问题
I'm developing an application and I've run into two problems here:
How can I open an SQLite database which is stored in the assets folder? What path do I use to access the assets folder in my application? Here's what I have so far:
path = "file:///asset_folder/database.dat"; SQLiteDatabase db = null; db = SQLiteDatabase.openDatabase(path, null, SQLiteDatabase.OPEN_READONLY);How can I copy a file to the internal memory (
/data/data/...) during the installation of my application or during the first run? I want to copy a folder inside the assets folder into the internal memory during the first run.
Any suggestions would be greatly appreciated.
回答1:
I was having the same problem, so I moved the db file to the res/raw folder, and accessed it like so:
InputStream inputStream = getBaseContext().getResources().openRawResource(R.raw.mySQLiteFile);
Then I tried to move the file into the /data/data/com.mydomain.www/databases/ folder, but I would get an exception because the destination path didn't exist, so I did File(destPath).getParentFile().mkdir();
From there, I called a copy db method to transfer the db to the destination.
public void CopyDB(InputStream inputStream, OutputStream outputStream) throws IOException {
byte[] buffer = new byte[1024];
int length;
while ((length = inputStream.read(buffer)) > 0) {
outputStream.write(buffer, 0, length);
}
inputStream.close();
outputStream.close();
}
InputStream is the db file, OutputStream is the FileOutputStream(destPath).
回答2:
From this post i found this tutorial. It tells you how to deal with databases in your assets folder. That at least answers your first question. I'm not too sure about your second.
回答3:
Copy database from assets folder to data/data/database folder of your application. Use Below code.
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
import android.database.sqlite.SQLiteOpenHelper;
public class DataBaseHelper1 extends SQLiteOpenHelper{
//The Android's default system path of your application database.
public static String DB_PATH = "/data/data/com.XXX.XXX/databases/";
private static String DB_NAME = "india.sqlite";
private static String DB_NAME_MY = "india.sqlite";
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 DataBaseHelper1(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{
// for first database;
boolean dbExist = checkDataBase(DB_NAME);
if(!dbExist){
try {
copyDataBase(DB_NAME_MY,DB_NAME);
} catch (Exception 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(String DB){
SQLiteDatabase checkDB = null;
try{
String myPath = DB_PATH + DB;
checkDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
}catch(SQLiteException e){}
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(String assetfile,String DB) {
//Open your local db as the input stream
InputStream myInput = null;
//Open the empty db as the output stream
OutputStream myOutput = null;
try {
myInput = myContext.getAssets().open(assetfile);
// Path to the just created empty db
String outFileName = DB_PATH + DB;
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);
}
System.out.println("***************************************");
System.out.println("####### Data base copied ##############");
System.out.println("***************************************");
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
finally{
//Close the streams
try {
myOutput.flush();
myOutput.close();
myInput.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
public void openDataBase() {
try {
//Open the database
String myPath = DB_PATH + DB_NAME;
myDataBase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
@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) {
}
// Add your public helper methods to access and get content from the database.
// You could return cursors by doing "return myDataBase.query(....)" so it'd be easy
// to you to create adapters for your views.
}
来源：https://stackoverflow.com/questions/6751757/get-the-sqlite-path-within-the-assets-folder