旨在使用 SQLite 数据库（只读模式），所以我想 知道我应该将在电脑上创建的 .sqlite 文件放在哪里 订购应用程序读取甚至直接订购。
稍后，应用程序应该从a下载db文件 集中式服务器。所以，我们的想法是继续将该文件放入 同一位置，应用程序肯定会知道并可以检查它是否 在尝试使用它之前就存在。
谢谢！
您需要将 SQLite 数据库打包为应用程序的资源（例如 res/raw）或资产。但是，您将无法直接使用打包的 SQLite 数据库。您需要将其复制到 Android 期望您的应用程序的数据库文件所在的位置，然后从那里使用它。最好的方法是使用
Context.getDatabasePath(String)您需要将数据库文件复制到资产文件夹中，然后将其写入内存以使用以下代码在应用程序中访问：
public class DataBaseHelper extends SQLiteOpenHelper{
private static final String TAG = "DataBaseHelper";
//The Android's default system path of your application database.
private static String DB_PATH = "/data/data/" + Constants.package_name + "/databases/";
private static String DB_NAME = "YourDatabaseName.db";
public 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.getWritableDatabase();
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_READWRITE);
}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[2048];
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);
}
@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) {
}
希望这有帮助。
我将初始数据库放在“assets”目录中，然后将其复制到用户可访问的路径上 - 例如外部存储器（SD卡等）。我使用这种方式没有遇到任何问题:)
我建议如果您还想插入数据而不仅仅是获取值，您可以在应用程序内创建数据库
永远有路径：
/data/data/your_project_name/databases/yourdatabase_name.db
http://www.anotherandroidblog.com/2010/08/04/android-database-tutorial/