我有一个大约15MB的数据（太大，无法存储在每个设备上）的SQLite数据库。我正在构建一个应用程序来与这些数据进行交互。如何从应用程序的存储位置访问数据库。我不是要求某人为我做这件事，但我该怎么去研究如何做到这一点。是否有一个android模块在传递一个ip地址（或FTP服务器IP？）之后执行此操作？我在哪里开始研究托管我的数据库的最佳方式，然后将其链接到我的应用程序？这是如何完成的高层简介？谢谢！从Android应用程序访问外部数据库
两种方式
您可以将查询发送到Web服务器和检索结果（你需要接受查询并通过HTTP发送结果Web服务器URL）。
您可以下载数据库并将其放入应用程序数据库目录，然后您可以查询此数据库。
试试这个，
把你externalDB文件夹资产并打开此文件，并在数据库中编写，然后访问它请看下面的例子中资产的文件夹我的externalDB文件。
main.xml中
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
<Button android:id="@+id/button01"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Copy Database">
</Button>
</LinearLayout>
DatabaseHelper.java
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
public class DatabaseHelper extends SQLiteOpenHelper{
//The Android's default system path of your application database.
String DB_PATH =null;
private static String DB_NAME = "extenalDB";
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/";
}
/**
* 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) {
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();
}
Log.v("check DB", ""+checkDB);
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);
// Log.v("read", "1"+myInput.read(buffer));
}
//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) {
}
//return cursor
public Cursor query(String table,String[] columns, String selection,String[] selectionArgs,String groupBy,String having,String orderBy){
return myDataBase.query("EMP_TABLE", null, null, null, null, null, null);
}
}
Main.java
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
import android.database.sqlite.SQLiteOpenHelper;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;
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("EMP_TABLE", null, null, null, null,null, null);
if(c.moveToFirst())
{
do {
Toast.makeText(CopyDbActivity.this,
"_id: " + c.getString(0) + "\n" +
"E_NAME: " + c.getString(1) + "\n" +
"E_AGE: " + c.getString(2) + "\n" +
"E_DEPT: " + c.getString(3),
Toast.LENGTH_LONG).show();
} while (c.moveToNext());
}
}
});
}
}
竭诚为您服务。
[网络服务]（https://en.wikipedia.org/wiki/Web_service）已经存在了15年以上，是当今大多数主要网站和移动应用程序的基础。 – CommonsWare